[Milsurplus] TBW on the air

[Ray Fantini]

Cool, I had the center section but when I bought it had been hacked bad so had no issues building modern AC power supply. Did use the stock suppressor modulator and the plate current meter. Had separate power transformer for the 10 volt 803 and adjust rheostat for setting the filament on the PA, although the meters had printed on them for use on 800 cycles they worked well on 60 cycles.
Had a 400-volt power supply and a 1600-volt supply and used the original keying system that controlled the AC voltage to the B+ and HV supplies thru the huge keying relay. Did have solid state devices for both power supplies so the issue was that when you let up on the key or PTT the filters still had enough juice to produce a chirp that drifted down the band on the receiver that was annoying, but by biasing the IPA tube to cut off without drive that solved that problem. Although I was at the time and still am the world’s worst CW operator still wanted full brake in keying without chirp.
My TBW was my first good AM transmitter and always got good reports as to the quality of the audio so the suppressor system worked surprisingly well. Was trying to do AM with a TCS before the TBW and low power sucks.
Would someday like to find a TBW carcass that can be taken apart and be used for building a “Old School” nineteen inch rack transmitter using the same LO/IPA and PA but instead of using the suppressor modulator use a high-level plate modulator. Maybe even do something crazy like doing parallel 803 tubes and high-level modulation being that output tank for that transmitter is built like a tank and can take it.
One last thing though, I did modify my output for 50 Ohm coax and operated using antennas cut for each band so it was around 50 Ohms all around and with this I also ran one of those old Johnson TVI filters and that kept anything in the third and fourth harmonic or any other wide band noise from the PA forty to 50 Db below the carrier, did not care about TVI just wanted to keep it clean.
The last couple months been working on a system that converts 60 WPM Radio Teletype over to 300 baud ASCII with building up lots of digital circuits, would be good to get back to something with huge tubes and tanks  again!


Ray F/KA3EKH

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