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Re: zBitx +-2 MHz transmit spurs? --> SHOWSTOPPER for transmitting

 

I have yet measured the output voltage (after the 40 dB attenuator). Below are the results.
Indeed, one can see a 2 MHz amplitude modulation.


That's not an aliasing artifact. Below there is a picture with another time scale.



Yet another picture, taken from the battery connectors (with AC coupling of course)



So I don't see any 2 MHz component there, that could justify the AM modulation caused by the batteries resistance and varying current consumption. A? 14 MHz components is clearly visible.

73, Wojtek?

?r., 16 kwi 2025, 18:29 u?ytkownik Joerg DB2OO via <db2oo.ju=[email protected]> napisa?:
Frank,
?
my measurement setup has been described already in my FIRST posting on this topic:
?
"Measurement with a TinySA Ultra connected via 50dB (20dB + 30dB) attenuators.
Adding another 30dB of attenuation does not make a difference in the measurement result: The TinySA will then keep its internal attenuator at 0dB, but the spurs will still be -28dBc.
Reducing Drive to 50 will reduce the spurs to -31dBc."
?
BTW: using a TinySA instead of a TinySA Ultra provides exactly the same results.
?
I have built at least a dozen transceivers over the last years: none showed this kind of spurs.
?
To eliminate the voltage regulators U6 and U7 as the origin of the spurs, I added the missing 22uF tantalum capacitors on their outputs --> no difference, spurs are still there.
?
BTW:?the solution is not "shoot the messenger".
--
73, Joerg - DB2OO

Wojciech M. Zabo?otny
My GPG/PGP keys:
standard: 8192R/7E17F00A (B53C 1F09 BEA9 ED46 51B6 ?2C2E 4344 F292 7E17 F00A)
confidential: 16384R/1FEDB03C (3412 2330 E225 D57D 70C3 ?2340 B294 9408 1FED B03C)
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