The AM Forum

Greetings
I have a mint condition BC-221 that works. It's very stable and quite precise considering it's age.
I thought it would be cool to use it as the VFO for my BC-610 E. Unfortunately, it only produces about
1 volt RMS out, so I need a buffer stage to bring that level up to a higher value, perhaps 10 volts.
Could anyone point me to a circuit that would work? The power supply I have is setup for 135 VDC B+
and 6 VDC for the filaments. I am hoping to have the BC-610/RCA AR-88 ready for Christmas.
Thank you for reading.
73 de Billy N6YW

B,

 You might check out a ARRrL handbook. Lots 'o schematics in the HF Transmitting section. There are also various "west coast" handbooks availoable.

http://www.tubebooks.org/Books/intro_orr_radio.pdf

gud luck... I've intended to use my 221 for  a VFO in my 813 rig, but I'm lazy and haven't go to do it yet.


klc

Thanks for the reply.
I have several editions of the Bill Orr & ARRL books going back to the 40's, plus many others.
Perhaps I am looking for a mod specific for the BC-221 although it seems that most any buffer
circuit would work at HF with the right tube and layout. I have never built an RF buffer before,
so even though I build guitar amps for a living, the concept should be the same.
73 de Billy N6YW

There is a brief section on using the BC-221 as a VFO in the "Radio" Handbook (west coast) in a late 1940's edition, I think maybe 11th or 12th ed.  The green edition that was larger format than the others.  Some considerations are that the 221 is rather rich in harmonic energy by design, which may or may not be an issue depending on design considerations downstream,  but they are certainly stable.  I was thinking that would be a good application for those instruments missing the cal books, although it's possible to make your own replacement cal book as well.