1930s Transmitter Update

dscf7164-croppedThis year’s Field Day transmitter employed a 59-59 (ECO/Buffer) exciter and Push-Pull 804 amplifier.  While it worked relatively well for the circuit in use, I wanted to get better performance out of the exciter.  Tuning was very critical at each stage due to insufficient isolation (incomplete screening in the 59s), causing chirp and in some cases a raspy note when optimal settings were not used.  A particular “good” setting of the tank tuning at each stage was also only good for 10-15 kc before re-tuning was needed to clean up the signal again.

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W8CDX 2017 Field Day

Video courtesy of Mike, WA3TTS

We had a lot of fun putting up another 1930s style station this year for Field Day 2017.  The station was 100% homebrew, with the transmitter and receiver being based on articles in the August and May editions of QST respectively.   The link coupled tuner was based on the 1936 ARRL Handbook.  The power supplies were based on standard designs from that era as well, using 866s in the amplifier supply and 83s in the buffer and oscillator supplies.  The bias supply used a type 80 rectifier and a 874 regulator (late 20s tube) for -90V bias. Continue reading W8CDX 2017 Field Day