Hello,?

I am able to receive to my U3S located some 5 meters away on the balcony when transmitting WSPR. My receiver consists of SDR connected to loop antenna. When observing the spectral waterfalls from SDR and WSJT-X, I see U3S signal spread over like four peaks and smaller bumps around center frequency. And WSPR decodes from WSJT-X return 4 lines for each frame, with varying db. This does not seem correct to me. Also output power is small, I have had only one reception and that was 3 kms with PA at 12 V (3 BS170s) and simple wire antenna.?

I will post screenshots of spectra as I have better time. In ?the meantime, anybody have idea what could be wrong??

Tapio OH2EYY

I am able to receive to my U3S located some 5 meters away on the balcony when transmitting WSPR. My receiver consists of SDR connected to loop antenna. When observing the spectral waterfalls from SDR and WSJT-X, I see U3S signal spread over like four peaks and smaller bumps around center frequency. And WSPR decodes from WSJT-X return 4 lines for each frame, with varying db.

Tapio

Unless you are very careful this is normal.
To monitor your own transmissions you must ensure signal strengths at the RX are normal. Maybe both RX and TX into dummy loads will avoid RX overload, maybe not.
And, in any case you may well pick up low level spurious signals that are insignificant. If one is at +35dB then other negative ones will not matter.

This does not seem correct to me. Also output

power is small, I have had only one reception and that was 3 kms with PA at 12 V (3 BS170s) and simple wire antenna.

Have you set the TX bias?
What current does the U3S take in standby and TX?

73 Alan G4ZFQ

Hi Alan,

Thanks. I am still not convinced but I will post screenshots (waterfalls, spectra and WSJT-X decodes)?later. The difference between the peaks is smaller than that, but let's defer that to solid data from measures I will post. I would greatly appreciate your evaluation then.

I have set the PA bias by method of observing the peak signal level at SDR and BS170 temperature?(the other method?suggested by instructions). Currently the PA bias is set the "Hot" but not "Melting" :)

Thanks,

Tapio

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Tapio

I have set the PA bias by method of observing the peak signal level at SDR and BS170 temperature (the other method suggested by instructions). Currently the PA bias is set the "Hot" but not "Melting" :)

I believe the best way to set bias is to observe 12V PA current. Just a few mA increase.
And observe this current when the U3 transmits.

Please note that an overloaded RX can give very misleading results.
Are you sure you are on frequency? How do you calibrate?

It is very helpful to be able to estimate power output, a simple diode probe across a dummy load is a good tool. Just a 1 watt 50R resistor, diode and capacitor required.

73 Alan G4ZFQ

Usuly this problem comes with ripple on the powersupply, change ps or run it from a battery and see if you still have the problem

Try run both ,u3s/amp on battery, the signal multiple frequency come from u3s and not the amp

Looks like you have a NB On at the receiver. I suggest try with NB Off.

73,
Paul N1BUG

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Paul
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