[Lowfer] R75 Frequency Accuracy

[jrusgrove at comcast.net]

Same here. Have two R-75s that are used almost daily for LF/MF activities. Both have the TCXO option 
and remain within a tenth of the indicated frequency. Agree with John ... the shortcomings of the 
R-75 have been overstated. Both are used to receive LF and MF directly without upconversion. 
Performance in this application is on par with the the Harris RF-590 - the main LF/MF receiver - and 
other 'premium' receivers in use here.

Jay W1VD  WD2XNS  WE2XGR/2


----- Original Message ----- 
From: "John Andrews" <w1tag at charter.net>
To: "Discussion of the Lowfer (US, European, &amp;UK) and MedFer bands" <lowfer at mailman.qth.net>
Sent: Wednesday, January 23, 2013 7:59 PM
Subject: Re: [Lowfer] R75 Frequency Accuracy


> Pat,
>
> Like Dex, I keep the R75 on all the time, so the warm-up period is not a factor. I don't use an 
> upconverter, so I am receiving directly through the R75. The R75's shortcomings have been 
> overstated, but I really don't want to get into an argument over it. It has worked out very well 
> for me in all applications.
>
> Regarding calibration, it would be worth the time to take the top cover off, and adjust L2 in the 
> PLL unit. I would recommend doing that up at 10 MHz, since you now have a good source. You can do 
> this with Argo, assuming that you have done the sound card calibration first so that the only 
> error would be in receiver.
>
> At LF, my R75s are both within a couple of tenths of a Hz of being on frequency.
>
> John, W1TAG
>
> On 1/23/2013 6:37 PM, 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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