SDR as a TX monitor? - Maybe not

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Tony_AD0VC
Posts: 72
Joined: Sat Aug 08, 2020 2:38 pm

SDR as a TX monitor? - Maybe not

#1

Unread post by Tony_AD0VC »

I was on HF running FT8 and was noticing people struggle to copy me even when my signal was strong so I wanted to set up a monitor on my signals. At first I tried just running an AFEDRI with no antenna but I became convinced that the ugly signal was at least partially related to the AFEDRI. So I tried my Elad S2 with no antenna and also did not like the result even though it was different than the Afedri. So then I hooked up a -40db power tap from the TX with an additional 20db attenuator and hooked this to each SDR in turn. The results were:

AFEDRI:
afedri_40w_60dbatten.jpeg
ELAD:
s2_40W_60db_atten.jpeg
It looks like at least some of the spurs are coming from the SDR. The leftmost spur is real as it is the "suppressed" carrier from my TS450. Based on this experience, I am hesitant to use SDRs for signal quality monitoring.

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