Re: #LimeSDR Transmit Anomaly #limesdr


jose maria trueba
 

Hi Mike, Sigi and Joe,

Thanks for the 50ms hint, Mike. I will try it.

Sigi,
Your skyworks 20dB gain MMIC does look great. Mine is only 12dB gain, which means that I need to use 8dB more power from LimeMini than if I would replace my MMIC with the one that you've got.
I have three amplifiers after LimeMini, 12+21+17=50dB gain in all, so I need -10dBm from Lime to get 10w output power and -7dBm from LimeMini for my regular PEP which is around 20w with final linear amplifier working at 14VDC (I get around 50w at 26VDC). 

My unmodified Lime Mini does have a strong jitter, but it gets better after several minutes. I have mot seen any otjer Lime Mini carefully. I wonder if other people can see such a strong jitter as mine.A very unacceptable jitter comparing with Sigi's Pluto with TCXO replaced, and Joe's Lime SDR using an external OCXO.
I did check what happened if beacon is unlocked and I saw no differences. I sent another picture with neacon unlocked and we could see the drift but jitter was as bad as with the beacon locked.
I will try an external reference in the future (I already have two SMA connectors ready for this purpose fitted at the rear panel).

I do not see the central spur if Lime power level is set normally, to any output level lower than 10dB below max power, but I can see it if I push TX power to -5dB. I agree with Sigi that is better to set TX offset to 0KHz so we can see easily what happens with the spur. By the way I do not see it exactly at the frequency where an AM carrier would be located but around 900Hz below that point. I had no idea why but it must be that I had my XIT set to +860Hz, that must be the reason why most probably.

I have talked with Sigi several times after our very first and very short QSO, the first day that I went on air through QO-100. He is a very enthusiastic ham and it is always a pleasure to talk with him.
Yesterday Joe and I met for our first time and we had a super.interesting and long QSO until we had to quit to have lunch. I learnt many things including that Israel time is only one hour ahead of central European time. Really it's a pleasure to meet so many nice and very interesting people.
This sat is really something!

73,
jose, ea2jx


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