[TenTec] Sidetone thump

[Dr. Gerald N. Johnson]

On Fri, 2009-12-04 at 04:17 -0800, g p wrote:
> Recently acquired a Corsair, works well but the sidetone thump kind of bugs me a little, I did the sidetone mods as per Ten Tec wiki and it sounds better but there is still a thump that increases as the power out is increased. Now I can live with it but boy it would really make it much more enjoyable taking out the thump, this thump happens with either slow or fast QSK.
> Input appreciated, thanks
>  
> Gil
> 
I don't know the circuit of the Corsair and I don't recall any such
thump in my Corsair II though the sidetone is raspy. The sidetone
oscillator is a relaxation oscillator because it starts and stops
instantly, and that start and stop probably makes the thump. I'd look at
reducing the size of the coupling capacitor out of the oscillator to the
point it begins to reduce the sidetone level. That will reduce the
energy from the DC keying of the oscillator that you hear as thump. If
there are multiple coupling capacitors after level set or gain stages,
reducing each of those will improve the thump rejection.

73, Jerry, K0CQ