Re: Over-Driven FT-8 QRM #FT8 QRM #FT8

Chuck K4RGN

I check my transmitted digital signals (FT8, etc) with a US$30 SDR USB dongle and SDRSharp freeware. The cheapest dongles don't receive below 25 MHz, but that doesn't matter. Put a dummy load on your transceiver, select 10 meters, send CQ's or VVV's in your chosen mode, and view your transmitted spectrum in SDRSharp. (This is a poor-man's spectrum analyzer.) Avoid overloading the dongle; if the dongle is close enough to your dummy load, you won't need to connect a whip antenna to the dongle.  

If you're splattering, it will be obvious in the SDRSharp waterfall display. With this setup a ham can easily adjust the audio levels between the computer and the transceiver to achieve a proper RF signal -- without having to wait for other hams to tell you that you're splattering. 

These SDR dongles are Swiss army knives for hams. I encourage everyone to get one, unless you have the luxury of a real spectrum analyzer in your shack. The dongles don't make calibrated measurements, but I seldom need calibration. Relative measurements are good enough. 

73, Chuck, K4RGN

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