[R-390] 5 khz difference?

[Mark Huss]

Depends on the age of the crystal.  I have an R-390A with an origional 
(1956) 17 MHz crystal.  With an average aging rate of 5ppm a year on a 
50 year old crystal, 5 khz off is close to the specified aging rate.  In 
other words, if the unit was made before 1960, you are probibily talking 
about normal operation.  Younger than that, there is probibily a little 
contamination, increasing the frequency offset.  In my receiver, all the 
crystals are about 2 to 4 kHz low, except for three that were probibily 
replaced during it's life.

Masters Andy wrote:

>Good evening.  I have an EAC-67 series R-390A that I
>am working through and learning about R-390A's in the
>process. 
>
>Using a recently cal'd counter, I was able to set my
>BFO for top dead center on 455khz and it tracks +/- 3
>khz nicely as indicated by the ticks on the panel. I
>also adjusted the crystal calibrator by counting it on
>frequency at 200 khz.  It stays put rather nicely as
>well.
>
>Having done this, I then went through all the bands to
>have a look at dial calibration and have discovered
>that .5-8.0 mhz, the dial reads 5 khz low on each band
>but on the higher bands it is relatively dead on. (or
>it might be said it can be set dead on using the Zero
>Adjust for the lower freqs and is actually 5khz high
>on the higher ones).  In any event, what gives here
>and why the disparity? I first thought it might be my
>17 Mhz oscillator.  When I count the 17 mhz oscillator
>it indicates it is 4.790 khz low on all bands .5
>through 8 mhz.  After 8 mhz, it changes, but I can't
>get an accurate read on its error.  I don't see a way
>to "warp" the 17 mhz crystal on but I am not convinced
>that is the problem or that there is only one problem.
> Any suggestions?
>
>Thanks, 
>
>Dutch Masters NU5O
>
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