[SADXA] Frequency Measurement Test

[Darrel]

Thanks for the info, Wes.
    Years ago, I used to monitor WWV and WWVH on 10 MHz for days at a 
time, with a high resolution (about 100 mHz) slow waterfall display.  
You could see the traces from the two stations separate, as they 
suffered Doppler shifts from the ionosphere at different times of day, 
corresponding to their different sunrise and sunset times.  It's 
interesting that you were achieving such better results when you avoided 
sunrise and sunset too.

    Again, very well done with your results.

              Cheers,
                     Darrel, aa7fv.

On 8/16/2020 2:46 PM, Wes wrote:
> I was going to write a detailed report on my method, but didn't want 
> to bore folks.  So in a nutshell, I use GPS derived signals to 
> downconvert the unknown to an audio frequency (~600 Hz).
>
> Then I rely on Spectrum Lab software's remarkable ability to 
> interpolate FFT bins even on a noisy signal that is spread in 
> frequency and amplitude.  I juggle the FFT window time (length) and 
> sample rate to trade off acquisition time and FFT bin size. Of course 
> longer and narrower have better resolution but on noisy signals it's 
> pointless. Generally, I was using about 16 sec and 60 mHz bins. Quite 
> frankly, I'm astounded that I'm coming up with numbers that are so 
> good, considering the signals involved.
>
> As to your real questions about Doppler. etc. I can't really overcome 
> it so I live with it and report what I measured.  Either my results 
> have serendipitous bias in the right direction or the Doppler was "in 
> the noise" no pun intended.  My 20-meter daytime results were an order 
> of magnitude more accurate than the 40 and 80-meter ones from near 
> sunset times.  In some cases, I averaged the averages.
>
> Since I recorded the signals, I can revisit them if I become so 
> motivated.
>
> Wes  N7WS
>
>
>
> On 8/15/2020 8:20 AM, Darrel Emerson wrote:
>> Congratulations, Wes!
>>    I'm impressed that you were able to overcome some of the 
>> ionospheric Doppler shift.  For how long did you average measurements 
>> to get your final results?  Any other tricks to reduce the impact of 
>> the ionosphere?
>>
>>        Cheers,
>>                 Darrel, aa7fv.
>>
>>
>> On 8/15/2020 8:03 AM, Wes wrote:
>>> There are two "official" ARRL FMTs per year, but we frequency nuts 
>>> clamor for more.  Hence Connie, K5CM, the reference station, has 
>>> been doing unoffical ones more frequently.
>>>
>>> The last one was Thursday (MST) afternoon and evening.  I thought 
>>> the bands were awful and even disconnected antennas between the two 
>>> 80-meter runs because of lightning concerns. Nevertheless, the 
>>> results were posted this morning 
>>> (http://k5cm.com/aug%2013%202020%20fmt.htm) and I did quite well, 
>>> coming in fifth in the parts-per-million metric.
>>>
>>> Wes  N7WS
>>>
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>