Updated 20 Jan 2001, AB4YD
Bill's glowbug project #2, 80M VFO rig with 807 final, Rev E
This project was inspired by a series of QST articles by Hayward,
W1PH. I based my rig on his April 1962 article, "Have You Tried 160
Lately?". I liked his simple, single band rig. I thought his use of
6V6 tubes, along with regulated voltages, to be a simple but stable
alternative to being "rock bound". You can read about his "coffee
can" VFO, in the August '49 and Sept '51 issues of QST.
However, I ignored his approach to mounting the VFO part of the circuit
in a sturdy coffee can, and just put all of the circuits onto the same
chassis. It worked, but it was very microphonic, and this made it difficult
I eventually chose another route for the VFO, and used a separate chassis
for the VFO circuit. Along the way, I also changed the VFO tube to a 6C4, mainly
to reduce problems related to heat. The
output was very low, so I added a 6AC7 stage. I also went to a 1/2 freq VFO,
and doubled the frequency to 80M just in front of the 807 final.
I am pretty happy with the stability of the VFO. The output from the 807 seems
a little low, but perhaps it is due to my low B+ and 250V screen. I get about
20 watts into my 50 ohm antenna, even after going thru my half-wave output
filter. All in all, it was a fun project.
Old versions of the schematics
Selected info about receiving tubes, from the GE essential
characteristics tube manual, date unknown, perhaps '50s or '60s?
Tube data for a few tubes I am using
OLD PROJECTS from previous years (1999)
Bill's glowbug project #2, 6AG7 / 12GT5 transmitter (didn't work too
good. oh well)
Bill's glowbug project #1, test circuit for oscillator