Society of Amateur Radio Astronomers: Hydrogen Line Reception by N4IP

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Hydrogen Line Reception at N4IP
by Pieter G. Ibelings, email pieter @ ibelings.com
and Moe Wheatley, email AE4JY @ bellsouth.net

We have been conducted tests on receiving the hydrogen line spectrum on a 4 foot dish using an Icom IC-R8500 receiver and our new homebrew spectrum analyzer hardware (further details pending once the circuitry is finalized). We now have a different digital filter that is flat. The passband on the R8500 is not all that great, but it allows us to see hydrogen with no problem. We are able to see it on the 4 foot dish after about 5 seconds of averaging. The Icom R8500 is tuned to 1420.406 and the 10.7 IF goes to the analyzer. The spectrum out of the R8500 is inverted so 10.6 MHz = 1420.506 etc. This test used a sample rate of 66.6 MHz and a decimated rate out of the processor of 1.282 MS/s in complex format. The output of the processor is 32 bit wide (16 bit I and Q data). The FFT size is 4096 which gives a resolution of about 300 Hz. The update speed is about 16 times a second so it is very fast.

The photos below show the station hardware, signals received, and an animated spectrogram of hydrogen from Cas A.

Click on thumbnails to download full-size image.

H1 animation

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