Interview Date: August 26, 1992
Interview Location: Spring Valley, CA USA
Interviewer: Archer Taylor
Collection: Archer Taylor Technical Collection
Note: Audio Only. This tape is a replacement for the first part of the interview with Socks Bridgett on April 17, 1992, which failed to record. This part of the interview is conducted by Archer Taylor at the home of Socks Bridgett in Spring Valley, CA, near San Diego, on August 26, 1992.
TAYLOR: Okay, I believe we are on the air now. What is it you have in mind to say?
BRIDGETT: I thought maybe if we went through some of the names and got them out of the way, then that would help fill in some of the other things perhaps.
TAYLOR: All right. Oh, incidentally, did you have a chance to go through and edit the transcript?
BRIDGETT: I sent out most of that. There was not an awful lot needed in that, just a few places.
TAYLOR: There were some places I couldn’t help on.
BRIDGETT: One place where I think we may need some other things is on the 427. I tried to fill in a few schematic diagrams … you may need more. Incidentally, there is a good thing … I couldn’t find my copy. It was an instruction book that is now at the museum. I made a copy, but I can’t find my copy. They had good instructions making up a 427 in there. I did make a copy for myself, but I don’t know where I put it right now.
TAYLOR: I will be going up to State College to go through what they have up there on everybody.
BRIDGETT: If you can find that, there is a good set of instructions for making up the 427. Okay. Now some of the names here, in this, you are going to find a few of these names. Owen Hanigan is a system operator up in New England, in Maine.
TAYLOR: Is it spelled right? How is it spelled?
BRIDGETT: It is spelled right in this. He lives in Holton, Maine. I don’t really know if he operates his own system now, but he didn’t at the time this was built. He had several systems up there … Skowhegan … listed in this and you can keep that. Vince Parker operates a lot of little things up in Mount Washington. He operates WMTW. That’s channel 8 and he’s a little tyrant up there. He runs that. He’s the de facto coordinator up on Mount Washington.
TAYLOR: I see, he’s it.
BRIDGETT: He’s it. Harmon White an MSO up in … His name is in this, too. He runs Laconia, systems around Nashua and quite a few others up in New Hampshire. Win Bemis was a field engineer at SKL.
TAYLOR: I may have met him, but I can’t place him.
BRIDGETT: You may not have met him, but there have been a lot of people up around the Midwest that would know him pretty well as a field engineer. Dick Berwyn was the man doing the CATV for SKL when I came on board and he left shortly after.
BRIDGETT: Yes, an engineer. He is a top engineer in the field of audio now. He is well known there. George Ray was one of the best engineers at SKL. Stayed right through till the last gun was fired and I think now he is running his own consulting business.
TAYLOR: Was he there before you were?
BRIDGETT: He was there. He was one of the first engineers hired there, I believe.
TAYLOR: Before you were there?
TAYLOR: Was this when Don and Fritz were running the laboratory equipment, before they got into CATV?
BRIDGETT: Yes. In fact he stayed pretty much into … He didn’t do an awful lot on CATV. He wanted to stay in instruments … that was his main love, instruments.
TAYLOR: Did SKL do quite a bit of that after they got into CATV or did it peter out?
BRIDGETT: We still did some but CATV tended to take over an awful lot but he had a hard time staying with what he liked to do.
TAYLOR: Too bad he didn’t get into instrumentation like Ken Simons did, because there was a great need.
BRIDGETT: He did start to, but I have not kept up with him an awful lot, so I don’t really know. He did go into some consulting, and do some specialty work on one of the things. The last time I talked to him he was doing some security work for the wheel wells for airplanes and so on. That was the last thing I remember talking to him about. George Wayne was one of the guys who was going to be an angel for SKL. He sold out a company called Wayne George that had made quite a bunch of money during the war on aiming for radar and artillery and so on.
TAYLOR: Wayne George?
BRIDGETT: Wayne George was the name of the company, and George Wayne is his name.
TAYLOR: Oh, he just turned it around?
BRIDGETT: At the end of the war he was able to sell that out before that business went to hell.
BRIDGETT: Nick Sangueneti was in this.
TAYLOR: I know that name.
BRIDGETT: He owned the Barre, Vermont system. Let’s see, are there any more names here? I think I’ve got most of the names here. Oh, ADS … George Ray. After SKL folded, he and one or two other of the engineers and people at SKL, formed a company … ADS–Amplifier Design Services–and they did the first feed forward design. SKL never did a feed forward.
TAYLOR: This was after SKL was sold?
BRIDGETT: After SKL was sold. George Ray had wanted to do a feed forward, and I tried to discourage him. It seemed to me it would be too difficult to control phase and amplitude over that bandwidth, and he did it like that. (Finger snap)
TAYLOR: That was when Bill O’Neil got …
BRIDGETT: Bill O’Neil and George Ray formed ADS.
TAYLOR: Was Bill with SKL before that?
TAYLOR: Had he been for long or was …
BRIDGETT: Bill O’Neil, I think he was one of the Northeastern co-op students. He came in about the same time as Brooks.
TAYLOR: Oh, I see. I met him, but I only met him after the SKL was transferred over and I didn’t know where he came from or …
BRIDGETT: I think that’s where … with Bill O’Neil. We had several people who came in that way. Bob Brooks came in that way.
TAYLOR: You told me that.
BRIDGETT: And two or three others. There was one other that stayed in but didn’t get in the CATV business part of it. Bill O’Neil did get into that and, I think, he did take some time going down to Scientific Atlanta. Course they wanted to take the people down there, but George Ray wasn’t going to move out of New England, that’s all there was to it. And Bill O’Neil didn’t really want to, but he gave it a try for a little while, I think.
TAYLOR: When Bill and Roger Wilson formed a company on optical?
BRIDGETT: Yes. Incidentally, the first optical is fiber optics and George Ray, Bill O’Neil and a couple of others did some work for …. Oh, what’s his name?
TAYLOR: Irving Kahn?
BRIDGETT: Irving Kahn, on amplifiers. And he bought them out and then he folded. Of course they were doing pretty good on the amplifiers then.
TAYLOR: They were also marketing the Colorburst amplifiers 7000.
BRIDGETT: Yes, they did manage to keep that and they were doing a nice little business on that.
TAYLOR: Then when they sold to Scientific Atlanta, they sold the rights and particularly the housing … one that had a couple of cavities in it.
BRIDGETT: That’s the one.
TAYLOR: Our transcriber got a kick out of that. In fact, she didn’t know what she was writing I think!
BRIDGETT: Yes, I’ve got the names all together. I thought that would be a quick one to …
TAYLOR: Very good. What I didn’t do to start with, I think, was to get a little fill in on your background. Why don’t we get a little of that in here now?
BRIDGETT: Okay. Date of birth, October 12, 1916. Parents … just ordinary. My father had been a sign painter and ended up as a warehouse foreman. My mother …
TAYLOR: Where was this? Was this in Woburn?
BRIDGETT: No. I grew up in Quincy, Massachusetts, and I have one sister. I graduated from MIT, finally in 1946; in the class of ’37 originally but the war came along. I got a BS in mathematics, actually with a minor in Physics. I never really knew what I wanted to be. I wanted to be a scientist and was interested in engineering, and radio ham, and all this kind of thing, so it looked liked mathematics was the best thing to do.
TAYLOR: It’s interesting to me how many of the engineers that I’m running into now in television and cable business, were physics majors … physics and mathematics and one chemistry. Bob Powers, who was the chief scientist for the FCC for a while, was a PhD in chemistry … not chemical engineering, but chemistry.
BRIDGETT: Well, actually I grew up with several of my friends who were interested in various things like physics and chemistry. My real buddy in high school and junior high school, was Robert Woodward. I don’t know if you know who he is … Nobel Prize.
BRIDGETT: Robert Burns Woodward.
TAYLOR: The name is very familiar but I don’t …
BRIDGETT: So that’s the bits from there anyway. Employment before SKL was kind of varied inasmuch as I had to drop out during the war. I ended up designing the electric distribution system up at Fort Devens prior to going to the war.
TAYLOR: Sound distribution?
BRIDGETT: Electric power distribution. I taught radio and operation and stuff in the Maritime service. Then I went into teaching physics at Franklin Technical Institute in town there and sort of thought I’d liked to teach for a while. And then I decided, “Well, maybe I should go back to engineering,” and that’s when I dropped into SKL once.
TAYLOR: What were you teaching?
BRIDGETT: Teaching physics.
TAYLOR: When did you drop into SKL?
BRIDGETT: It was in 1951 I decided to go back to engineering.
TAYLOR: How did you know about SKL?
BRIDGETT: A fellow that I was teaching with had heard that there was a job there and so I dropped in to see what it was about. Talked with Lester and Fitz Kennedy. They described it, and I went home and thought it over, and thought “they can’t be talking what they said.” They’re talking about wiring apartment houses and hotels … they’re not talking about wiring whole towns. That’s not economically feasible. So I went back and asked them and they said, “Yes, that’s what we’re doing.” So I said, “Well, it sounds crazy enough. I want the job if you want me.” So I took it.
TAYLOR: You mentioned Lester was the one you talked to … Lester and Fitz. Now Don, was he there at the time?
BRIDGETT: Yes. Well, Don was not actively there. He was still more or less involved in financial matters, not for just SKL, but other things.
TAYLOR: I see. So Fitz and Lester were really the ones that …
BRIDGETT: Lester had just come aboard I guess, because he got his masters degree in 1950 at MIT. He had worked at RCA for some time before that and I guess it was Georgia Tech or somewhere he got at his bachelor’s. And then he had worked at RCA.
TAYLOR: So Fitz was the one that goes back the farthest?
BRIDGETT: Yes. I don’t know the exact date that it started, but I gather it must have been around 1948.
TAYLOR: That was in the laboratory instrumentation?
BRIDGETT: Yes. I do know that as I can reconstruct things now … mostly young engineers, as they got George Ray and Hap Horn, and a few others, they graduated …
TAYLOR: What was the second one?
BRIDGETT: Harrison Horn was one of the engineers who …
BRIDGETT: H-o-r-n. Harrison Horn was …
TAYLOR: Harrison Horn, okay. I am trying to get this on here for spelling.
BRIDGETT: Yes. And a few other names I don’t remember right now but they graduated in 1949 from MIT. So they all came around that same time.
TAYLOR: Was Fitz from MIT also?
BRIDGETT: I don’t know where he came from. I looked him up in the MIT register to try and get some of these dates together. And around that time, Submarine Signal Company folded up and they got most of their assembly help from there. The girls all came from there.
TAYLOR: Was that in Cambridge?
BRIDGETT: I don’t know. No, that was down near the harbor, I think, in Boston.
TAYLOR: In Boston?
BRIDGETT: I think that’s where the submarine signal people came from. Freddie Mars (?) was the foreman.
TAYLOR: Franklin Institute where you taught, was that in Boston?
BRIDGETT: That was in Boston, yes, and still is. That was established by Benjamin Franklin in his will.
TAYLOR: My wife graduated from the Benjamin Franklin School of Accounting, but that was in Washington.
BRIDGETT: It must have been right around that time that it started, you see, that paper that I showed you here from Electronics Magazine. That was in 1948 I think, wasn’t it?
TAYLOR: September ’49.
BRIDGETT: So yes, that was done for publicity purposes, while they started that obviously. That was before the 212. That was the first pulsed amplifier, used for oscilloscopes. So just around…
TAYLOR: How is this different from the 212?
BRIDGETT: That was a straight 200 MHz one for pulse purposes, attached to an oscilloscope.
TAYLOR: I see.
BRIDGETT: That was a single stage one. They came out with the 202, which had two of those same stages.
TAYLOR: I see.
BRIDGETT: That’s one of their early products. So that would be just about the time it started. I’d say 1948, I think.
TAYLOR: Then the 202 was two stages of this?
TAYLOR: And then there was the 211 wasn’t there?
BRIDGETT: No. 212.
BRIDGETT: No, 211 came quite a bit later.
TAYLOR: Oh, I see. We’ll skip the 211 for a minute then. The 212…
BRIDGETT: The 212 I also finished up. That one was designed for CATV. I think I know who started that. It was a young fellow named Charles Kennedy. Chuck Kennedy, a teacher who …
TAYLOR: No kin to Fitz?
BRIDGETT: No. But he was part-time, and I worked part-time with him in the fold-over time. I was working part-time with him when he started. I was still teaching part-time, and he was working with these people part time. You know, of course, he left when Lester would have come in … when they wanted a full time chief engineer in 1950. So I can piece, even though I wasn’t there at the time, I can piece the times together.
TAYLOR: But the two, this amplifier, and then the two stage 202, were before any of this? And these were strictly oscilloscope pulse amplifiers. And then that was modified in some ways to …
BRIDGETT: Physically they were different.
TAYLOR: What had to be different?
BRIDGETT: They had to widen the bandwidth, and then they tried to make it a …
TAYLOR: … because this says 200 megahertz?
BRIDGETT: Yes, they had to expand it to …
TAYLOR: They didn’t want to go beyond 216, really.
BRIDGETT: They went to 220 to be sure.
TAYLOR: 220 to be sure, yes.
BRIDGETT: I mean, I made sure when I finished up that it would have plenty of room at the top end to be sure it would take channel 13.
TAYLOR: Elbow room …
BRIDGETT: Yes. 220 was the spec end of it.
TAYLOR: What else did you have to do with it? Was there automatic gain control?
BRIDGETT: Well, that had to come after …
TAYLOR: That was later?
BRIDGETT: Yes. This was just to get a good stable amplifier that would run up through 216 and to spare.
TAYLOR: The first one of those was called 212, is that …
BRIDGETT: The 212, was the first CATV amplifier.
TAYLOR: Put a “1” in instead of a “0” on the 202. And then later than that came the 211.
BRIDGETT: The 211 was designed strictly to satisfy AT&T.
TAYLOR: Western Electric?
TAYLOR: Was that electrical specs as well as mechanical, because they had fairly elaborate mechanical specs, too?
BRIDGETT: Yes. Mainly they wanted something that … they figured they just wanted to come up over the FM band and so we designed that for them.
TAYLOR: You say they only wanted to get over the FM band?
BRIDGETT: They didn’t really want to go to …
TAYLOR: They didn’t want to go to the high band?
BRIDGETT: Yes. They didn’t have a use for it then. They were convinced that nobody would ever need that many channels.
TAYLOR: Some of the rest of us thought that when you get to 30 channels “who wants any more than that?”
BRIDGETT: That’s right.
TAYLOR: Now, who wants 150?
BRIDGETT: It was really an interesting thing, when they wanted to … I think it was Hagerstown that they wanted. It was somewhere down in Maryland, anyway, working with the Western Electric, Bell Labs and AT&T on that one. And it was a nice gang we worked with down there.
TAYLOR: Now, is this a copy I can keep or do you want a copy of that?
BRIDGETT: That is my only copy, but I don’t mind if you keep that. In fact, I kept wishing I had that to give to you, and I found I did have a copy of that!
TAYLOR: Well, I will try to remember to make a copy of this.
BRIDGETT: Okay, now, let’s see. You wanted the rest of some of this. Okay, you’ve got my employment before SKL and how I got to SKL and what did I do after I left SKL? Well, I left SKL just about the time SKL … I think just a little before it folded.
TAYLOR: Didn’t I remember from the transcript, that you left for a period in between there?
BRIDGETT: Yes, in between … about the time when we were pretty sure Pierre was going to be chief engineer. Lester, of course, wasn’t going to stay on anyway, and so he, Wyn and I formed this company … Imaging Instruments.
TAYLOR: That name is what?
BRIDGETT: Image Instruments, Inc.
TAYLOR: Okay, I’ve got that.
BRIDGETT: So we left and formed this company. Actually, Lester was a good engineer, but unfortunately, Wyn and I put him in as president, and he was not a good businessman at all. So finally, that folded.
TAYLOR: What was your product?
BRIDGETT: Well, we had big ideas and we could have made them because we made a name for ourselves in storage tubes, image storage tubes … products using image storage tubes. And we got some good fat contracts.
TAYLOR: What kind of companies?
BRIDGETT: Well, it was a Raytheon storage tube. We had some good government contracts.
TAYLOR: Did you?
TAYLOR: Signal Corps? Army?
BRIDGETT: No, actually I forget what particular things. Often they were super secret ones but we had tying in various imaging through radar, infrared and matching different types of images up. And, of course, with image storage, we could do all kinds of things. The only trouble was Lester was a great salesman when he wanted to be. But once we had some money rolling in, he stopped selling … not until we had to sell.
TAYLOR: Were your customers primarily government customers or did you have …
BRIDGETT: Unfortunately, yes. Once we got some of those done, we could have done great otherwise, too. Well anyway, that is what happened and then we had to go out hat in hand. Well, Wyn and I did … Lester could raise money … Wyn and I went back to SKL and Lester kept the thing running for a few more years … raising money.
TAYLOR: He kept the image company going?
BRIDGETT: He kept it going … raising money, selling stock, borrowing money. I don’t know how he did it.
TAYLOR: You went back to SKL after Pierre was doing something else?
BRIDGETT: Yes, after he was gone. That’s the story there.
TAYLOR: When was it that SKL finally gave up?
BRIDGETT: It was shortly after 1969. It was folding anyway and they were letting people go. Jake was chief engineer and he told me that I was going to be able to stay and I thought, you know, that was fine. But by this time, I was thinking I should be leaving anyway and people had been telling me that I should go into consulting. So, it was George Wayne who was the man who was going to save the company. He was all right, but he gave me a hard …
TAYLOR: George Wayne?
BRIDGETT: The Wayne George man, you know.
TAYLOR: Oh I’ve got that down as “Wayne” or “Wing”?
BRIDGETT: George “Wayne”.
TAYLOR: Okay, I’m just …
BRIDGETT: Okay, I guess I must not have pronounced it too clearly.
TAYLOR: I just want to be sure that I get it right.
BRIDGETT: At any rate, he did something that kind of annoyed me at one time and I just told him, “I’m sorry, I’ve got to go.” At just that time George Duffy was starting up his operation and he was convinced he needed a full time engineer and I told him, “Well, you don’t.”
TAYLOR: Now what was Duffy? That’s a …
BRIDGETT: Colonial Cablevision.
BRIDGETT: Colonial Cablevision.
TAYLOR: Okay, that’s different from Colony?
BRIDGETT: Yes. Colony was a Providence and they bought a good part of Colonial.
TAYLOR: Oh, I see.
BRIDGETT: So, that’s another combination story. At any rate, he said he needed a full time chief engineer and I said he didn’t. And he couldn’t afford to pay a full time engineer, either. So …
TAYLOR: This was for the cable operation?
BRIDGETT: The cable operation, yes. You don’t need a full time engineer when you only have a couple of systems. So, I agreed to work full time if I got some part of the operation … which turned out pretty good. It turned out that I worked full time for a lot longer than I had planned on.
TAYLOR: Working for Colonial?
BRIDGETT: Yes, working for Colonial. I ended up getting a bigger piece of it than I had planned on, too, which was nothing wrong with that.
TAYLOR: That’s all right, too.
BRIDGETT: Yes. So, that is the end of that, up to that point. So, what’s missing now? Did I work at the Mass Avenue facility first? Yes.
TAYLOR: That’s where you started then?
BRIDGETT: Yes, I started there.
TAYLOR: When did they move over to Soldiers Field?
BRIDGETT: Let’s see. Seems to me I was away at the time when they moved over to Soldiers Field.
TAYLOR: As the way I see it, that was probably about the time that Pierre was there, then. It must have been …
BRIDGETT: Yes, it must have been. Because, I … actually, that was a very pleasant time up there, on Mass Avenue.
TAYLOR: Where was it on Mass Avenue?
BRIDGETT: Across Mass Avenue from MIT and back a couple of blocks.
TAYLOR: In Harvard area, right near Harvard square?
BRIDGETT: Not even as far up as Central Square.
TAYLOR: Oh. Long time since I’ve been there, but …
BRIDGETT: It was over a bar … a loft building… a big floor above a bar. Until they put in some extra ventilation, it was terrible in the summer. But anyway, it was a marvelous place to work and a fine bunch of people to work with. I can’t imagine a better group.
TAYLOR: How big an organization was it when you first joined them?
BRIDGETT: Well, let’s see, we had probably seven or eight engineers, and probably about the same number of technicians. And then I would guess, maybe thirty assembly workers.
TAYLOR: And they were all in this operation on Massachusetts Avenue?
BRIDGETT: All on this one big floor, yes. We had one corner for engineers, and it was a real fine group.
TAYLOR: You probably subcontracted out sheet metal work, and things of that sort.
BRIDGETT: No, no.
TAYLOR: You did all that yourselves?
BRIDGETT: That’s right. We had a Lindy Hanes … sheet metal worker.
BRIDGETT: Lindy Haynes.
TAYLOR: Lindy Haynes?
BRIDGETT: Yes. And he really … I’ll tell you, we couldn’t have made the 212 without a man like him. Now, the reason we could make it so precise …
TAYLOR: Let me give you a pad so I can save it for posterity.
BRIDGETT: The socket holes were punched very precisely for the 6AKS tubes, and they were put in absolutely precisely … they fit perfectly, the sockets did. And you had your pins like so, now the coils, springs, silver plated springs, that just snapped in place so that they were exactly the same length, always. Exactly the inductance we needed. So they came in, possibly it would be like this, so you always had exactly the inductance you needed. That was because, when he stamped those holes, they were exactly …
BRIDGETT: Precise. Those delay lines then, were exactly the impedance we wanted, exactly the way we wanted and all you did was that you made sure you ordered the exact number of turns, exact diameter. They just snap right in and you got the delay lines with the exact impedance you wanted.
TAYLOR: Just looking at it, it’s a very simple circuit.
BRIDGETT: A very simple circuit, but you know …
TAYLOR: But a lot of engineering goes into it, but it’s extremely simple, yes.
BRIDGETT: But you know, I’ll tell you, I spent a long time doing that, because we had … When we first did that, you had no sweep generator circuits or anything. What you did, was you measured impedance of the end with an impedance bridge, and you plotted against frequency one point at a time, and then you made a change and then you repeated this, and I thought Lester … we ought to be able to do with sweeps. You know, sweeps are something that a guy on a bench, fixing a TV or something. They were not precise at all. But I did manage to get that, it was a Kay sweep, using klystrons, I got one. We were able to calibrate precisely, and oh did that speed it up. And then, now a days … the kind of sweeps we have … in fact, years ago even we had better sweeps.
TAYLOR: The instrumentation we have got now a days, is out of this world.
BRIDGETT: Boy, I have notebooks with plots of this that you wouldn’t believe. The time it took to do it. But hey, when it was done, you had a precise product.
TAYLOR: That’s right.
BRIDGETT: And there’s nothing like … that when I was away, they made the 222 amplifier, a piece of junk. Compared to this, it was a piece of junk. But the trouble was that they made the coils too big when they stretched them. A thing like that, you couldn’t tell what you were doing when you were stretching them, you got interactions between these things … there is nothing you can do … even though you have a good sweep, what are you looking at? You know you’ve got reflections at every junction here. There is nothing you can see on a sweep that way. What you’ve got to do is to – what we did do, that I developed was a dummy that you put in the tube socket and TDR, with reflectometry you could see what was happening in each junction. Then you could do things, too.
TAYLOR: You had TDR back in those days?
BRIDGETT: We had TDR back in those days. That big scope that you saw there, this one, you could get to within one nano-second, then you could do things!
TAYLOR: This was one that you guys built?
BRIDGETT: That was one we built, (mainly George Ray) and we were able to get hold of an EG&G scope … travelling wave scope.
TAYLOR: So SKL made oscilloscopes scope, as well as …
BRIDGETT: No, I think we made only three. We sold two and we had one for ourselves.
TAYLOR: Small volume product.
BRIDGETT: Yes. The big thing is, with TDR, you could do things with this and see what was happening at each juncture. If you were putting the wrong coil there, you would see a reflection at the point and you could tell … you know, you couldn’t always tell what was happening, but you would take a tiny piece of metal on the end of a poly rod, and find out if the reflection was, if it had a reflection there.
TAYLOR: And you’re talking now about the 212 design?
BRIDGETT: Yes. Back then it was the 212.
TAYLOR: And this was about in the 50’s still or was this in the 60’s?
BRIDGETT: This was in the early 50’s … ’51, ’52.
TAYLOR: Gee, I didn’t know they had TDR in those days.
BRIDGETT: It wasn’t something that …
TAYLOR: Pulse TDR?
BRIDGETT: Yes, we had these pulse generators (also designed by George Ray) that had tenth of a nano-second rise time. Yes. I think it’s in the thick book there.
TAYLOR: In here?
BRIDGETT: I think it’s the blue book up under your arm there.
TAYLOR: This one?
BRIDGETT: I think it’s in there.
TAYLOR: Okay. Collins and Williams. That’s AT&T. Yes, Bell Labs.
BRIDGETT: Now that TD … that pulse generator, is something George Ray designed and built, when it first came out. In the blue book, this one tenth nano-second rise time pulse generator – with that, you could do real good TDR.
TAYLOR: This is the basis probably of the Collins and Williams paper that was later published in the IEEE.
BRIDGETT: I wouldn’t be surprised, yes. But see, you know, the fact is, that first type of thing I did, measuring input impedance at the end of these lines, at the individual frequencies, you put TDR on that, you’ve eased your work tremendously. And that little pulse generator that George Ray designed made all the difference.
TAYLOR: Was that done for your purposes, or did you make it for a product?
BRIDGETT: He designed that as a product.
TAYLOR: Product. You got some use out of it.
BRIDGETT: Yes. You can see why he was interested in his kind of work when he was making things like that. You can see why I had a great time working with a guy like that, too.
TAYLOR: This is one of the fall outs of radar work during the war, isn’t it?
TAYLOR: Because I remember in the late thirties, when I was at the Bureau of Standards, we were doing pulse equipment, because we were doing ionospheric studies. We were sending a pulse up to the ionosphere and measuring the time. And so I was designing IF amplifiers with fast rise time and so on. I talked to a classmate of mine and we found out that we were talking the same kind of problems, and he wouldn’t tell me what he was doing. But later (he was with the Naval Research Lab at the time) it turned out he was working on IFF, friend or foe.
BRIDGETT: Tell me, you go into labs, and you are working so much on the same kind of things, and you find you are using the same kind of slang terms, and so on.
TAYLOR: That’s right. And the fact that there is confidential, secret, doesn’t make a difference, because you’re talking the same language.
BRIDGETT: And you’ll see the same kind of black box on the bench.
TAYLOR: Exactly, and you talk about it a while, and you both made the same mistakes.
BRIDGETT: The fact is, that if they didn’t have things like that, I could have never finished that 212 as quick as I did. I mean, if I had to go through it all the same way – setting frequencies, measuring impedance, and then plotting this, and then trying to figure out, “Now, what does that mean about this?”, I would still be working on it!
TAYLOR: I’m interested. I think when I talked with you before, you talked about a solid state transmission line, distributed line amplifier. Never really came to pass, I guess.
BRIDGETT: We did sell some. It needed a lot more work before it was released.
TAYLOR: So why do you think that has never been popular in the industry?
BRIDGETT: Actually, it wasn’t needed. The fact is that the solid state amplifiers didn’t need that. It was just an idea that I was able to make it, and it needed more time to be developed. And if I had more time, I’d have found that I could have done it other ways.
TAYLOR: It wasn’t needed because the solid state transistors are low impedance devices, and you didn’t have the sort of problem you had …
BRIDGETT: But Jim Grabenstein, down in Cumberland, liked them anyway, and he bought some of them.
TAYLOR: Oh, did he buy a distributor line?
BRIDGETT: He bought some of those, yes.
TAYLOR: I know he was real hot on the “feed forward.”
BRIDGETT: Oh, feed forward, of course. And when George proved that you could really control feed forward, I fell over backwards and just admitted, “Hey, you did it!”
TAYLOR: That was George Wade?
BRIDGETT: George Ray. It was like I kept telling him, “Oh, you can never do it.” And then one day, when I walked into ADS, he said, “Come on over here, Socks. I want to show you something.” And all he had done, he had taken two 212’s, nothing fancy, and some delay lines, and coax …
TAYLOR: And some couplers …
BRIDGETT: You know, when you stop and figure it, what more precise delay lines can you have than pieces of coax?
TAYLOR: That’s right. That’s exactly right.
BRIDGETT: No problem at all.
TAYLOR: In fact, a number of years ago, when you bought a delay line, that’s what you got. It was a piece of coax.
BRIDGETT: That’s right. So all he did was he measured them off, cut them, stuck them in there, and it worked! And actually, they did sell a few of those. It’s just apparently enough people didn’t realize how good it was and so they stopped selling them. And so the only one was that kluge they were selling, Century 21, wasn’t it?
TAYLOR: That was just “Century”.
BRIDGETT: Yes. When I told Harmon that was what he had to buy, and I saw the first ones that came in, I said, “Well, I guess they work, but it’s an awful kluge. Hope you never have to repair one!”
TAYLOR: That Century device had a lot of problems with it.
BRIDGETT: To go on, to make lumped constant delay line, when you could cut a piece of coax, was ridiculous!
TAYLOR: Of course, they are lumped now days. In fact, they are being built into hybrid gain blocks, now.
BRIDGETT: Yes. Well actually, I think the first one that came out was a pretty decent one, after ADS stopped making them, was C-COR.
TAYLOR: Right. Now Joe Preschuti, did you know Joe?
BRIDGETT: I think I did, yes.
TAYLOR: Jim went through several chief engineers. Joe was the guy there at the time of feed forward. He wrote a very perceptive paper, I think, about it, because he was showing both the good and bad features of feed forward. The problem at that time was, people would get a null and think they had it all locked in, and they would sell it on the basis of that null. But then temperature would change, and all kinds of things would change and it wouldn’t stay …
BRIDGETT: That was the thing that ADS had. They had a trimmer to get the null, on their delay lines, just a single capacitor. And what they would do, they would set that so that they would be on one side of the null on one amplifier, and the next one would be on the other side. So as temperatures changed, it would bounce back and forth, and you would have one amplifier that would be better. Now that one would be a little worse, so that the whole line of amplifiers would constantly wobble about the best situations.
TAYLOR: Just as an aside, one of the big developments in modern cable TV is the AM fiber … amplitude modulated laser. We always thought a laser was either on, or it was off. But in between the off position and the on position, there is a curve. And if you could get it to operate on that as an operating line, you can get quite good linearity out of it. Well, I got talking with, I think it was C-COR, one of the manufacturer’s about how you know it looks like it has to be very precise to stay in there, and so they have to put temperature controllers – they put in, oh, these electrical cooling circuits, to cool it, to maintain a very precise temperature for the thing, otherwise, they won’t work! It was really amazing that they made that work. But that’s one of the things that cable TV has done, that Bell Labs has finally decided that was a good idea – AT&T are now using it – but up until the mid-eighties, everybody said that you can’t amplitude modulate – not linearly modulate, a laser, satisfactorily – and get enough linearity out of it. By golly, now we are putting as many as 60 or 80 channels on, and holding the IM down, so it isn’t too bad.
BRIDGETT: Well, one thing I’ve learned is that, when it comes to precision, and somebody says “you can’t”…
TAYLOR: It’s the most dangerous thing to ever say, “It can’t be done!” because some dumb guy is going to come along, who doesn’t know you can’t do it, and he’ll do it!
BRIDGETT: There is always some way you can make things a little more precise. It’s like this thing here I was showing you. Lindy Haynes just made things real precise and, it was inexpensive equipment. You’ve seen these machinists, that put a little shim here and a shim there, and that was the kind of guy he was – always could do something better.
TAYLOR: Like when I was a kid, I really always wanted to be an engineer. An engineer to me meant that you built these bridges – and then you built a bridge from both sides, then they would come together, and would match and you put the bolt in … I always thought that was the most wonderful thing in the whole world! It wasn’t until later, that I discovered that they had 12″ long oval holes – to make them work! Let’s see, was Don the finance … did he finance the original SKL?
BRIDGETT: I really don’t know about that. I do know he … there was a … I forget the guys name, he had something to do with Ryerson Steel, I think – one of the angels there.
End of Tape 1, Side A
TAYLOR: Okay. We are on Side B now. Before we started the recorder, we were speaking about the RCA Antennaplex amplifier which you thought has 50 dB gain.
BRIDGETT: They were selling the idea that they had 50 dB gain or something.
TAYLOR: I knew that they had high output of 60 dBmV output that they were claiming which would be a lot more output on 75 ohms, and I know RCA had more than one volt, maybe 5, or maybe even 10 volts output. But I didn’t know that any of them had that high gain, and that’s what surprises me.
BRIDGETT: Another thing on top of it – it’s basic with this too, this was the big thing course was – we just knew you couldn’t do it.
TAYLOR: I talked to Hank Diambra and he told me he has almost a warehouse full of everybody’s old catalogues from way, way back. So, when I get a chance, he’s on vacation now, but I will go over and see him.
BRIDGETT: Yes, because I would just love to see some of Jerrold’s old literature that pumped channel – drawn on (?) catalog sheets and so on, that literature.
TAYLOR: That is a real, real find. He says he’s kept everything, and he had it in offsite storage for a while, but then when he moved to where he is now, he built a warehouse and he’s got this stuff all in boxes, and I guess sorted, and maybe even cataloged. So, I’m just looking forward to have the chance to get my hands on it.
BRIDGETT: That would wonderful to get some of that stuff.
TAYLOR: The arrangement ought to be made at State College for that to be cataloged and properly handled. He ought to keep it until it is, otherwise it will just get …
BRIDGETT: I’m wondering if I did the right thing sending some of that down at the time I did.
TAYLOR: I think that they’re taking care of… The problem they are having now is, people are taking stuff out of their system, and they send truck loads of stuff up to State College…
BRIDGETT: That’s the type of thing – when I saw this thing come in …
TAYLOR: Yes, I got a copy of that.
BRIDGETT: Let’s see, this is the sort of thing, according to, they pointed out Joe Cost pushed it and has a display on it, because he knew what it was. So, I thought, well gee, all this stuff I sent down, nobody down there knows what it is – it will get stuck on a back shelf somewhere, gathering dust. And that’s when I began thinking that I want someone to hand carry that into that place – I don’t want … because nobody will know what that is, unless they…
TAYLOR: Right. It will have to be described.
BRIDGETT: Wait a minute, what’s this? Oh, this is about what you are doing right now.
TAYLOR: Yes, she called me by telephone and asked me what interviews I had done.
BRIDGETT: I saw my name and Jake’s, so I wondered what this is about.
TAYLOR: I’ve had trouble with them. I came to Jake Shekel’s name and the way it came out in one of their publications – he would never have recognized it. I finally figured out who it was – it didn’t look anything like Jake Shekel. What I thought was written was “Socks” as your nickname.
BRIDGETT: Well, the other one I would recognize would be just “Socks” but this “Sock”…
TAYLOR: Apostrophe “s”
BRIDGETT: And then of course, a lot of people put “e” on the end…
TAYLOR: I did that too, until I discovered I was wrong so I … a couple of the letters I sent you had an “e” on them.
BRIDGETT: I was supposed to see Joe Cost but that he didn’t know what to do with it.
TAYLOR: Joe Cost – “C O S T”?
TAYLOR: And he was at SKL?
BRIDGETT: No, he was a salesman from … I forget… I happen to know him because he was dropping in on us at Colonial.
TAYLOR: The coring tool. Joe Hale told me he got the idea from AMP, the AMP connector manufacturer.
BRIDGETT: I think he was with AMP.
TAYLOR: That seems to be where the idea of the sleeve came in. I think I may not have gotten your comments about the distributed amplifier patents. Maybe you better put it in your own words about the personal patent.
BRIDGETT: Yes. As I understood it, there was a British patent, a man named Percival on the distributed amplifier and Fitz Kennedy had written permission from Percival to use the patent. And that’s as far as I knew that was there – now, as far as anyone else using this, it was, I believe International Telemeter had constructed, and I had seen a model of that, that had been built presumably as a distributed amplifier but whoever had built this, had no idea how this thing worked – because it had an output on both ends of the plate line and of course, that couldn’t work.
TAYLOR: I guess what I recall Fitz Kennedy telling me that the fellows at International Telemeter had infringed his patent – which was probably faulty memory on my part and he was probably speaking of the rights that he had acquired that to use the patent and saying that the International Telemeter people just didn’t bother getting it.
BRIDGETT: Getting the rights to use it?
TAYLOR: Going through that procedure.
BRIDGETT: As I understood it this Percival really wasn’t anxious to cause any trouble about it because he was just happy to see it used.
TAYLOR: As long as he got full credit?
BRIDGETT: Yes. When this monstrosity showed up at SKL we all looked at it – we just hooted (?) at it.
TAYLOR: You guys were unquestionably the experts in distributed amplifiers and that was always true. Jerrold tried to copy it – tried to use distributed amplifier – it never took off – I know don’t know if it was because it didn’t work very well or what but it didn’t ever get a product that was comparable. And International Telemeter of course did it early, very early because we got it in 1953 and we had tried RCA and couldn’t get Jerrold because of the service contract and we used the International Telemeter – if we had used it right, it would have been at least workable and the one we finally found that worked for us, was Blonder-Tongue’s MCA – that was a split band amplifier – a low band-high band; we only needed a low band.
BRIDGETT: Actually, these were a lot of little gimmicks that you had to pay attention to – to get a workable one. In fact a lot of them are referred to in this paper. Just a plain low pass – LC line has some problems – you can’t just do that. The fact is that is that image impedance could give you some problems: at cutoff you reach a high impedance and if there’s any coupling between output and input lines, you get oscillation. That’s just the first problem you run into.
TAYLOR: Socks is referring to a paper by HG Rudenburg, Harvard and Fitz Kennedy – SKL. Did you have ties with other people in Harvard? You were right on top of them there at Soldiers Field.
BRIDGETT: I don’t specifically remember. We did have MIT and we did have ties with people there.
TAYLOR: F.E. Terman was at Harvard – I don’t know if you knew him or not. He was one of the big-maybe Chairman of the department. Harvard had quite an Engineering School.
BRIDGETT: Yes, they did. In fact, I guess quite a lot of interplay between the two schools.
TAYLOR: Harvard and MIT?
BRIDGETT: Yes. In fact, there was a time when you could be registered in one school and that would give you the rights to attend classes in the other one. Almost as easy as that.
TAYLOR: I was just trying to remember what was on this tape I didn’t record. Did we talk about the 50 db gain and the 80 db gains on this?
BRIDGETT: We did, but we didn’t reach any firm conclusions.
TAYLOR: Okay. Actually we got into talking about Hank Diambra’s catalogs. It would be very tough to find out if they really had…
BRIDGETT: Of course I’m not really sure that I actually saw literature to that effect -I do know that I heard reports back from a field trip, that’s for sure.
TAYLOR: As earlier as I … for example, Vic Nicolson was doing training programs for Jerrold and that’s when I first met him – probably late 50’s and they were talking 22 db gain, 21 db gain I guess it was…and I always wondered what was the magic of the 21 db. And I tried to track that down. And I found what you have done here – if you look at only the noise, you come up 4.3 dB. If you look at the noise and the intermod, you end up with twice that.
BRIDGETT: No, actually I have since worked that out in greater detail. And it depends on the type of distortion that you’re talking about. The 4.3 which has the highest technical distortion – highest ordinary distortion and if you come all the way down to second level distortion, it’s 13 db. And if it’s limited to third order distortion, that is what Ken Simon was working on, it is the 8.69 dB.
TAYLOR: You know John Walsonavich, I guess, Service Electric, over in Allentown, Pennsylvania – Mahanoy City. John was a real character. He had been a hard rock coalminer. At the time Pennsylvania Power & Light was forced by some government action to divest of its appliance business. And John talked to them and asked if they would let him take appliance stuff on consignment and that’s what made Service Electric. He built it up into a big business and he was really very capable of turning things into money – which is a good thing. I went up to Allentown one time because he wanted a report on a technical review of his system for the bank – so he could get some money from them. And we measured the distortion at the end of the line and about 50 some amplifiers deep it was really in very good shape – and hard to believe. So I looked at some of his amplifiers and they were on a Lafayette Radio aluminum chassis and all the parts were right out of Lafayette Radio and he built his own amplifiers there in Mahanoy City. I took one of them back to our shop and did some measuring on them, and discover why he could have 54 amplifiers and still have relatively good noise performance – because his gain was 10 dB! He had his amplifiers at 10 dB. Of course he had a lot of them, but still …
BRIDGETT: He knew what he was doing.
TAYLOR: I don’t think he knew what he was doing, I think it just worked out this way. But it was the one time I’ve seen anything close to the Naperian gain and it really worked out. Even with crude home built stuff, it couldn’t have cost him more than $100 on the outside. It worked fine – it looked terrible.
BRIDGETT: He didn’t try and get the biggest bang for the buck.
TAYLOR: You got it. He did all right but I never did get a real answer as to why 21 db gain, but I think it probably was where it was convenient to come out.
BRIDGETT: You know the funny thing is when I broke that paper, the fact is we had 20 db roughly gain in the 212. And they were talking about 40 db, 50 db gain in the competition and I knew that much less gain I thought was – what I was going to prove was that as you get less and less gain – distributed gain – down to 0 dB per block would be the ideal. I was surprised to come out at 4.3 dB. I really was. I just thought that a distributed gain, distributed along, that it was going to be the answer.
TAYLOR: I’m not sure yet that there was really a rationale for 21, 22 db except that I think that’s the way it worked out.
BRIDGETT: Of course actually, I think the final answer really is that – if you want the least distortion and best noise, you get 4 plus 13, depending on what type of distortion is the best. But the final thing is that you take as much as you can stand and watch economics.
TAYLOR: But now they’re using amplifiers that are 26, 27, 28. A few of them are around 30, even 33 db. But they’re used in limited applications.
BRIDGETT: And you know the big thing is, everybody is forgetting now with fiber optics – the same limits will apply, eventually, if you start cascading enough of them…
TAYLOR: The thing that a lot of people may have not have realized at first, until I began doing the arithmetic on it, the 10 mile fiber thing you put in, is equivalent to about 6 or 8 or 10 amplifiers in distortion and noise…and so you have not really improved matters as much as you think you have.
BRIDGETT: That’s right.
TAYLOR: I just will not allow anybody, if I had anything to do with it, to cascade fiber links. It’s bad enough as it is.
BRIDGETT: But you see, what you’ve got to do is to start figuring just what is the equivalent now. Everybody is saying “oh, you heard it’s unlimited”. It isn’t really.
TAYLOR: No, it’s not unlimited – by a long shot. When you go digital, I mean we are about there…
BRIDGETT: If you go so far that you can go along with where you have to start the figure, but you are still going to have to start the figure.
TAYLOR: Yes. But then the thing about it is that you can regenerate it – not perfectly, but you can come pretty close.
BRIDGETT: But each time you regenerate even one more amplifier, you lose a little and you have to stop – there is a difference in figuring. It’s like AM and FM, because the noise floor, noise limit on FM as against AM, you have to take a new account at some point, and the difference is bigger with digital than with FM. If you start forgetting it, it will come up and bite you one of these days.
TAYLOR: Do you have any opinions on the compression business that we are getting into – do you follow me – digital compression?
BRIDGETT: Oh, digital compression. I’m not sure what methods we use – they are methods – and I have not followed what they use now. I would like to see what they use now. They’re are methods, and some of the compression ones are going to start cutting down on your range.
TAYLOR: There seem to be two things that are done. One is to eliminate or minimize the amount of redundant information. For talking heads, there is an awful lot in every frame that is redundant – frame after frame after frame. So you cut all that out and that is one way. Then the other way, is in the modulation – because you can’t use digital base band – you have to use modulation – so your now using quadrature modulation, 16 quad and as many as 64 quad. Now you’re getting into some pretty complex modulation functions that you can get a lot of bits per megahertz – bits per hertz. So the combination makes it possible to put a whole lot of information into a 6 MHz channel.
BRIDGETT: But again, any of those things are beginning to narrow down what you can do.
TAYLOR: So far they have not been really tested in the field and that is one of the big questions I have in my mind. They do beautifully in the laboratory – the demos are great – they have a problem with motion, because any fast motion artifacts begin to show up.
BRIDGETT: That’s the real thing you have to watch for. You want to watch how many of these things are essentially adding delay. You can always say that one of the first things they do is use delta modulation. What you do is you send real slow scan and only make a change when the change occurs. All right, but that ends up, if something does happen quick, it slows you down.
TAYLOR: And then when you are deleting information from a picture – in the laboratory you can do that and people look at it and gee, you can’t tell the difference. But somebody sits in their living room night after night after night after night looking at that picture; after awhile some of these things happen over, over, over again, and even though they are mild, they begin to be annoying. So I think there are a lot of questions you have. I think it will work.
BRIDGETT: It’s like I used to tell George on this – that you let something happen on your system too often and then the customer starts seeing it happen, and then you’re in trouble.
TAYLOR: Another little thing I dreamed up in my mind – I think I talked to Don Spencer about this one time, but cable television doesn’t really have to be good it just has to be better – better than anything else that you can see, and better than it was yesterday – it doesn’t have to be good, it has to be better.
BRIDGETT: That’s the big thing – how much noise can you afford, how much distortion can you afford. It doesn’t have to be too good – but it has to be better than what the customer is used to seeing. If you have one seen a given level of distortion, you will see it every time it happens.
TAYLOR: And the thing that’s happening now is that the TV sets are getting larger and larger and as you say closer and closer in terms of picture heights so they are just getting more critical. Sets are getting better and it’s no question that they getting much more stable.
BRIDGETT: The thing is that it took George a long time to see what engineers, like me, were doing when we looked at pictures. The first system we went to like that was Zanesville, Ohio. And we all went to the headend and made a list of all the imperfections coming out of the headend – “what are you doing?” We’re looking at how bad the pictures are here. We’ll compare, and see how good they are at the end of the lines. What we are looking at is how good is the system – what is the system adding to it. But still his idea was that he wanted perfect pictures – just like all of them – like Nick Sanguinetti. He was really wild. He had no technical ability at all. The only thing that would satisfy him was an A/B switch.
TAYLOR: He was not technical?
BRIDGETT: Nick Sanguinetti, not technical at all. He was in the granite business. I don’t know whether he actually dug granite out of the ground or what.
TAYLOR: Ray Wilmotte was – I guess he still is alive, a consulting engineer – a broadcast engineer, back in the forties and I got to talking with him – he’s been a consultant to the FCC for the last 15 years maybe. He’s getting quite feeble now, he has eye problems, maybe he’s through with the FCC – but they assigned him the task of – this is long before HDTV came along – assigned him the task of figuring out how do you define a good picture. And he went at it in great depth and told me a story one time…he was with an artist and there was a picture on the wall – I don’t know if it was in a museum or not – and he asked the artist “how do you judge the quality of that picture? Whether it’s good or bad or all right or what?” And he said the guy turned around and walked away from it and then started looking at it. Ray said, “I’m an engineer – I would have walked up to it and begun to look at it in detail. This artist walked away, so you could get the overall perspective. It’s an interesting thought. Well, I think we have patched up this tape a bit. I’m learning lessons about recording. You have to push the record button down! What have we here? We’ve got … this is yours … and you gave me a copy of that … and this one you would like a copy …
BRIDGETT: And I don’t think I need too many of those other things.
TAYLOR: Does this belong to something?
BRIDGETT: This is a list of some of the – I don’t know what – who or what some of these various products we have there …
TAYLOR: 209…what was 209? Is that an early amplifier?
BRIDGETT: I think it was one of the amplifiers – I don’t know – maybe it is in this list, because this had most of the stuff I think in it and sheets on it.
TAYLOR: This one is called chain amplifier . There was a whole series of them.
BRIDGETT: Oh yes. There was a lot of them, for different purposes too. This one …
TAYLOR: These charts are at Soldier’s Field.
BRIDGETT: Yes. And these are later – these are not very early ones – although they are more complete – I think that’s the pulse amplifier there. It shows some pictures of pulses generating .
TAYLOR: You still did some government work and laboratory work after you got into cable.
BRIDGETT: Yes I believe we did. The cable began to take up most of our time. The tail began to wag the dog.
TAYLOR: This Collins and Williams material – would you like that back?
BRIDGETT: I would like that back, because I worked with those people quite a lot and I’m trying to … and of course, they’re no longer alive.
TAYLOR: Collins and Williams – Collins – is one of the first … is that David’s Collins?
BRIDGETT: Chuck Collins, yes.
TAYLOR: They came up with, no another guy, David Carson – at Bell Labs, came up with a figure of merit for cable amplifiers. And I studied it and finally got where I understood it and I showed it to…oh, I know, I used it in a hearing in Tulsa – a franchise hearing – we used the analysis. And Gay Rogness, do you remember Gay Rogness who was at Anaconda. He was a very nice and smart guy and I lost track of him – but he was so impressed with that – he gave me all the credit for it – I didn’t deserve it because it came from Bell Labs. He thought that was just great.
BRIDGETT: And you might find that interesting for the museum. A little bit of the history of cable in New England.
TAYLOR: I’ll tell you another little story – I was the secretary/treasurer of the Montana State Association. And I got a letter from Joe Sample one time. Joe had a TV broadcast station over in Billings. I have forgotten why he wrote to me – but he started the letter out “I really can’t call you fellows’ thieves, because thieves work stealthily at night and you guys work right out in the open stealing programs! I just ran across a whole … 6 boxes full of old files … and I have been hunting for that letter from Joe Sample and I bet I’ll find it in some of those files.
BRIDGETT: This is the thing I’ve always not been able to understand…
Woman’s voice: Is that still on?
BRIDGETT: Yes, but I’m ready to turn that off now.
End of Tape 1, Side B
TAYLOR: Okay. Now we’re back on the air.
BRIDGETT: We had the … the 427 we sold, as just this thing here. In fact, I sent a bunch of those to the museum, just the way they were shipped, with the instruction sheet for connecting them. Now the 427 was just this piece here, which split two ways and a 150 ohm resistor. Then what we did was we had a 432 model that had two of these in a four way. So we had in a little box 4 outlets here and 1 in and what that amount was 2 two ways split into 2 two ways. So we had a four way tap. That lost you 6 dB each way. That was the only disadvantage of that. You had to try to space where these went so you didn’t put too many in at one point. (See SKETCH)
TAYLOR: This was — what? 3 quarter wave length at the middle of the…
BRIDGETT: No. This was a quarter wave at low band.
TAYLOR: Quarter wave. And three quarter at the high.
BRIDGETT: So, when we got to fill in the mid band, you couldn’t use those, but by that time we had a better tap. But that’s what we used at first and what we would try to do here was avoid too much of this splitting loss in the early stages. We had several of these: five ways, four ways and then these were the two ways. And if you could go far enough and then maybe come back, you come out here you’d come to your first three way split that would then go into four ways and then you’d also split and come back to go over there, so you could get things to…
TAYLOR: A little clumsy.
BRIDGETT: A little clumsy, but people do that nowadays…
TAYLOR: Oh yeah. There are other reasons for doing it too. I’ll tell you a funny thing about this. This is the one that was in a flat box about like so, with a flange around the side and had a plate that would come with a little thin rubber gasket. Oh, it must have been 5, 6 or 7 years ago. Leakage became a problem and the first horror story came out of Harrisburg, PA. You probably heard about that one. But the second one was out of Flint, MI and this was a plane flying about 35,000 feet or 25,000 feet that got a severe case of interference flying over Flint. Well, Comcast got severely reprimanded because they didn’t really comply with all the requests anyway, and they paid a maximum fine of $20,000. But Dan Aaron called me in and asked me to go up and look at Flint and see what the situation was. Well it turned out that the problem was that Michigan Bell had built the system in the city of Flint itself…
BRIDGETT: I remember.
TAYLOR: … using SKL gear, but the design was a nightmare. The trunks just wound all around everywhere and they had a lot of these taps in and you’d look at them and open them up and gee, there was nothing to prevent leakage from coming out of those taps, just absolutely wide open to leakage. But the system that was built later by Comcast, outside of Flint, was…I guess it had a few problems but not too bad. It wouldn’t have been the major leakage problem like the one that Michigan Bell built was. That was a funny thing, but it turned out that those SKL taps were one of the big sources of leakage. Nobody thought about leakage at that time.
BRIDGETT: No. Well, in fact, we had to start thinking about leakage right away when we first put these things out. See, what you did with this, you just soldered here, center conductor to this outside to these pigtails, and here you had two pigtails and so you soldered ground to the pigtail, and sent the center conductor to this one here.
TAYLOR: I see. So you didn’t have any connectors on the thing.
BRIDGETT: We had no connectors. But of course if you didn’t keep those awfully damn short, you had leakage too. And so what we finally did, we came up with a little copper cup just about that size that after making up one of these things, you just put enough on there to make sure you weren’t going to ground it out; tape or something. And then, cover it over and solder these two pigtails. (Sees sketch) Those things without that would leak quite a lot in the early days and this was long before anybody was measuring…
TAYLOR: Oh, yeah. Leakage wasn’t a problem.
BRIDGETT: Well, we had some problem with leakage in the early days, like cases where, up in Barre for example. You see Barre was a town where most houses were close to the street in those places. People would be aiming their antennas at the cable system to get a signal and then they’d complain about interference. So that would be fine; they’d go up and clean up all the interference and you don’t get any picture at all. [Laugh]
TAYLOR: We were leaking so bad up in Kalispell, we found people would steal the picture by taking a piece of twin lead and stripping it back and wrapping the wires around the telephone drop line. There was so much leakage to the telephone wires that you’d get the picture that way. We had to make some changes.
BRIDGETT: Well, as you can see, we started in with the problems with leakage pretty early with the paper you see there.
TAYLOR: I see the effectiveness. One of the stories that I’ve heard. Did you know Joe Hale?
BRIDGETT: Well, the name sounds familiar.
TAYLOR: Well he was up in South San Francisco, right under Mt. San Bruno, which had two high power VHF stations, full power. They were low band. At any rate, he could not keep his system tight. He said he’d go through and tighten it up and two weeks later, it was leaking again. Of course, it was a terrible situation. One day the AMP connector manufacturer was in and they had this big compress machine that would compress the hexagon ferule down tight onto the cable, so you had a good tight bond. But, with all that pressure they were putting on it, they had to put something under it, because the aluminum was too soft, so they had this little sleeve that they’d put in.
BRIDGETT: A steel sleeve?
TAYLOR: Yeah, a steel sleeve. Well, Joe said, “Boy, that’s just what I need”, and he bought a whole bunch of those sleeves and went out and put them in and he was able to keep it tight after that. He told Jerrold about it. Jerrold then put out a sleeve connector, or a sleeve for a connector. The problem then was that the contractors who were installing didn’t like to have to core out the cable. All that work, and nobody was ever going to be able to tell whether they had sleeves in or not. So they just didn’t put them in. That was when Eric Winston of Jerrold came up with the integral sleeve. Of course, that’s standard now, everybody’s got it.
BRIDGETT: That was always the problem. Being able to catch the contractors. It’s like up in Woburn. We ran a run from a headend back to the office. It was the other way; it was the office to the headend. But, the fact is we also ran something off air and so by checking the delay from the off-air to the. We were able to say go tighten up that connector of such and such an amplifier and get rid of it. From then on they didn’t try to get away with things.
TAYLOR: Cute. I’ve never heard of that. That’s a cute idea. Another thing we had in Kalispell is that people were picking up the 15 KHz incidental radiation from sets and so they were getting this whistle in their radio sets when they were trying to listen to anything. I don’t know that we ever did anything about that. There wasn’t a lot we could do about it.
BRIDGETT: The whole thing is kind of funny. You see now, we never, at any of the systems I really had anything to do with directly, we never worried about the off-air pickup. Figure that’s up to us to solve. And I always took that stand, that it’s up to us to solve it. Some of the political situations would get you. I went up to Corpus Christie where they had a lot of very strong off-air stuff. The guys were doing a good job trying to keep it down. But I did recommend to them, it was only time I ever did, that they request…
TAYLOR: Are you talking about interfering with off-air reception?
BRIDGETT: No, direct pickup. I did suggest they request the FCC to grant them a right to put these channels on another channel. And I suggested they keep one on-channel as a help to them in locating the problem. And another time, I forget where it was, I wrote a little report, the local engineer for the station made a real nasty thing about cable trying to interfere with them and all this kind of thing. So I wrote a long report after having made all these detailed measurements and so on, and I had concluded that the interference they were receiving is from station KTXY, whatever and stopped there for a moment and apparently went off on something else before I got back to explaining why, and I knew that that guy was going to be steamed as he read it. But it sure was direct pickup from that I went and explained that this doesn’t mean that the station is being run wrong and so on, it’s just one of those things that can happen.
TAYLOR: There were some funny things with broadcaster. I remember there was some difficulty and I can’t remember what it was. Up in Kalispell, we picked up this Spokane station about 150 miles away on a 7000 ft. mountain. It still wasn’t line of sight but we could get a good signal. And then we microwaved from there down into town. But something happened on channel 4, the station in Spokane. The picture was poor and we called over there and complained and they didn’t have any problems, it’s our problem. It went along for several days and all of a sudden it cleared up. So I told my guy up there, I said, “Give him a call and tell him that it’s been fixed”. Well he did and the guy said “Well I’m glad you found your problem.” And we hadn’t done a thing. Glad you found your problem.
BRIDGETT: Well, one of the interesting things that happened up in Maine, it was a complicated thing, and there were some nasty feelings all around, I don’t remember all the details, but Owen Hanigan was in on it. The, I forget which station it was, but anyway, one of the stations was a must carry thing and they were picking it up on a chewing gum and rubber band microwave and the pictures were pretty terrible lots of times. I did find out a way of proving something that I didn’t try to prove, just hinted enough at it. He was not getting his pictures the way he said he was either. He was picking up directly off Mt. Washington.
TAYLOR: Uh, Oh.
BRIDGETT: Which is the one we were carrying in its place there. But, Vince Parker, I think that was his name, a guy who at that station, he was kind of a little Hitler up there. He was that kind of person a lot of people didn’t like, but he had pulled a little fast one too. He had taken out some of the vertical interval signals and put his own call letters in it.
TAYLOR: Uh, Oh.
BRIDGETT: So, we could tell every time this guy was taking a direct signal. I forgot how we let him know that we had the goods on him if we ever wanted him to. I think we sent him a picture showing him the vertical interval, because it rolled up or something, showing what kind of pictures they were getting.
TAYLOR: The battles of the broadcasters are not nearly as severe as they used to be. There are still some of them there.
BRIDGETT: There really was no need for them to be.
TAYLOR: What do you think about the future of Cable Television? Where do you think it’s going? What it ought to do?
BRIDGETT: Well, the fact is up until we got into the fiber optics thing, the thing is I figured what we had to do is keep making better amplifiers to where we could run cable across the country without any bad degradation and run a short system on the end of it. Of course, we can do that now.
TAYLOR: Well, of course satellites take care of that anyway.
BRIDGETT: Well, but again, the satellite things are not really the answer. Satellites have the same problems as broadcasters. There is only room for so many.
BRIDGETT: But, you see now with the fiber optics, you can run as many as you need.
TAYLOR: I was disappointed in a way when Jim Chiddix and people at ATC came out with the AM fiber, because I thought, gee, all the problems we’ve got with analog AM, you’re just buying the same things. But, I soon came to realize that it was a necessary situation because of the TV sets. You couldn’t afford the conversion is homes.
BRIDGETT: Yeah. Well, but again. We now have gotten to where something, we can do it with cable, pretty much on AM. But, now for the long distance stuff there is no question we should go digital.
TAYLOR: Oh! That’s right. No. FM is out. It is either AM or digital. AM when you have to match a TV set and digital when you are going to do anything else.
BRIDGETT: The facts is the way were are going now, it’s just go to different hubs and you don’t need too many places where you convert from digital to analog and so you now cover everything you need without … I think this is the way. I did notice that … I attended last year’s technicians meeting here in San Diego, where they had the fiber optics thing and I noticed a couple of places that just decided in the beginning to go digital. Because the thing is once you pick your signal to noise ratio, you’ve got it, no matter how far you go.
TAYLOR: The most remarkable thing to me is that the fight over HDTV got started and, what was it, 1988, in Dubrovnik, Yugoslavia, where the U.S. tried to push the Japanese MUSE system on the world, and the world wasn’t buying. The guy at CBS, Joe Flaherty, came back very much disappointed. But they kept on pushing and the FCC took up standards and 4 or 5 systems were proposed, I guess 6, all of them analog, but various modifications of how to get high definition, and how to deal with the 6 MHz channel limit. Along comes Jerrold with its digicipher, totally digital, aggressive compression, much more compression than anybody had ever really, well I won’t say anybody because Compression Labs and some of the other people knew you could do it, just turned the HDTV thing upside down and the Japanese MUSE is now obsolete.
BRIDGETT: Oh! I remember one thing now that nobody every followed up on. I remember way back in the early years, Lester sent me down somewhere in Pennsylvania where, I think it was one of Diambra’s systems. He started out with a Jerrold 3 channel system and he wanted to carry more channels. So, he started with kind of a split channel arrangement. He’d take the low end of channel 3 on one band amplifier and the high end of 3 on the channel 4 amplifier.
TAYLOR: Oh, really?
BRIDGETT: And, what you got, cause you just lost a lot of the information. But, as a matter of fact, it was very interesting thing, I don’t know whether you remember years ago what photographers would tend to do, give you soft pictures with a lot of detail and this what you tended to get there. You have enough detail in there and then of course scanning the other way, you didn’t lose anything.
BRIDGETT: And I’ve often thought that there would be tricks like that you could pull to improve the amount of usable information, not real information always, but when I came back there and saw, I thought “Oh, this guy isn’t going have anything, but when I saw what he had, it really impressed me what you could do with some of these things.
TAYLOR: Of course now, they are putting in 150 channels in Queens, Brooklyn, NY and a Vice President of IEEE, said “We’re going to have 2000 channels and its coming by satellite and it will wipe out cable television and broadcast, both of them will be gone” and I said, “Well, but there’s some problems with satellite because you got to be able to see the satellite, you got obstacles terrain and so on in the way. Oh, well we are going to be using the polar orbit, low earth orbit thing. And, well I wrote a column, I think it’s the one that will be published in May, and the title was “Get Real”. And I talked about the scheme. It’s very tough to say that something isn’t going to work, in fact, you know it will work, it can be made to work but when you start figuring out whose going to pay for it and who wants it enough to pay for it, then you are talking about marketing, and now you are talking about something different from whether you can do it or not.
BRIDGETT: Well, the thing is one thing cable did prove, very fast, was this myth of 3 channels is all you can carry. There’s no market for it.
TAYLOR: I got trapped in some of that myself when they first came up with the 400 MHz thing. 35 channels seemed like an… Few places like the San Francisco Bay area, maybe a couple of other places where there were enough stations scattered around that there was enough off-air stuff and you add some satellite stuff to it, you can see that 35 was going to be a limitation, but boy real fast was a serious limitation.
BRIDGETT: All it took really to prove that was Ted Turner and WGN and I think there was one other one.
TAYLOR: WGN incidentally is Roy Bliss, Jr., the son of Roy Bliss, who is up in Wyoming. Did you know Roy?
BRIDGETT: No, I didn’t.
TAYLOR: Roy, I got to know him fairly well. The son I know simply because of the father, but we talked. But Roy Sr., was the guy whose system was involved in that microwave case, Cloud Peak. He’s out of the business now. But I was talking to Roy Jr. one time and asked about his father, and he said “Well, dad had a very serious accident.” At his age, he was riding a motorcycle and had an accident and broke some limbs that were in pretty bad shape, but last time I talked to Roy Jr., he said his dad was getting along fine. I don’t know, when a guy in his 60’s goes out motor cycling, he ought to have his head examined.
BRIDGETT: Well, I want to get my flying license back soon as I get this eye back in shape.
TAYLOR: Earl Hickman, you know of course, his real love is flying. He got into cable and electronics kind of as a hobby and was an accident. I visit him. He’s in the airport up here in … what’s it called?
BRIDGETT: Is that Gillespie?
TAYLOR: Yeah! Gillespie. He’s got two hanger condominiums there, two big hangers. When I was there yesterday, he had 5 airplanes in there. Four of them he had practically built from scratch by remodeling.
[Taped turned off]
BRIDGETT: … which energy was transferred the coupled electric fields and a coupled magnetic field. But you see here, it really didn’t matter which way, you could always tie it down to the size of the wave inside and the wave outside. This is where the interesting thing comes, if I’d looked further at this at the time, I’d have seen how to handle the different way to inject it. You notice that we have two waves, two coupled lines, but in this case one was inside the other, but with two coupled lines you have a wave both ways and that gives you a directional effect. All you have to do is separate the … and you got a directional coupler. You know sometimes you don’t see that while you’re doing it.
Note: We were looking at a paper entitled “Proposed Method for Measuring the Shielding Effectiveness of Coaxial Cable.” July 9, 1954, by A.W. BRIDGETT: and L.C. Smith.
TAYLOR: That’s right.
BRIDGETT: You look at it a few years later, you see.
TAYLOR: Well, there it was.
BRIDGETT: But, this one, I helped pass this around the industry a few times when everyone was looking at how to measure … In fact this is the actual structure; this is very similar to the one that Beldon came up with.
TAYLOR: Okay. The seed?
TAYLOR: Now, Ken’s comment about the seed was that it will give you relative shielding effectiveness, but it wouldn’t give you an absolute measure.
BRIDGETT: Well, you see, I came up with an equation that was exactly the transfer impedance.
TAYLOR: Using the measurements from this instrument?
BRIDGETT: Yes. You see there we have magnitude of transfer impedance, you see, these are the two velocities and so on and then the actual measurements and then [Zo] is the impedance of one cable and actually, it worked.
TAYLOR: Now, do you have copies of this?
BRIDGETT: That’s the only copy I have left.
TAYLOR: Okay. I’ll make copies and ship it back to you.
BRIDGETT: Now, there may be a copy of that at the museum too, I don’t know. A lot of these things, if I have more than one … Oh, I want to give you something else that you can take too. I didn’t turn it over to the museum because I didn’t think anyone would know what it was, so you refer to it in your notes. So I have a brand spanking new copy of my co-channel filter. That I couldn’t throw away. It was just too nice looking. Okay. Now this is a thing that we did a long time ago.
TAYLOR: I’m looking at a paper entitled “Is Snow Added by the Amplifiers of a Community Antenna System” by A.W. BRIDGETT: and this was presented by the National Community Television Association Convention, June 14, 15, 16, 1954.
BRIDGETT: That was where we proved that there is an optimum gain. The more dB for the buck was the wrong way to go. It was the first time we did that. I took the simplest case there. Kim Simon shortly thereafter took that into a case where the limiting case was third order. I have since done some work covering all orders. And the interesting thing is this one takes you in the limiting case of very high orders.
TAYLOR: Oh, I see.
BRIDGETT: But this one I took was very simple. It was a brick wall distortion case where you keep below a certain level and you don’t worry…
TAYLOR: The optimum gain comes out to be what?
BRIDGETT: That was 4.3 dB.
TAYLOR: 4.3? Really.
BRIDGETT: Now, Ken’s, he had third order. You see the difference is on this… I do know, I presented this to the people down at Bell Labs and they wanted to know what happens if you don’t have this brick wall situation. Well, the fact is if you take… Well what I did here assumed that if you stay below a certain level, you have no distortion. If you go above it you get unusable distortion, maybe only a little but definitely around there. With that type of distortion you come up 4.3dB rating. With a third order where it comes up at this slope and therefore as you go along you got to reduce the opposite slope, that comes out to 8.6. Second order, if that is the limiting case, that slope this way, it comes out 13. But the interesting thing is if you go up to higher orders, 3rd, 4th, 5th, and 6th and so on, it approaches a 4.3.
BRIDGETT: I haven’t really written up papers, and I’ve done the calculation for my own benefit, but maybe I should sit down and do some of it, just before I’m all gone. But this thing was presented … The fact is we were selling roughly 20 dB amplifiers with Jerrold selling 50 dB gain amplifiers.
TAYLOR: Jerrold had 50 dB amplifiers?
BRIDGETT: That’s what they claimed. They never ran them at 50.
TAYLOR: I don’t remember anything like that.
BRIDGETT: The dollars per buck argument tempts people. Hey, look what we’re getting. They did know they couldn’t run them at that in cascade. They kept it down to somewhere around 30 or 40 in practice.
TAYLOR: I never encountered that much. Did you mean Jerrold or RCA?
BRIDGETT: Oh. RCA had 80 as I remembered. In fact, the thing I know about the Laconia system is that they were single channel amplifiers … 80 dB. They couldn’t put 80 dB in one case and make it work. So they had them in two packages, cascaded, 40 and 40. When they built the system, they found they couldn’t run it cascaded, so what they finally did was run them down to 40 dB per amplifier by putting a pad in between those two. So they had 80 dB amplifiers padded down to 40 and they could cascade them a reasonable distance. So they did make them run up in Laconia for a while.
TAYLOR: Al Malin was the guy I was trying to think of. He was in Rochester, NH and I think it may have been Laconia.
BRIDGETT: Well, he might have been. I don’t know. Now the Laconia system was a very interesting thing there. That was part of the property owned by Harmon White’s family. And it was going downhill, badly. So the family apparently voted Harmon in, you’re going to run this. He’s made it pretty… The first time I went up there to do a proof of performance, and all you can say was “Well, that looks like it might be a picture.
TAYLOR: There are some framing bars occasionally, huh.
BRIDGETT: When we got through with that and I showed him what he had wrong with them, with the pictures, and with the system and so on, he started the program and started cleaning it up and his system is really a quite good system. In fact, what he’s done recently, I told him that the last thing I did before I got out of New England was that I thought fiber optics was about ready to do things, so he’s got a lot of fiber optics in there too, and it’s up and running beautifully. He’s got rid of some headends, got things tied together…and of course, he had done some stretching, that you had to keep things running perfectly. He ran from…what was the mountain there? Down south Laconia? He ran all the way…
TAYLOR: Gosh, I should know that too, but I don’t
BRIDGETT: Well, anyway he ran way up to Meredith, one headend finally. Of course, in the beginning, he had little headends all over the place. The first thing I did, I had him buy the best amplifiers, we got in the same the earlier feed-forwards that there awful kluges to maintain. But we got a feed-forward run up there so we could get decent pictures.
TAYLOR: This is fairly recent years then?
BRIDGETT: Fairly recent years, yeah. Well, let’s see, I don’t remember when he first took me on as a consultant for him, but it was like, “What is it?” was all I could think of when I saw it. Well, it’s like, I went up on the mountain, and George was going to meet him and I was going to come down and meet him for lunch. Well, you couldn’t get up the mountain, except by lugging something on your back, so Jerry, his technician, and I had lugged this stuff up and we weren’t about to come down for lunch or anything or …
TAYLOR: I can imagine.
BRIDGETT: George told me that Harmon was all upset. He said, “Socks ought to be down here.” Well George said to Harmon, “Is he charging you by the hour or by the job.” George knew me. I’d given him a price to this job, so I was going to get the job done. He said, “Don’t worry, he isn’t going to give you a higher price. He’ll get the job done.” That was the beginning of getting it up, the whole place upgraded. Okay, let’s see, let’s try to get back on track, huh. Alright, well that’s the directional coupler. I think I’ve given you more detail that you wanted on that.
TAYLOR: Oh, no. That’s fine. What about the solid state?
BRIDGETT: Now, solid state. Don Spencer was fascinating with wanting to get it done and wanting to get in the use of solid state. Now this was something that everybody wanted to do in every place. So, I’ve have been tied up over these same years with an elevator company and they wanted to get into solid state. Luckily…
TAYLOR: Who had been tied up with an elevator company? You had?
BRIDGETT: I had. Delta Elevator. They just sold back out to Otis this last year or so.
TAYLOR: This is while you were at SKL?
BRIDGETT: Oh, yeah. What happened there is that I’d known Paul Abbott who started this back in Jr. High school.
TAYLOR: Oh, I see.
BRIDGETT: He came up with this idea for an arrangement for emergency power to run elevators in tall buildings. He was working for Otis at the time and offered it to them and they didn’t want it so he said “Hey, this is worth doing, I want to do it.” So he went work and he sold one to all the building in town, and then Otis told the building that they wouldn’t maintain the system. So Paul said, “Hell with you”. He gives him a bid to maintain the system. So, we got to where I was just kind of on the back burner as a consultant with them and most of my time was with SKL. No, actually that didn’t really start till I was actually out of SKL, that’s right. I really working partly between Colonial and Delta. Well anyway, we got all the high rise buildings in New England practically. We had Boston all tied up. We had Worcester, Albany, and Providence. But of course, a lot of the solid state that you got, presumably it was designed for power work, but it wasn’t up to it. They cut corners by making chips rectangular and if you had high current densities all crowded into the corners. They burned out. So you couldn’t trust ratings at all. You had to check ratings yourself. We finally did get elevators really running with solid state there. Now at about the same time, much earlier at SKL, Don was very interested in getting in to solid state. His idea was to build the amplifiers right in as a section of the cable, which as we found wasn’t able to be done. And I did do some work on that. That’s one of my background jobs, trying to keep up with solid state, finding if there was anything, and I had worked out a few of the types of specifications we were going to need, if we had them.
TAYLOR: Are you talking now at the late 50s or early 60s.
BRIDGETT: This was in the … I don’t think we found anything that was usable in the 50’s. I think it was in the 60s that we began to get something. I can’t remember the exact time. What happened there anyway, was that Pierre came in, knowing all about transistors, he sold Don Spencer quite a bill of goods for some time.
TAYLOR: Where did he come from?
BRIDGETT: I don’t know where he came from? I know he finally went in to real estate and did quite well.
TAYLOR: What nationality was he?
TAYLOR: Swiss. That’s what I thought.
BRIDGETT: He was a dilettante in electronics and we could see he was going to be chief engineer and so Lester, Win Bemis and I started a little company ourselves. Image Instruments. We did pretty well, but unfortunately, we did go with Lester, who was a marvelous engineer, but no good as a business man, and unfortunately we put him in as president and chief executive officer and he knew how to grab the reins and hang on.
TAYLOR: When did you form Image Instruments.
BRIDGETT: Again, I’m trying to remember the exact date. I’d say that was in the…let’s see, that was probably in the very late 50’s because that was about the time Pierre was obviously going to be chief engineer, and I wasn’t going to work under that clown.
TAYLOR: I see. Then you went back to SKL.
BRIDGETT: When Image Instruments folded, I went back to SKL. That was in the early 60’s. Not too long a period.
TAYLOR: How long did it last? A year or two.
BRIDGETT: Image Instruments?
BRIDGETT: I think a little longer than that. We managed to get a good name built for ourselves, and the quality of our equipment. And some pretty good contracts. If we had done things a little different, I think we could have really been a big outfit. Well, those things happen.
TAYLOR: That right.
BRIDGETT: It’s one of those things that makes life interesting.
TAYLOR: It’s the way the cookies crumble.
BRIDGETT: Yeah. Well, at any rate, that was the story. Now, I don’t know exactly when Pierre left, it was about the time I went back and win Bemis …
TAYLOR: I see. Well, Jake told us about the cylindrical amplifier. Jake was there at that time.
BRIDGETT: Yes, Jake had come back while Pierre was still there.
TAYLOR: I’m not sure he was full time, but he was at least full time. I don’t remember.
BRIDGETT: A lot of people came in interesting ways. Bob Brooks came in as a Northeastern co-operative student and done real well. Jake was studying for his doctorate at MIT at the time when he came. Then he left SKL, not being unhappy with SKL or anything, just that he felt that the government of Israel had paid his way to MIT and he owed them. So he went back. Then they had him in bureaucratic job shuffling papers, so he finally laid the law down and said “I’m either going to do some engineering or I’m getting out of here. So he wrote a letter to Don and came back. Now that was while we were gone. And Pierre was chief engineer then. Now, we did know some of the people, you know, we had little talks with them. We knew things were going bad with SKL. The real key was that we knew that … I mentioned Dick Berwin …
TAYLOR: Dick …
BRIDGETT: Dick Berwin, the guy who had been first in …
TAYLOR: Oh, you did. I don’t know him.
BRIDGETT: He was the engineer was originally going to take over the CATV thing at SKL. He left to go start his own business.
TAYLOR: Oh, I see.
BRIDGETT: But he was consulting in amplifiers in solid state and everything, so what Don did was, very quietly, commission him to design an amplifier.
BRIDGETT: Yes. And we heard that. It was supposed to be quiet, nobody was supposed to know about it, but you hear these things. Well, I realized, Ok, Pierre’s on his way out. But nobody give Dick the key thing he needed and that is maximum allowable gain. They specked out noise figure, distortion, but he managed the best he could, there was a lot of gain on that amplifier. So it went down the drain. And that was just about the time Pierre left and we came back.
TAYLOR: Now, that amplifier was …
BRIDGETT: Never produced.
TAYLOR: Oh, it was never a product.
BRIDGETT: Never a product. Once it was tested they began finding…but if they had just looked at some of the old papers they would have found it couldn’t work.
TAYLOR: Now Jake talked quite a bit about the cylindrical amplifier. And that was Pierre’s.
BRIDGETT: That was Pierre’s. You see what this was unfortunately, Don wanted an amplifier that would just be part of the cable. And Pierre was going to give it to them. And that is all I know about that. I heard that before Pierre was chief engineer and I never heard during that time. The worse of it is it did work.
TAYLOR: When I was up there, I met Pierre. What he was trying to do was to use DC power for the amplifier, power on cable, and he was also using that as the AGC, letting that vary up and down. He was having a problem with getting hum in that AC power and using larger and larger capacitors just to brute force protect it.
BRIDGETT: Oh, yeah. And some of these decoupling capacitors, I have some of those around, great big things in boxes…
TAYLOR: That’s right!
BRIDGETT: With the case half floating, and some were…
TAYLOR: Yes, he had a real problem and they just could never make that work.
BRIDGETT: Of course, a lot of people tried to use DC power for transistorized amplifier problems. There were some who used half wave rectifiers, a lot of things.
TAYLOR: Well, the fear I think was over corrosion, like electrolysis.
BRIDGETT: Well, it was corrosion.
TAYLOR: But, I talked, I don’t know if it was Ken or someone else I’ve talked to felt we could really could have used DC power to advantage if people hadn’t been fearful of it.
BRIDGETT: Well, we might have.
TAYLOR: We haven’t really had all that much corrosion problem.
BRIDGETT: No. And even that could have been handled I think. But, at least that was the thing. I had some of the junk, some of the DC power amplifier stuff. It was well designed mechanically, beautiful looking stuff. But apparently…In the first place, that was done before they had transistors that worked adequately.
TAYLOR: That’s undoubtedly true.
BRIDGETT: That’s the real problem. Because it was just shortly after I came back, and I told you I had been looking for what kind of thing should we look for, just around that time, we saw the transistor we needed. It was an RCA transistor designed for class C-transmitter work, and it worked like a charm. And that’s what we put into that first color burst. And it was something very similar that Ken Simon put into his Starline One.
TAYLOR: Yes. Starline One. He told me that RCA said that they were rated for 5 watt dissipation and he said the fact was their internal memorandum showed that it was only good for 3 1/2 watts. He said they dropped like flies down in the south, they were alright in the north where it didn’t get that hot.
BRIDGETT: You know, an interesting thing about that, you talked about that here, was it a desperation move. No it wasn’t. It was a very interesting thing. Once we found a transistor could work, several of the engineers at SKL were fascinated with the idea. Now we can make good solid state stuff and we were starting to feel around with what circuits we should use and so on. We were trying all kinds of things. I even designed an amplifier, and I’m not sure if it’s the one you’re referring to that was distributed grounded base. Our house, oh my god had about a dozen transistors and a distributed.
End of Tape 2, Side A
TAYLOR: Okay, I think we are recording now.
BRIDGETT: Okay. Well with the feed forward thing, George Ray always wanted to try feed forward and I kept telling that with all of these bandwidths, it’s going to be too hard to control. Well, when he and Bill O’Neil were there in ADS, [ADS stands for amplifier design service] I’d drop in once in a while, they were right near where I lived, you know, fun to drop in with some of the guys. He dragged me over, he had taken two 212’s and a harness and he showed me the first feed forward. And it worked like a charm. And he didn’t have to do anything fancy at all, just took the two amplifiers as they were and ran his harness of hybrids and so on, and he convinced me. The only feed forward on the market before that was at Century was it?
TAYLOR: Yes, they did have a feed forward. Vic Tarbutton.
BRIDGETT: Yes, they had made out of discrete LC delay line sealed up in a case. What George did was he took straight short pieces of coax, he had control over delay time and everything. That’s what made his so easy to come out right. He had one little adjustment, a trimmer capacitor.
TAYLOR: Well, the Century, Tarbutton’s really caused no end of trouble.
BRIDGETT: Unfortunately, the other one that I had Harmon buy first for Laconia. But, it was all that was available at the time, because ADS had them then, but ADS had gone out of business, so I said “Century’s all you got.” But, at any rate that’s what happened with the feed forward.
TAYLOR: Now I want to get straight, in 19, probably 1967, Don Spencer had a number of cable systems out here in California and one of them was at Lafayette and a group of places around Lafayette. He had used Boston Capital as the financing and Boston Capital came to us, Malarkey-TAYLOR: and wanted somebody to help because this thing was not going right. We got a management contract to manage that… they were going to take it away from Don, and it wasn’t working very well, and they want the management under their control. So we had a management contract that we kept until Monty Rifkin came along and Lafayette became the first system that Monty put into ATC. So, we had that management contract and the amplifiers that we used there, to digress a moment, the cable that was in there was Superior Cable but it was corrugated aluminum, outer conductor, and we found places where there was nothing there, nothing but powder inside the jacket.
BRIDGETT: You see, we never got out much to these systems. I don’t know why.
TAYLOR: We had to replace all the cable, that is all that old aluminum cable, but the amplifiers used were a SKL amplifier and it was, I remember distinctly that there were three or four uncontrolled, no gain control, just single amplifiers and then a mop up amplifier that would mop up with a thermal sensor and mop up the gain. And that was in a 260 number series, I don’t remember the exact numbers but it came about the same time that that high output unit came. And it came also just after Pierre left.
BRIDGETT: Yeah. You see at the time there were a lot of things a lot of us didn’t know much about.
TAYLOR: Okay. Well the amplifier there, the so called cylindrical amplifier, also consisted of several amplifiers without any control and then finally a mop amplifier with both gain and slope, I think. And every 3, 4, 5 amplifiers. Well, that amplifier we used in Lafayette and made it work and it was alright but…
BRIDGETT: Well, there were a lot of amplifiers made by everybody that were alright,…
TAYLOR: We never did complete because Monty came in, bought the system and then we were out of it, but I’ve been trying to get straight about that amplifier. Now the color burst…
BRIDGETT: Now the color burst was an entirely different thing.
TAYLOR: That right.
BRIDGETT: That came in with several things into what we … In engineering, we hated the idea we might have to do a color burst. Once we got going, we were enthusiastic. It’s like we …
TAYLOR: Now, what was it you hated, the fact that it was a module?
BRIDGETT: No, because we had our own ideas what we wanted to do then we found some transistors that we felt were capable of doing this thing and we wanted to get the bit in our teeth and run. Well, what happened was Ken Simon had done a tour de force. It was a beautiful site.
TAYLOR: The Starline One.
BRIDGETT: Yes, the Starline One. It had some real serious problems and we dug them out, but what happened was, anyway, management decided well look, we have to compete with this. They’ve got Western Union approval on this…
TAYLOR: Western Electric?
BRIDGETT: Yes, Western Electric approval, they didn’t really, but they had built it with the idea of getting that and had convinced themselves they had gotten it and everybody else, so we got to get this on the market or something to compete with it. So the agreement between engineering and everybody else was production will take this and copy it and you guys can go off on your own. Very quickly we found that can’t work. It’s like production comes in, and says what is it?
BRIDGETT: And we didn’t even know except this was the future of Jerrold and maybe the thing that saved us. So we had to get to work and look it over carefully. Well I went through everything, and you know what I said, after having done a complete analysis of that damn thing, “It’s a marvelous idea. I would have never have dared to do that.” Complete negative feedback over that bandwidth. It turned out only Ken Simon would have dared to do it.
TAYLOR: Yeah. Yeah.
BRIDGETT: But, that was the real thing that impressed me. He had that in such beautiful shape. Then I did know, but not enough attention was paid to thermal problems in this.
TAYLOR: Which Ken knew very well. He figured it out.
BRIDGETT: Well, that was the thing. We’re not going to copy this or we’re going to fall on our faces. Even if we assumed the RCA specs on them, I said “those things are going to die like flies on every north/south street down in Texas in July.”
TAYLOR: Which they did.
BRIDGETT: Yes. As soon as the afternoon sun hits the side of the case. So that was the first thing we did. We thought, well, the circuitry, there’s nothing to be ashamed of copying that. That’s beautiful, but we’ve got to see if we can get rid of this bloody heat. Everything was done by air transfer. And there was no way we could make any big changes because they had already started making the cases for us. This was going to be a crash job. So I had to try to space things down, make spaces smaller, surfaces wider, to carry heat across the airspace, and we finally released something that we figured, well it’s barely going to live, but we’ll have to put more time on it later. So we did that, then there was another thing. As I said, we had a lot of fun with it. And, that was the year that the Convention was down in Miami (1966) and they had that big gold man. Do you remember? So we stole Jerrold’s gold man and he ended up in the pond, remember?
TAYLOR: I didn’t know about that.
BRIDGETT: We think we know who did it. But nobody would swear to it. But anyway, we had a ball because we thought we had a real good product. George Green had brought in a bunch of real fine salesmen. They weren’t you know, just boiler room type guys, they wanted to work with us and wanted to learn what was good about the product. It was a fabulous thing. That’s the only good thing I think that I could ever say about George Greene.
TAYLOR: I was going ask.
BRIDGETT: But he did. He bought in a fine bunch of salesmen. And if George Greene could have been left out of it, that could have been the turning point at SKL, I think. Because we had a good sales organization, we had a happy engineering organization.
TAYLOR: When did George come in? Can you time that?
BRIDGETT: Oh. Let’s see. That would be the year previous to the Miami Convention. I can’t remember that one.
TAYLOR: I remember being there, but I can’t at the moment identify a date. Okay, the year previous to that.
BRIDGETT: I would guess…He’d been there about a year, I think at the time of the convention.
TAYLOR: And was this before the color burst amplifier.
BRIDGETT: I think he came at just about the time we were starting the color burst program.
TAYLOR: Okay, that’s my recollection. Because I had always thought…
BRIDGETT: The interesting thing is I had gotten to be chief engineer for a while. Jake and I alternated chief engineer frequently and it’s like, when I came back, Jake was chief engineer, but he had left, and Don asked would you mind working under Jake, and I said “Why should I, he’s worked under me.” And we always got along fine together. Oh, but the thing is really, I had an awful time keeping George Green’s fingers out of engineering. He was the only fly in the ointment that could get the engineers upset, because they were happy doing something they could see was good and working, and I didn’t mind the sales department. They could walk in engineering and ask any kind of questions they wanted because they wanted the kind of answers that could help them to sell. It was a very fascinating time. But that was the story. In one sense, you could say it was an act of desperation, on the other hand, it wasn’t quite that.
TAYLOR: You see the appearance that I had as an outsider was that George came in, when you knew that SKL was having trouble. And George as the fixer, trying to pull things up out of trouble, then suddenly comes out this amplifier, which on its surface, looks like a copy of Starline One. That just looks like a desperation move.
BRIDGETT: Oh, I didn’t tell you about the fun we had. Now see, their pilot, they had this great big cavity tuner and you didn’t need cavity shops, it was a gimmick, and it sold too, but we had our filter through our pilots, small little things, so here’s all this space down here, what are we going to do with that. Well, we kind of figured, we had started calling this big thing that had the two balls in it the Scrotum, with the Jerrold amplifier that’s a scrotum. So what we did, we figured, what we’ll do is put a firm ridge right there under the scrotum and if anybody tried to plug a Jerrold amplifier into a color burst case, it’s going to hurt. You can see the kind of attitude we had in engineering at that time.
TAYLOR: Yeah. Yeah.
BRIDGETT: We weren’t in any desperation move, we were going great. But, at any rate, for some reason we didn’t quite make it. We should have made that. Then there was a another time I thought we were going to make it if we went further on it. I would say off hand that was one of our greater successes, pulling of that color burst and making it what we wanted, a better amplifier than the Starline. Because no question, it was. And they had to do some things about Starline I’m sure.
TAYLOR: Well, that’s why they came out with the Starline 20.
BRIDGETT: Yeah. Right. Again that was the…selectivity(?) was a beautiful design.
TAYLOR: One of the amplifiers, I can’t remember now whether it was the 7000 color burst used, actually I think it was one we used in Lafayette, used the photocell and lamp.
BRIDGETT: Now that was a good idea, except it was a better idea traced in the background. You see, we didn’t want to use ordinary diodes or anything because if you’re using a non linearity to control gain, you’re adding non linearity. And so the photodiode was a straight linear resistance that was modified by a separate port, a light, and it worked with no distortion caused by that at all.
TAYLOR: Now is that in the color burst?
BRIDGETT: I believe we got that in a color burst first, yes. But we did…Jake and I sat down and did some figuring. When we did this we thought “now what a minute, let’s look at these pin diodes”, we still have…they’re not ordinary diodes but with two separate modes of operation here, we got essentially the same thing here as the …
TAYLOR: As the lamp, the photo.
BRIDGETT: Yeah, the lamp. We’ve got a straight resistance that’s only effected by this other pair of terminals, and so the pin diode was just as good.
TAYLOR: I’ll bet you that the photo device was in that one we used in Lafayette…
BRIDGETT: It might have been.
TAYLOR: Which I called the 260 series, but I don’t clear that up.
BRIDGETT: I don’t remember that.
TAYLOR: Was Jake there during the period that you left?
BRIDGETT: He was there part of the time. See, he left to go back to Israel before we left, and then I heard he had been thinking of coming back, but he still had questions whether he should or not. But, he had come back before we got back, before I got back. He was chief engineer when I got back.
TAYLOR: In my outsider’s way, I kind of credited him with that photo device for the AGC. But I don’t know whether it was nor not.
BRIDGETT: Well, both he and I, I don’t know which one, we were batting around how we could get something where the control element did not affect the linearity of the controlled element. And that photodiode was one of the ones we came up with between us. But, I think that it was probably Jake convinced me that the pin diode, working in two separate modes, would do just as good…
TAYLOR: Would do the job.
BRIDGETT: Or could be just as good, and so we got a hold of some photodiodes and started checking them and of course, we threw the photodiode away as fast as we got pin diodes. Now, I don’t think it was good that they became a system operator. What little I ever knew of their system operations weren’t up to what some of the help we’ve provided just our customers even, engineering wasn’t in on it.
TAYLOR: SKL and Jerrold and Entron and C-COR all had systems.
BRIDGETT: Well, I think that…
TAYLOR: Jerrold was forced to get rid of their by antitrust action. In fact, twice they had them and then they got rid of them, and they started again and had to get rid of that one. Both of them by court action. The first batch became H&B America” and that was the first ones they sent off with Leon Papernow, became H&B America”. Then the second time, it became Sammons.
BRIDGETT: Oh, you had question here. Did SKL offer high/low split band two-way before other suppliers? There was a thing we did offer that I don’t think it’s exactly what you mean here. Jake did that. It was down in Maryland, I think it may have been in Jim Grabenstein’s system at Cumberland. I don’t know exactly, or if it was another system there, but AT&T ran it as an experimental thing.
TAYLOR: Oh. Hagerstown.
TAYLOR: Okay, yeah.
BRIDGETT: That may be where we had it, but what we did was we took an amplifier, and I’m not sure if it was a 212 or 211, and we put this in a bridge configuration with high/low filters. Oh, let’s just say band pass, this type of configuration. So you had a pass band here, and you had pass up to this band through this, from this terminal to this one, and pass through this one, to this one. And these things were a little flat thing that sat right under the amplifier. So we did have a two-way high/low type of thing. But it wasn’t the same thing you meant there.
BRIDGETT: Jake might remember better just where that was used but I do remember, Jake put that together and we did use it for something and I think it was an AT&T system we did that in.
TAYLOR: What I was thinking of there was the… after we fooled around with the… we couldn’t do Jerrold and we couldn’t do…RCA was no good, we had trouble with the International Telemeter amplifiers. The next thing we found was Blonder-Tongue MLA amplifier. He had one amplifier for the low band, 2 to 5 and another amplifier for 7 to 13. That was the high/low split that I was talking about.
BRIDGETT: I thought it was that really. Because a lot of people discussed that. We discussed it.
TAYLOR: That was one way of getting enough bandwidth to handle all 12 channels.
BRIDGETT: We did do some discussion of that but the fact is that we started out with an amplifier that went the whole bandwidth, who needed it. Well, I think I’ve got most of the history.
BRIDGETT: One more little point that isn’t in this that I think I would … Oh, test pieces. Yes, I have a … I told you that … Oh, we did several other things. You know who you ought to check on that to. Check with Brooksey because almost everything he got his hands on we sent out to him because he was in the field. So check with him, if I’ve forgotten things.
BRIDGETT: The rumor was that they did some things in bookkeeping they should never have done.
TAYLOR: Who did the things?
BRIDGETT: It was just a careless way of doing things, but…
TAYLOR: By Spencer Kennedy Labs?
BRIDGETT: Yes, there was a lot on the books as work in process and what happened is that they had a large warehouse space and whenever we changed models and disposed of them, this stuff that was work in process stayed work in process, instead of being written off?
TAYLOR: Oh, yeah, written off. You wanted to make some comment about the co-channel filter?
BRIDGETT: Oh, I wanted to get that one for you too.
TAYLOR: Oh, Okay. We started talking about the broadband antenna that you designed in Barre, VT and I asked how can I get a picture of that antenna. Go ahead.
BRIDGETT: Okay, I may have one, and I may not. A lot of my stuff I had framed, been packing and moving got broken. But I do know Nick Sanguenetti kept one for a long time. And Nick, of course, I don’t believe he’s still around, he’s probably is, he’s mean enough to be around still. He’s a fascinating guy. At any rate, his daughter took over the management of the system and they sold out. So there up there on…what’s the name of the street up there in Barre, VT?
TAYLOR: I don’t know it that well, so I can’t help you.
BRIDGETT: Her name isn’t Sanguenetti anymore. So, I’ll try to find out to see if I can get a hold of one of them.
TAYLOR: As I saw it, I think where I saw it was in a Jerrold publication, so I always thought that somebody in Jerrold had something to do with it, but you were the guy that did it. Because I know it came from Vermont. Barre rings a bell now.
BRIDGETT: Yeah. Barre, VT. Well that was an interesting thing. We built a system, we had only channel 4 from Boston. Nick wanted to build a broadband system. Of course, we knew that there were going to be other channels here in Boston.
BRIDGETT: So I designed this horn antenna, 20 dB gain over the whole band. And I built the model up on the roof of MIT using microwave model. And the microwave model worked fine. So when we first built the big model up on the hill there, I had my fingers crossed it really would come out what we wanted, and it did. And that actually sat there aimed at a spot, it was actually tapered horn really, it was aimed at a spot centrally between the ones we thought, there was the Tower of Soldiers Field Road, there was the Needham Farm that was yet to be built and there was the top of the John Hancock building, and I aimed that carefully at just that central point. I called them up good, and they finally came on.
TAYLOR: What do you think the beam width of that thing was, let’s say at half power?
BRIDGETT: Well, I forget, and I did know. I calculated every darn thing about it. But I don’t remember. It was very narrow.
TAYLOR: It must have been very narrow. How long was the horn?
BRIDGETT: Well, this was 60′ ft on the side, vertically and horizontally, and this was shortened. If it had been a straight horn, it would have been enormous length. But I did by tapering it, cut it down to, I think it was not more than about, was less than 200 ft. I think.
TAYLOR: I’ll be darned!
BRIDGETT: But, and then fascinating thing that ties into the other thing we were talking about there was, then a channel 4 in Schenectady came up here. And Nick, incidentally, all he did for these poles, he went out and cut some big trees and built these things. So then the shack is sitting here, he builds another one aimed at Schenectady. And these were not built to keep minor lobes down. They were built for gain, period.
BRIDGETT: Talk about co-channel. That’s when we had to start devising some of those little switch things. That’s what those were for.
TAYLOR: Is that a fact. I’ll be darned.
BRIDGETT: In fact what we had here, these were so darn big of course, that even if we did cancel things, there would be just little small changes of a fraction of degree in the arrival angle here. So, this was not a very stable adjustment either. But what we did anyway, we ran two things in here into the cross run, we ran two in on to the processor here, processor for this one, and then we tapped this one with the splitter and had our attenuator and delay switchers for both for these so we could then cancel each separately.
TAYLOR: Uh. I’ll be darned! Uh. Gee, I hope you can find a picture of those cause, you know in the big antennas, there were these horns and then there are a number of big parabolics that were built in various places. I’ve got some pictures of some of those. And a lot of rhombics, big rhombics.
BRIDGETT: Oh. I have a few other things too I may give you. And I may have still have a copy of a picture of that because I kept it for years, but when I moved a lot of things got packed in strange place, and I haven’t unpacked it. So there’s still a chance.
BRIDGETT: But, on the other side, I’m sure Nick or some of his family would still have it. I don’t know if his family might keep it, but Nick might keep it personally. That’s the kind of thing he would hang on to I think. I know someone else who might have it, I don’t know where he is. I lost track of him completely. Lester Smith had a copy of a picture of that too.
TAYLOR: Would Bob Brooks be likely to have it?
BRIDGETT: Try Bob.
TAYLOR: I’m going to be talking to Bob.
BRIDGETT: Try Bob, he might. And let me know if you find it.
TAYLOR: Oh, you’d like it.
BRIDGETT: I’d like a copy of it too to tell you the truth.
TAYLOR: Very good.
BRIDGETT: Well, is there anything else here. I think we’ve got … Oh, yeah, wait a minute, a couple more pictures you might like, but I don’t think I gave them to you.
TAYLOR: You can take your leash off.
BRIDGETT: [Walked away from mike]
…And they came up with the notion that second order added on a power basis, second order distortion, and I studied the information they had on that. Actually second order in an amplifier like this is self canceling. Revere, that was just torn down a couple year ago, we built all the channels on a single ended amplifier.
TAYLOR: In a 211?
BRIDGETT: Well, that was a Sylvania amplifier, but it was built with an odd number of stages.
TAYLOR: We missed the fact that this was the Bell Lab or Western Electric…
BRIDGETT: It was one of those telephone people…
TAYLOR: Yeah, that came up with the idea that they could be run… that second order would cancel.
BRIDGETT: No. No, they didn’t have it cancel. They said it would add on a power basis, but what it seem to add on was a kind of random basis. But I found out the reason for that. The equalizers that we had at that time were not 1 per amplifier. So your equalization was not perfect at each, that varied, and so the buildup of second order varied with it. The Sylvania amplifiers we built Woburn and Revere with were single ended three-stage amplifiers and in a cascade, each amplifier canceled the second order from the previous one.
TAYLOR: Well, Dan Lieberman had me come up to Syracuse, I think. Isn’t that where Sylvania was?
BRIDGETT: Yeah, I think it was…
TAYLOR: Initially. I think it was Syracuse. Syracuse doesn’t sound right. But any, I went up to there and he put on quite a talk. Do you remember Dan Lieberman?
BRIDGETT: Yeah, I remember him, yeah. I told him about this…
TAYLOR: And he was talking about the intercept that if you adjusted the … he got down to the point where you can actually cancel second order if you put them in right.
BRIDGETT: No, actually it turned out that you can write the equations very easily. And just as with a push pull … when you add these up finally, the distortion cancels …
BRIDGETT: You find that if you take an odd number of stages, or a, I’ve done this too, with an inverting transformer, it works just as well and cascades this thing with inverting transformers, you’ll invert your signal and you’ll invert the distortion. But the double inversion on that means that at this point, you cancel all even order, not your second order, all even order.
TAYLOR: Well, this is pretty close to what Lieberman was talking to me about.
BRIDGETT: Well, the big thing is, that in general, with a distributed type amplifier, it kind of hard to talk about an inversion, you know it’s time delays and so on.. So I described to him a way that if you worry about that you get the same effect if you plot back delays if this comes back to a pi over 2 …
TAYLOR: There you go. That’s what Dan was talking about. Yeah.
BRIDGETT: And that came from conversations with you?
Yes, but the thing is because of this, I recognized when we bought the Sylvania stuff, that this had that possibility, so I ran some tests on it, and somebody ran some test on running multiple channels on the Woburn system, was surprised that you could do it on a single ended. They never did put in what they wanted, but I knew when we came to Revere that we needed more channels, it was sitting there waiting for us.
TAYLOR: I’ll be darned. I got hired by AEL. Remember AEL?
BRIDGETT: Yes. It was AEL with…
TAYLOR: Yes, cause Walt Wydro had been the consultant I guess, with AEL and maybe an engineer with them. And he went with Dan Lieberman up in Sylvania.
BRIDGETT: And it was almost a copy of the AEL amplifier.
TAYLOR: But, AEL called me in, this was after Wydro was gone out of there, but they were using this single-ended, second order phenomenon and they needed desperately, cause AEL was getting in trouble in the CATV business as well, and they wanted me to make a statement endorsing this idea. And I was scared to death of doing that because we tried everything we could to avoid endorsing anybody’s products, but they kept hounding me and hounding me and hounding me and finally after we spent about 2 weeks in the office of Malarkey-TAYLOR: just, how can we handle this. And I finally came up with a statement that said that both the single ended and the push-pull approach depend on phase cancellation and as far as I was concerned, the proof of the pudding was in the eating. If you think it worked, it was fine. But I didn’t say that one was better than the other.
BRIDGETT: All you had to do was to put two of them and cascade and then check them out. This was the thing with Sylvania. We built those two systems in Woburn and Revere with some Sylvania stuff, and then they started, oh they got to go to push-pull because everybody wanted push-pull, so they started a line of push-pull. We got a few of those. So, by that time, I’d gotten a decent bench setup down there, and I did set up cascades, even numbers of single-ended and even numbers of push-pull and their single-ended always came out better on second order than push-pull.
TAYLOR: Is that so?
BRIDGETT: It’s an interesting thing because they couldn’t make their push-pulls balance as well as they thought they could. And so, it was always some measure of single-ended to the push-pull.
TAYLOR: Of course, I remember from the old audio days that it was a real trick to get the two to push-pull balanced and it always puzzled me that they could accomplish it.
BRIDGETT: Well, you see what happened there again was your audio transformers were not as simple as they seem to be at high frequency end. And of course, that’s the same thing here too.
TAYLOR: These weren’t simple and with the broadband you were doing an enormous bandwidth.
BRIDGETT: Yeah, but again what I found that I could do, I could take these things out and put a inverting transformer in each one and improve them.
TAYLOR: Well, this picture here, where that intercept came was somewhat controlled by the voltage on the transistor.
BRIDGETT: Well, this is the thing that you could get into that you build a line like this. And, of course, there’s a delay presumably you follow as closely linear with frequency in it should intercept at 0. But if there is a phase inversion, or polarity inversion, it will just do that.
TAYLOR: But they can…AEL and Dan Lieberman showed me how they can just change the voltage on the transistor and move that thing up and down.
BRIDGETT: Yeah, at very small amounts.
TAYLOR: So if he could get that to, I think he was trying to get it to about 90 degrees, that it would then invert in two stages and …
BRIDGETT: It was like the feed forward that George Ray had a hard time convincing … You didn’t need it that good.
TAYLOR: Okay. Okay.
BRIDGETT: You could throw it together and it worked.
TAYLOR: Yeah. SKL never did anything with that second order phenomenon we were just talking about.
BRIDGETT: No, well actually, I don’t know. I never could get Lester interested in it. You see, what happened there was if we had tried to put an equalizer in each amplifier, so they all came the same level, that would have shown up differently on the tests at Bell Labs and we’d have had a collision, but I’m partly to be blamed for that. When it came to doing the equalization, I have reams of point to point plots on the amplifiers and I got good averages on that, and of course they had a shape of their own. What I tried to do was to take standard plots in the old motion picture handbook…
TAYLOR: Uh huh. Uh huh.
BRIDGETT: And see what I could match together with that would come out closest to the square root of frequency. And I didn’t care how big they were, as long as they were usable, and so they were not one for one per amplifier. You waited until you accumulated enough cable and so you ended up till you were actually rocking the system this way.
TAYLOR: Well, now SKL used the external thermal sensor for slope control or just gain control.
BRIDGETT: Well, we did several things there. We had, of course we knew we had to have an automatic gain control very quickly, we built Barre without automatic gain control and found out very quickly. So what we did there, we bought one or two Jerrold strip amplifiers. We only had one channel at the time. Stuck them at proper intervals and made the thing live while we got to work on that. And, so we first got an AGC …
TAYLOR: Barre was aerial on poles.
BRIDGETT: Yeah. Then what I did, I started trying to design a two pilot arrangement on those old things. And I did do a thing …
TAYLOR: Gosh, that was way back then.
BRIDGETT: It was way back. I got one that almost satisfied Bell Labs. I did an interference between two signals that slipped out of phase slowly. When you’re designing these distributed amplifiers, you had to allow for a little of that, not a new trick at all. But trying to design a new shape finally that would change because of the addition of two slightly out of phase. I never did get the shape exactly what I wanted, but it was enough to where they were pleased with it, so that this way could work. Then we started in with straight thermal tests. We began to get some good thermistors that we could play with. And I think we ran for a long time, as most people did, with just thermal for the slope. And then of course, there were people like Jerrold, who tried to put slope and gain on one pilot which, you can make it work, but …
TAYLOR: But it wasn’t too bad when you were only up to channel 13, but it was when you started to go into the higher bands and more channels it was a little more difficult.
BRIDGETT: In fact, way back in the early days, we were going to have to have two pilot systems and when we get enough channels we’re going to have to have three pilot systems. We never did get to three.
TAYLOR: Yeah. We never did to three.
BRIDGETT: Actually, we kept pretty good control over shape finally. I know Jerrold came in with the weirdest notions that you had to have a special shape for each cable. I never saw anything except our old set. You had to buy one set of equalizer if you were using this cable, another set if you were using that. It was baloney. The accuracy to the square root of frequency was very good unless you got to very narrow center conductors.
TAYLOR: Well, the 412 was pretty small.
BRIDGETT: But as long as you consider that the diameter was pretty large compared to the skin thickness, then you treated as … frequency very accurately.
TAYLOR: Don Spencer, in my conversations with him, was always “gung ho” on type N connectors, but type N connectors are pretty impractical for a cable TV operator. What was the attitude about connectors? What did you do? What did you use?
BRIDGETT: We worked, we took type N to begin with. In fact, we had pretty good business, type N 75 ohms was… I think it was SKL’s business to get that to be a standard type connector. But we constantly looked for less expensive connectors that would be adequately close to 75 ohms. We tried every kind of microphone connector there was, everything else, put it on bridges and checked them out. The interesting thing, the Jerrold type C, I was fascinated about it. It was a cheesy little connector that fell apart. The F, I thought, was a real tour de force when that came along.
TAYLOR: You know, Ken Simons tells me that the C-connectors was only a 30 ohm match.
BRIDGETT: It was pretty hard to make tests on it. Pretty hard to put it together that would stay together too. We had one microphone connector that did pretty good up through channel 13 and we used that a little bit with a hope that maybe this would do, to try to help some our interconnections…
TAYLOR: Did you use the old UHF, so called UHF PL-259 type
BRIDGETT: No we didn’t. They were too far off. At low band up through channel 6, you could get by with them, but go up above that, it was …
TAYLOR: Earl was telling me that somebody in their outfit, I can’t remember who it was, really got interested in developing connectors. And so they did a big modification of the UHF. But it was never very widely adopted by the industry.
BRIDGETT: But I have seen some, I forget what, they had a number for it, but they made the center conductor a little bit narrower, so…
TAYLOR: Yeah, they got the impedance proper.
BRIDGETT: Closer to what it should be at the higher frequencies. Some of those linemen working up on the pole, up in Barre. Lloyd, an old power company lineman… he was used to everything that’s done with a big wrench and everything and here he’d put these little things together. But he’d do just what you told him. He’d make splices directly on the cable, and this is the way it’s got to be, this is the way he’d make it.
TAYLOR: RCA came out with a pressure tap that had about 35 little tiny pieces. You’d get up on a ladder or on your spikes on a pole trying to put that thing together and you’d drop a piece, and it was gone. Oh that was miserable thing.
End of Tape 2, Side B
The substantive interview was completed. No additional conversation was recorded.