This is the Gates Radio Section of
1,000 watt Transmitter
The BC-1T was a solid performer, which eventually grew into the BC-1G. Using 833 tubes for the modulator and power amplifiers, the BC-1T was an efficient unit, well designed for the increasing modulation requirements of the 1950s and 1960s.
Phil Alexander says: Both cosmetic and cost surgery on the cabinets. Square corners are so much cheaper than anything more esthetic. Harris insisted on a VA (value analysis) program which was a major buzzword when they bought Gates in the late '50's. Ed Gagnon (pronounced GON-yo) was their PR honcho at the time and he headed up the program. (!) The directive came from Cleveland, not from Parker Gates. This gave birth to the BC-1T (tin can) succeeded a few years later by the 1G.
Then they started with the xH boxes beginning, I believe with the 10H then 5H etc. The same program resulted in the FM-xxG/H series. Notice how all the H's were hybrids - low level SS, high level tube? The only reason the BC-5/10P's were exempt from going through a "G" phase was the cost of two quick design changes and the cost versus the lower production volume. In those models they went directly from the "P/P2" designs to the H which IIRC was introduced in '67 or '68 just after the BC-1G and at about the same time as the TE-1 exciter that shifted all the FM's from G to H.
|The BC-1T was introduced in 1957.|
|The BC-1T was the first transmitter to be supplied with a built-in dummy load. It is in the center of this picture, on the left wall of the transmitter.|
|833s make great light bulbs, don't they?
Oddly enough, there are some high end audio amps advertised on the web using 833s. While I'm a little nervous about any exposed tube with 2 kV on it, apparently some people would not be so....
|Even better at night!|
Phil Alexander says: Then, the "T" got a very bad rap because the driver boards were originally the height of stupidity in design. The Harris drive for even more economy had become a fact of life at that point (circa '67~'68), but sales were going south and the 1kW was bread and butter so marketing demanded a new dress for the now beautified pig and called it the 1G
The biggest problem with the BC-1T/1G was the design choice Gates made. I worked in Gates field service when the transition from 1T
to 1G was going on, so I saw it all.
The drivers were underpowered because they used 807's to avoid using an intermediate HV supply around 1.5 kV as most other 833 designs did. In the 1T design they used the 6BG6 rather than the 807 and mounted it HORIZONTALLY even though the RCA manual had a major warning that the tube was to be used ONLY in the vertical, base down position.
The retrofit boards were made available free for the asking and notices were sent out. AFAIK all boxes were converted to 807's with green phenolic boards. The 1G version used the same boards however, the horizontal mounting was not kind to the 807 either. The problem was cooling air flow. That was the reason for vertical mounting. A small fan blowing across the cards could have solved that problem.
However, the 807 boards did not have the output needed for driving the 833's to end of their useful lives. Yes, there were no problems with new tubes, but there was no excess, unlike other designs that used higher voltage tubes like 813's as drivers.
To be fair, Harris who owned Gates even then, gave engineering an impossible task. They wanted 833's to differentiate them from Collins so they could capture the market that "didn't like them newfangled tetrodes" yet they had to keep the manufacturing cost in line with the tetrode competition. The result was shaving as many corners as they could, and still ship a working box with acceptable reliability.
The result was probably the largest selling transmitter ever because the Class IV's bought hundreds of 1/250 T's and G's as they made the transition from 250w unlimited to 1kW day/250W night broadcasting.
Personally, I preferred the modified 1T to the 1G, because access to
parts was easier, but neither was very hard to work on, and the
design was "plain ol' country radio" as a major market chief I knew in those days described most things built in Quincy.
So far as modification are concerned, if I had to run one today, the first thing I would do is get some large angle bracket, turn the driver boards horizontal and blow air across the tubes with a couple of 4" muffin fans. The second thing is correcting the capacitor values in the modulator circuit to raise the efficiency above 5 kHz.
I don't think I'd go much further although there are several things that might be done, because my next step would be looking for used ND-1 or a new BE AM1A, or maybe even a new DAX-1 to install as a main and use the 1T/1G as a backup.
Phil Alexander, CSRE, AMD