need troubleshooting ideas for homebrew WSPR transmitter

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ND8I
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Joined: 2010/07/02 - 01:31
need troubleshooting ideas for homebrew WSPR transmitter

I'm trying my hand at designing a low power 30m WSPR transmitter using an Arduino ProMini computer and an Adafruit Si5351A oscillator. Timing is set using GPS. The output is boosted to ~200 mW using a BS-170 MOSFET followed by a low pass filter. I've built the unit, but can't get WSJT-X to decode any of the transmissions. I'm looking for troubleshooting tips.

I have a second 30m WSPR transmitter built around a Raspberry Pi that works just fine. I'm using it as a sanity check. WSJT-X decodes its signal, but not the new transmitter, even though they are running effectively next to each other.

Signal quality is reasonable (all harmonics at least 46 dB down). Transmissions start 1 sec after the 2 minute mark and go for ~110 sec. I used the encoding routine from the Raspberry Pi code (WsprryPi) in the Arduino code to generate the symbols (after changing int to long as necessary) and am getting the same symbols out of both the Raspberry Pi code and the Arduino code. I've mapped symbols 0-3 onto 0 Hz, 1.465 Hz, 2.930 Hz, 4.395 Hz which is added to the 10.140200 MHz base frequency. Is this correct?

I've included a screen shot of the waterfall and a list of the symbols generated if that helps.

Does any one have any suggestions for things to look at to track down why WSJT-X doesn't decode my transmitter? Does WSJT-X have a diagnostic output? I've noted that the decode cycle goes very quickly with the Arduino WSPR transmitter and significantly slower with the Raspberry Pi transmitter. Is there a log/data dump feature in WSJT-X that might explain what it doesn't like?

tia,
Bruce/ND8I