[Fwd: [TenTec] 1220 Audio and PL Fix.]

[Bwana Bob]

This may fix your audio problem. It worked for me in increasing the mike
level and reducing distortion as well as cleaning up the CTCSS tone.

			73,

			Bob WB2VUF

Robert Weingaertner wrote:
> 
> My 1220 2 mwter transceiver was plagued with an excessively loud PL
> (CTCSS) tone and somewhat weak transmit audio. I had tried extra grounds
> on the power amplifier assembly and some extra grounding on the VCO
> shield can. I even added extra shielding and grounding here and there
> in the form of foil tape. These measures helpd a little bit but didn't
> really correct the problem.
> 
> I reasoned that the CTCSS tone was getting into the VCO by some path
> other than the intended one. In playing around with bypass capacitors,
> I discovered that I could improve the transmit audio AND reduce the
> CTCSS tone amplitude by increasing the value of C36, which bypasses the
> collector of Q14 to ground near the VCO. This fix is best accomplished
> by soldering a .01 uf cap across the C36 pads on the underside  (foil
> side) of the board. Make the ground lead a little longer so that it
> reaches from the ground pad to the bottom VCO shield to provide another
> ground point for the shield.
> 
> 
> By the way, the 1220 works extremely well on packet if the receive
> audio is taken from the detector via the DIN connector and not the
> speaker line. I had to modify my KAM TNC to make it more sensitive, but
> this mod is provided in the QRZ CD ROM. After switching to detector
> output, I was able to work packet nodes reliably that I could never
> even connect to in the past.
> 
>                                 73, Bob WB2VUF
> 
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