[ARC5] BC-221 frequency meter

[Ian Wilson]

I have tried several ways to do this in the past. One difficulty is that
the output
level is quite small, and the source is high impedance. Fine for coupling
weakly
but not adequate drive for direct use into a transmitter. Another
difficulty is that
you will have strong backwave from the continuously running VFO.

Have spent some time on a heterodyne VFO, where you use a keyed crystal
oscillator as LO and mix with the BC-221 signal to get to the frequency you
want. This also allows you to insert some gain to get a decent level of
drive
signal. My best results so far have used a cathode follower at the BC-221 to
drive a shielded cable to a small chassis with the xtal osc and mixer. I
followed
this with a double-tuned filter and 6CL6 Class A-ish amplifier.
Unfortunately
the output stage has proven to be somewhat difficult to tame.

For the hybrid-minded, I would imagine that you could use an NE602 as
xtal oscillator/mixer plus a plastic RF "power" transistor to boost the
signal
and fit it all in an Altoid tin (spray with camo paint so it doesn't look
too bad
hanging off the front of the BC-221 <g>).

73, ian K3IMW



On Wed, Jan 1, 2014 at 7:16 PM, JAMES FALLS <radio-tuber at att.net> wrote:

> I have a spare BC-221-AK that is "caseless", bookless and took a beating
> in the past, but seems to work OK. Anyone use one as a VFO? Would
> capacitive coupling and an adapter be the best way to drive a crystal-bound
> TX like a WRL-680-A?
>
> Wool gathering............
>
> Jim K6FWT
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