Measuring noise using the IC9700

No, I didn’t get on the moon on 6cm for the Apollo EME commemorative event. Chesty cold knocked me for six. Just recovering. Courtesy of our  vistors from Australia........l

It did allow me time to consider how I could make continuum noise measurements using the IC9700 (on 23cm) when it doesn’t have an IF output in the usual sense. One thought was to try and use the 12kHz IQ IF output, but I failed to find any information on this or how it could be used with existing SDR software. I know it can be done.

I had played with using my SDR-IQ at audio (it goes down to 500Hz) to measure noise power in a defined bandwidth using Spectravue running on the SDR-IQ. This worked well, but I was not happy with the amount of amplitude ‘jitter’ on the trace.

I managed to find  a working HP3400 true RMS voltmeter at Friedrishshafen, to do the same measurement with a ‘proper voltmeter’!. Again flicker, because of the nature of noise and the restricted bandwidth, made this unsatisfactory.

Finally, I set up the IC9700 as a soundcard input to Spectravue (no SDR-IQ) and selected continuum mode. With a moderate amount of FFT and smoothing the trace is as stable as it was using the SDR-IQ on the K3 8.215MHz IF output. Not only, but the results agree very well with those previous  IF measurements.

Now I CAN use the IC9700 for EME noise measurements!

Sam