Not for a '21 but years ago I did on an Argosy. I made a simple class A buffer
of the VFO (so if anything happened to the line out, no impact to the VFO) (no
I don't remember how! rig got traded long ago) and ran it to a 12V accessory
socket. The 12V line was reattached through 100uH+10uH chokes, that way I
could power the remote readout and have have the VFO on one coax line. And if
I goofed, then whatever was plugged in would work just fine, the buffer would
prevent loading on the VFO, and the 12V line would power readout or accessory.
Worked well.
I've been messing around with sidetone boards, made one for my Corsair II, and
TBH it's probably overkill (but much fun all the same). LM555 followed by a
tight filter. Ironically I'm now up to two 21's in the last six months, and
I've already forgotten what I did to try out a different board...
Anyhow. On the audio board in the 21 sidetone is generated by the same IC
doing filtering. But you could pull C2 (or R5)(?) so as to disable that, then
inject in whatever you want. If you are using an external keyer, they often
have their own sidetone. Or you could make up your own oscillator and bring it
back in, via the sidetone path. I picked up recently an OHR HP 40m QRP rig,
which is a comercial "QRP Optimized Rig" by W7EL (file at ARRL) which I thought
had a good sidetone. LM3900 Norton amplifiers I'm not very familar with so I'm
not sure how much I'd want to mess with one, learning how they work, as they
are kind of a dead branch on the tree: I think I'd rather make some perfboard
wonder and tack that in.
Shawn kb1ckt
On Monday, October 24, 2022 at 10:14:22 AM EDT, Josh Gibbs
<gibbsjj@gmail.com> wrote:
Take a look in my C21 files:
https://drive.google.com/drive/folders/0B_pjAwEfeYcdYmRaTUhRTnN6SFU?resourcekey=0-hhVeFiru-1csSZZez-phbA&usp=sharing
In the 'Modifications' folder, see the 'Little Extras for the C21' PDF. I
have not done this mod to my C21 as the sidetone doesn't bother me that
much, but I agree that it sounds pretty bad! I thought something was wrong
with my C21 when I first got it until I found out they are supposed to
sound like that =)
-Josh WU7H
On Sun, Oct 23, 2022 at 3:12 PM Michael Goins <wmgoins@gmail.com> wrote:
> 1. Is there a fix for the awful sidetone on the Century 21 rigs?
> 2. Anyone done a digital dial addition (external) for the Century 22 using
> maybe the Hendricks kit?
>
> Mike, ww5wm
> w <http://www.youtube.com/watch?v>ww.bella-green.com
> *http://www.youtube.com/watch?v
> <http://www.youtube.com/watch?v>>www.bella-green.com
> <http://ww.bella-green.com/>*
> STDX, TDXS, FISTS, QRP-L, ARS, SOC, Flying Pigs, IQRP, AQRP, QCWA, RSGB,
> QRP-ARCI , NAQCC, One of many past editors of QRP Quarterly, Mensa.
> _______________________________________________
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>
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