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GM7HUD > DOPLER 05.03.06 11:49l 37 Lines 1312 Bytes #999 (0) @ EU
BID : A53480GM7HUD
Read: GUEST
Subj: Re: GB3VHF Rebuilt Beacon Accuracy
Path: DB0FHN<DB0RGB<DB0MRW<DB0WUE<DK0WUE<I0TVL<ON0AR<GB7ESX
Sent: 060305/0835z 01316@GB7ESX.#31.GBR.EU $:A53480GM7HUD [Witham, Esx]NNA V3.1
G0FTD wrote:-
>
> G8MNY wrote:-
>> This rebuilt beacon is SPOT on now,
>
> I'm not sure if I'm producing valid data from WSJT software but it's
> telling me that I'm getting a doppler frequency shift from GB3VHF upto
> +164Hz.
>
> The raw decode data is below for those that know better than me:-
>
> Sat Mar 4 23:44:00 2006
> ------------------------
We've got 3 things to determine frequency, GB3VHF, John's measurements and
your measurements.
John's measurements involve zero beating to accepted standards, TV carrier
frequencies so we can say that the TV carriers are correct. So we can
deduce that John's measurements of GB3VHF are correct too.
The discrepancy in your measurements will come from your receiver LO
accuracy, which in absolute terms you probably have measured and you'll
also so know its temperature drift etc.
So the only thing we don't know is how accurate the sample clock is in your
PC. It should be 11025kHz for WSJT IIRC, so I would suggest that the source
of the error is in your PC. Software normally has some kind of twiddly bit
to allow you to compensate for soundcard clock errors.
The clocks in my PC are annoyingly different for rx and tx. This means that
for a given mouse click in the tuning window, the rx and tx freqs are not
the same. Grrrr!
73 de Andy GM7HUD
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