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pc transmitting ssb audio without input

JamesW7EY Member ✭✭
edited January 8 in SmartSDR for Windows

I noticed my Flex 6600 radio is transmitting audio on SSB, even when the pc mic is unplugged. I have PC device level set to just below max for max dynamic range and the mic preamp adjusted so that the audio level is clean without any clipping. With the mic unplugged and recording in Audacity it shows that there isn't any audio on the mic input. SmartSDR shows that I'm transmitting something. In full duplex mode listening to it there is definitely something being transmitted. With the mic plugged in I can talk and it sounds ok but I'm concerned about this noise that is being transmitted. This happens on both "pc" and "mic" input but not "line", "acc", or "bal". Any ideas on why this is happening?

Transmitted signal without a mic plugged in:

SmartSDR view. RXing on ant2 with not antenna attached and I'm transmitting at 1w on ant1:


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Yes, it is transmitting something, but that is a very weak signal. It is the background noise. Check out the graph on the right at -120db. That is below your noise floor.

    You will also notice that no RF is being transmitted.

    This is why a FlexRadio makes a very good piece of test equipment as well as it is so sensitive.

    tldr; the radio is working as designed

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