Measuring sun noise

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Measuring sun noise and comparing it to cold sky noise is a good way of evaluating your receive system perfomance.

Equipment needed

Probably easiest way to measure repeatable noise from Sun,Moon,Cold Sky or Ground is by using Spectraview in Continuum mode on an SDR-IQ or similar supported SDR. Any SDR that works with HDSDR with Spectravue thus gaining access to the excellent continuum mode.All you need to do is set the output mode in HDSDR as IF/IQ. Then select a virtual soundcard as the output and pick a sensible sample rate. This virtual soundcard may then be used as an IQ input for SpectraVue.

Using 190kHz Span and 0.5dB divisions you can measure to 0.1dB and a low FFT/BLK will allow fast response if the beam is narrow and the object moving - you can pan the dish and fit a full feed primary response onto the displayed field .

Record a screen shot and then send to the Group to compare results .No "s" meters /AVOs on the audio output or No1 ear lugs to add colour to the measurements .

Ground noise levels are the most variable on larger dish systems , so a "good" dummy load on the input 4 port WG switch is a better reference to have available .

Measurement technigue

Pan the dish etc across the object you want to measure and you will see the peak level - for Sun this is done against background "Cold Sky" noise floor reference level and needs the antenna to be moved to find the lowest value looking upwards and well away from Hot ground sources . Similar tests can be done using a known 50 Ohm load as the noise floor reference and used to measure gains and losses in a system .