The AM Forum

 :)  OK, I went digging and came up with gem that Ed K9 Fuzzy White Rabbit drew for me, so I think this is it.  If I use this with a B+ of 180 regulated for the plate and screen, the only thing to change might be the screen resistor.  I think 15 K would cover it.  I'll feed a 6Y6 with maybe 280 volts.  Comments?

Biased Class C?

I think the grid resistor should be 22K.  Whoever heard of a 221 ohm resistor?  Obvious misprint that slipped past me.  For some reason the 1 should have been a K, same as the 47 in the screen which I corrected.

Nice ECO.  My first HB novice transmitter was similar but used a 3 to 30pf variable padding cap. in the grid circuit, where you show a fixed 47pf, for best keying characteristics and crystal start-up when keying.

Also ran B+ on plate unregulated but put a couple of OB2's in series for 216 regulated on the screen. Don't forget to calculate and add dropping resistor.

Also ran into a Pi net with output of about 20 watts .

Very good tone and very little chirp but some crystals didn't work as well as others.

It was in the 1963 ARRL handbook using a 6Dq6A with a 150 ma meter in the cathode.  Also to eliminate key clicks the cathode resistor was right off the key jack instead of directly up under the cathode tube socket pin.  Meter in-between with 1000pf on both sides to ground.

B+ was 375 volts, dropping Res. to OB2's was 10k/10watts.

Ed, K9FWR down in Manitowoc, WI has an absolutely fantastic line up of HB gear.  He was CE for a broadcast chain for years before he became the regional CE for AT&T designing cell phone systems.  He drew up this design for me several years ago.

This design called for 350 VDC and I know a basic 6AG7 oscillator/ transmitter like the one in the November 1953 QST will run 7-10 watts input at that voltage.  I have a couple of VR-90s so I can drop that down to 180.  Keep in mind this will be the oscillator for an exciter, AM only.  I considered using either a 6Y6 or 6F6 PA neither of which require much drive at all and the output requirement to drive an 813 would be under 5 watts.  My objective is a stable peanut whistle that I can follow with a final running up to 250 watts.

I have a Kenwood 440, Heathkit DX-20 and DX-60B for CW so this rig will be AM only.

Circuit looks good.  Depending on your frequency counter input impedance you may load the oscillators output down a bit with the tap at the top end of a parallel resonant circuit which is the high impedance point in the circuit.  In addition when you connect and disconnect the counter the variable capacitor may need to be re-peaked up a bit.  This is easily fixed by tapping up from the ground side of the parallel resonant circuit through as small value of cap as you can get away with.  You don't need much voltage since most counters are pretty sensitive. 

Joe, W3GMS   

The frequency counter won't be in the circuit permanently.

Great circuit. Later you can tack on a 6L6 or 807 PA. My novice rig was that 6DQ6A crystal cracker from the HDBK.

 :) Thanks!  I might make it modular. That way I can follow the 6AG7 with anything up to and including an 813.