[Lowfer] R75 Frequency Accuracy

[Dexter McIntyre W4DEX]

For the past few years I have primarily used a R75 for LF reception.  I 
bought it new and it does not have the high stability option.   I did 
not buy the optional oscillator since I had planed to operate it from an 
external 30 MHz source.  But after tweaking it right on frequency 
shortly after getting it I have found it to be so accurate and stable 
that I have not made any effort toward adding the external reference 
modification.  From a cold start it will drift maybe ten Hz but 
stabilizes within less than an hour.  It stays powered all the time and 
is always within less than about 0.1 Hz accuracy.  That's over a range 
of maybe 10 degrees shack temperature.

Dex

pbunn at patbunn.com wrote:
>
> I have an older R75 that I bought 15 years ago and rarely used until 
> recently.
>
> I use it for LF work with a home brew RX up-converter and it has 
> worked well but frequency accuracy has been quite a bit off. I 
> attributed this to my up converter being a bit off and combined with 
> the R75 error combining to cause the problem.
>
> Recently I have added a Trimble Thunderbolt and have begun to find out 
> where the error is. My up-converter is now phase locked to the GPS 10 
> Mhz output and yet my receiver is still 8 Hz off .
>
> Is this more than might be expected from a typical R75 or normal. It 
> seems somewhat excessive to me. I plan to add W1VDs circuit to add GPS 
> control to the R75 but want to make sure that the R75 is not 
> excessively out of spec.
>
> The sound card was calibrated with a GPS disiplined 1KHz signal and 
> found to be within .1Hz using ARGO before calibration so the error is 
> not there.
>
> Any comments would be appreciated.
>
> Pat
> N4LTA
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