[Lowfer] R75 Frequency Accuracy

[Pat Bunn]

Thanks Dex

Mine drifts about 12 -15 Hz from cold start. It ends up about 11 H z high so I need to adjust the oscillator (I  assume it is adjustable).

Pat
N4LTA

Dexter McIntyre W4DEX <dexter.mc at gmail.com> wrote:

>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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