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Michael just to add to what Hans said.

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With hints from Hans I have been spending a lot of time trying to produce all ZEROS?for drift on my transmissions. It is a futile task.

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For example I can look at my 40m tx's on the WSPRNET data base and can see?a stretch where I have all zeros except from one or two of the same? receiving stations, can see stretches where I get a lot of -1 from many stations but then returns to all zeros.

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I really think that no matter what you do there are too many beyond your control things that can cause +/- drift reports.

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The one thing though that really helped me for my U3S QRSS and FSKCW and WSPR transmissions is the?advice Hans gave me on the use of the park mode.

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When I look at my stacked signal at say the W4HBK grabber it is a nice straight line across the stacked image grab...big improvement as before it would wander up and down a few Hz.

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As Hans suggested I would try setting park mode to 2 and the park mode frequency to 150,000,000 and have an extra 2 minutes at the end of your TX frame. So if you are transmitting on 4 bands your frame setting would be 10 minutes with perhaps your calibration at 20 seconds or something like that.

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Give it a try and see what happens.

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Vernon

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On 11/23/17 02:44 AM, "Hans Summers" <hans.summers@...> wrote:

Hi Michael

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I’ve been noticing the drift on my U3S during WSPRing, usually about 0 to -1 on 40m and 0 to -2 on 20m. I know the things that can be done to reduce the drift, but I never really minded the slight drift. But now I wonder, will 0 drift make it easier for the decoding software to decode a very weak WSPR signal, as opposed to a signal with -1 or -2 drift?

The WSPR decoder has some algorithms for compensating for drift in the range -4 to +4Hz during the course of the transmission. The compensation assumes a straight-line drift. The reported number is the average drift in 2 minutes. It doesn't give you information about the shape of the drift. If the drift is a straight line then I think the WSPR decoder won't be impacted by the drift - it should be just as easy to decode as a straight-line signal. This is from my limited study of the WSPR decoder but I am by no means an expert on how it works. If the signal is very weak then I expect the decoder would not so easily be able to measure the amount of drift, which may make it harder to compensate for.?

Additionally, there are other forms of drift other than the transmitter. Specifically, the receiving stations drift, and any drift from ionospheric changes (e.g. Doppler shift when the height of the reflecting layer changes). The WSPR decoder is presented with the summation of these drifts. So potentially if your transmitter has drift then if the other drifts (receiving station, ionosphere) are added on, it could take the total beyond the 4Hz that the WSPR decoder can manage.?

Overall, my guess is that drift does have some impact on the ability of the decoding software to decode very weak WSPR signals, but I guess if the drift is small (1 or 2Hz) then the impact is rather minimal. To avoid taking any chances I think it would be best to try to implement the simple measures to reduce drift, if possible! See?

73 Hans G0UPL

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