[TenTec] Corsair II sidetone revisited

[Tommy]

Yep. Lotta fixes for the 'buzzsaw'!!

Check N1EU (may have that call incorrect) website for several C II 
mods, including a replacement audio sine wave generator designed by 
N4LQ. Filters work, the SCAF on the C II's audio output will clean 
up the square wave harmonics. What I did on the TT units that had 
the UJT square wave 'buzzsaw' sidetone was get an old TT active 
filter (think it was a model 250 or 205) physically mount it on the 
side of the chassis, with it hanging out over the audio board. Then 
removed one of the series resistors in the sidetone circuit and 
connected the active audio filter (op amp filter) is series with the 
sidetone, feeding the audio amp. Worked excellent. Since the UJT 
generates a square wave, you have the fundamental and ALL of the 
harmonics, so what you are trying to do is just get rid of the 
harmonics (of course). The mods are relatively simple to do.

If you can't find the web site, let me know and I'll look it up and 
send you the URL. My half-asleep brain cell says its something like 
www.qth.net/n1eu

Tom - W4BQF

----- Original Message ----- 
From: <k7gt at charter.net>
To: <tentec at contesting.com>
Sent: Tuesday, November 09, 2004 12:09 PM
Subject: [TenTec] Corsair II sidetone revisited


>I just did a thorough search of the TT archives re a
> solid fix to the buzz saw Corsair II sidetone. G3JXS
> had suggested and implemented an active filter solution
> with which he was pleased. Others said that such would
> lead to enough delay to affect QSK. It would seem that
> a simple one- or two-stage passive filter might have less
> delay and thus suffice as the 2nd harmonic is at about
> 1300-1500Hz (my sidetone is set at about 700 Hz, I was
> trying to match the 750 Hz CW offset but couldn't go
> quite that high). Before I dive into the books in an
> attempt to design such, has anyone on the reflector already
> done so?
>
> BTW: I used one of my Corsair IIs in SS this past weekend.
> (I am not quite through with the permanent station
> setup with the OmniVIs after our recent move and am using
> the C-II in a temp setup). I had a ball. The biggest
> problem I had in a contest setting was quickly and
> accurately zero-beating the CQing station. The SPOT
> button give a fairly soft and deep (!!) pitch to center
> on 0 Hz and the sidetone, as mentioned above, is neither
> matched to the offset nor harmonic free for a pitch
> matching method of zeroing ala OmniV and OmniVI.
>
> 73  K7GT
>
>
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