[Elecraft] [XV432} LO Instability Problem

[Don Wilhelm]

Ian,

Two possibilities occur to me.  First, detune the LO inductors L3, L4 
and L5 a bit to give you 3 volts maximum at TP1 and see if it stabilizes.
Secondly, try adjusting L4 a bit.  It may be that the adjustment of L4 
puts the crystal right on the 'hairy' edge of oscillation which would 
make the frequency unstable.  The voltage at TP1 should remain between 
1.7 and 3.0 volts.

73,
Don W3FPR

On 1/25/2013 3:40 AM, Ian Greenshields wrote:
> The LO on my XV432 transverter seems to be very unstable. I think it's
> something more than just temperature drift as the frequency will sometimes
> jump by several kHz. It's almost as if the crystal is hunting between
> different modes of oscillation.
>
> Prodding & wiggling the components in the LO circuit doesn't point to any
> obvious poor connection, although the crystal itself is sensitive to being
> touched, or heated by a finger. The LO alignment voltage at TP1 peaks at
> about 3.3V.
>
> I don't have the temperature oven for the crystal, although I think it's a
> requirement. But I'm concerned about the frequency jumping and a frequency
> drift of almost 10kHz which I would not expect even of a non-temperature
> controlled crystal oscillator.
>
> Any thoughts or pointers as to what could be wrong?
>
> TIA, Ian G4FSU
>