Re: #LimeSDR Transmit Anomaly #limesdr

Siegfried Jackstien

he see wobble also with no beacon lock ... (but then additional drifting)

please please ... do NOT use offset ... if there IS a spur ... you see it in your own if display (next to your passband) and you just do another tx calibrate (and spur should be gone or a lot lower) ... if you use offset ... then you may send the spur without notice (but may disturb on anotherones frequency) ... so best is to set that to 0hz ... and in case you see your own spur do a tx calibrate (do NOT FORGET TO SWITCH OFF AMP!!) ...

jose also measured how clean (or not) the lime is with different levels ... and he also wrote to stay 10 db or more below max power (and use another lna in the chain) ... in that level range gain is cheap :-) ... i use a skyworks65017 for around 20 db gain from 0.1 to 6 gig ... VERY nice broadband amp for a few mw out

first pic is jose

secondand third is my pluto ... first half with beacon lock on and second half beacon lock off

lnb is only tcxo modded and tcxo is INSIDE lnb but we have almost stable temp outside (cloudy and only a tiny bit of wind) so lnb drift is low

spectrum set to x8 resolution and 20 lines/sec on waterfall speed in first and 10 lines/sec on second picture

compare that with what jose sees ... his signal wobbles a lot more even if i do not count the maximum swings (100hz) but only the mean swings up and down (say 30 hz or so) ...

so all lime and maybe also pluto users ... please post a screenshot ... resolution x8 .. 10 to 20 lines wf speed and max zoom ... so we can compare the results (internal and external reference welcome)

joe ... may you also do the same test and post a screenshot??

greetz sigi dg9bfc

Am 30.05.2020 um 15:36 schrieb josephlevy via

Hi Jose and Sigi
I can relate my experience with the LimeSdr USB

Do not transmit anything near the max power out.(signal is way distorted  then)
I set it to -20Dbm  (so needed another amplifier in the chain to reach the 2.4 Ghz for the Qo100)
But then it does not get stuck, no central spur (I use 250 khz offset) and see no spur anywhere on the full band of the Qo100)  (peak signal when modulating with a single tone S9+12
and nearly 37-8 S/N).
BTW   Jose I use now the X8 resolution on the waterfall and then you can see very accurately any Jitter in your signal, and mine is very similar to the band edge Beacon. If the 'lock to Beacon' is wobbling (a bit, not complete unlock) the you'll have wobbling on your TX freq.)

De Joe 4X1RV

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