[TenTec] Omni C AGC problem after mod.

[K & H Darwin]

----------
> From: Steve Ellington <N4LQ@iglou.com>
> To: K & H Darwin <darwin@together.net>; TenTec List
<tentec@contesting.com>
> Subject: Re: [TenTec] Omni C AGC problem after mod.
> Date: Saturday, February 26, 2000 8:06 AM
> 
> 
> Due to lack of information I will make a few assumptions.  If your are
> referring to the 4.7uf capacitor (C22) on the I.F.-AGC board as the one
you
> reduced to 1uf then that's fine and it will shorten your AGC decay time.
But
> putting that 3.3uf cap across the QSK switch was certainly the wrong
move.

Oops, let me clarify the mod I did.  Yes, I replaced C22 with a 1uF cap.  I
reused the QSK switch by disconnecting the wire from the QSK pin on the
Audio-Sidetone board and tying it to the ground side of the new 3.3uF cap. 
The + lead of the 3.3uF cap was wired to the + lead of the 1uF cap, putting
them in parallel.  So, when I switch the QSK switch from fast to slow, I'm
connecting the 3.3uF cap to ground and getting 4.3uF.  With the QSK switch
set to Fast, I'm getting only the 1uF cap for fast AGC.  In this case the
3.3uF cap is still connected but the ground is interrupted.

Another option I've considered is doing the same thing with C25 to produce
short and normal hang times.

Keith Darwin
KD1E
Ferrisburg VT
Omni C

> > I modified the AGC circuit in my Omni C to speed up the AGC on RX.  I
> > replaced the 4.7 uF cap with a 1 uF.  I then wired another 3.3 uF cap
in
> > parallel through the Fast / Slow switch.  The mod works well, giving me
> > both normal (slow) and fast AGC responses.
> >
> > But now my QSK is messed up.  When in Fast mode, the receiver takes a
long
> > time to recover after transmitting.  So between dits and dahs, the
> receiver
> > is on but the sensitivity is greatly reduced, nullifying the QSK.  When
I
> > switch to Slow the receiver recovers quickly between code elements and
QSK
> > works as it should.
> >
> > Any ideas??
> >
> > Keith Darwin
> > KD1E
> > Ferrisburg, VT
> >
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> 
> 
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