[TenTec] Corsair 2 not stable on receive, 20 meters

[Lee WA3FIY]

There is no 20 meter heterodyne oscillator in the Corsair II (or many other Ten-Tec's of that 
vintage).  On 20 meters the 5.0-5.5 Mhz PTO is directly mixed with the 14.0-14.5 Mhz 
incoming signal to produce the 9 Mhz receive IF.  The BFO oscillators come into play on all 
bands but since 20 is the only band where Dwight is having the problem, that pretty much 
rules out the BFO leaving the PTO as the primary suspect.

73,

-Lee-


On 20 Jan 2015 at 13:31, Katz Ajamas wrote:

> >
> >
> > From: Dwight Orten <dwightorten at gmail.com>
> >
> >
> > My I been working PSK with my old Corsair and I am starting to have
> > trouble on 20 meters.  Watching the waterfall, the incoming signal
> > drifts off and my software can,t decode it.  Sometimes it comes
> > back, sometimes I have to chase the signal.  I don't know if it is
> > doing the same on transmit.  The frequency readout is not showing
> > any change when this happens.  On all other bands the waterfall
> > lines are straight as an arrow and no trouble coping.  The PTO has
> > never been rebuilt, but it seems to me if that was the problem it
> > would be on all bands. Any thoughts, anyone? KM4FO Dwight
> >
> 
> Dwight-
> 
> I don't know the Corsair but based on it's age... Perhaps component
> value changes.
> 
> In some of my older tube gear it has led to poor stability of a
> heterodyne xtal oscillator. You can check if you have another RX you
> can lay an small antenna near to and tune to the freq of the
> heterodyne osc for 20m to check stablity.
> 
> Maybe you are working a bunch of drifty guys on 20 ;-)
> 
> 73,
> -Bob
> ah7i/w4
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