[R-390] 2nd xtal osc temp control

[Jacques Fortin]

Hi Larry, Perry, group,

I am sorry, but it is not as simple as that.
When Xtals are made to be used in an oven, the cut angle in the raw crystal
have to be selected to minimise the drift around the oven temperature, not
around the ambient or any other temperature.
If the R-390/390A crystals were originally made to have a "flat" temperature
characteristic around 75C, moving the oven operating point by re-calibrating
the thermostat may not yield to the best results...

73, Jacques, VE2JFE


Perry, Good point on the temperature of the ovens and I agree with you.  I
found an ovenaire 55 degree 2 crystal plug in one that I'm using, but I
don't see how to adjust the 2nd osc temp.  How is that done?

Regards, Larry

On Fri, Nov 1, 2019 at 10:23 PM Perry Sandeen via R-390 <
r-390 at mailman.qth.net> wrote:

> Yo Bubba Dudes!,
> The thermostats used for the VFO and 2nd xtal osc circuits are 
> commercial ones that can be adjusted over quite a wide range.  75C is 
> 167F and is not good for longevity of any circuits.  Try adjusting it 
> down to a much lower temperature. All the xtal box needs is a 
> temperature just a bit higher that the receiver chassis gets during normal
operation for stability.
> If that doesn't work one could consider a simple thermistor 
> proportional heater circuit if your are a Heretic like me.
> Regards,
> Perrier