[TenTec] Corsair II Double Side Band Board (BFO) Problem

Dave Humbertson w3np at atlanticbb.net
Mon Nov 14 14:12:25 PST 2011


  Dave,

It sounds like the normal 700 hz offset found in the CW mode. From what 
you described your rig is working properly. Your TX and RX are offset by 
700 hz so you hear a 700 hz note when tuned to the transmit frequency.

73, Dave - W3NP

On 11/14/2011 5:02 PM, David and Dianne on Comcast wrote:
> Hi Everyone,
>
> After a 10 year hiatus, my love affair with
> Corsair II has resumed after I recently acquired a
> pristine sample of this transceiver. It came to me
> nearly flawless regarding electronics, mechanics
> (switches and PTO etc.) and cosmetics. This is one
> fine transceiver to use on CW and SSB. My K3 has
> been sitting idle for a while now.
>
> But as received, it was obvious that the BFO
> frequencies were not correct for SSB producing a
> very pinched audio. So I replaced the stock SSB
> filters with INRAD 2.8's with a great improvement
> in SSB fidelity as I had done in my earlier CIIs
> from the mid-1990's
>
> Against my better judgment, I tweaked the trimmers
> on the DSB board tied to the 9.000 MHz crystal and
> of course got things messed up.
>
> The CII manual states that calibration of these
> trimmers (C1, C2 and C3) on the 80980 DSB Board
> requires a frequency counter. This is a piece of
> equipment that I have never owned.
>
> I was able to get SB-N and SB-R spot on by ear by
> zero beating against WWV 10 MHz and using their
> 500 and 600 Hz tones that alternate each minute
> during the hour. (I zero beat WWV in SB-N and SB-R
> against a 500 and 600Hz audio tone generator
> program on my computer). It's easier to do than to
> explain.
>
> Here's the problem. While SB-N, SB-R and my CII
> frequency counter are now spot on against WWV, my
> CW Rx frequency reads 700 Hz low against the CIIs
> frequency counter. I assume that TX frequency is
> also low as I have no trouble getting CW calls to
> respond to me on my frequency.
>
> In SB-N and SB-R it is reading correctly, just not
> so in CW. It's a minor annoyance that I can
> mentally compensate for but I would like to get it
> fixed if I can.
>
> Can anyone recommend a procedure for doing this
> 'by ear' without a frequency counter?
>
> And if in the end I need a counter, can anyone
> recommend one that won't break the bank? I have
> seen many on eBay etc. for relatively modest cost.
> I know that  a high quality counter can be expensive.
>
> I have seen several "Leader" Nixie readout
> counters in the used market but know nothing about
> them. I have also seen a mini-counter kit from
> Cumbria Designs in the UK and a Chinese counter,
> the LDB-TFC2700L.
>
> Finally, I fitted Phil's (K4DPK) PTO stabilizer to
> the CII with outstanding results. It makes the PTO
> extremely stable over long periods of time. The
> circuit works as advertised, is an easy install
> and Phil is a great guy to do business with. The
> remote VFO is next.
>
> Thanks  any suggestions.
>
> 73 de N1LQ-Dave
>
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