Quote:
Originally Posted by SteveCG
G8HQP_Dave: Yes, there is more noise than thermal at 100 Mc/s and lower. It is cosmic noise emanating mainly from our Galaxy - At 100 Mc/s typically it is about 1000 deg Absolute reaching as high as 10,000 deg Absolute towards the Galactic centre, with higher values at lower VHF frequencies.
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Here are some charts showing atmospheric and cosmic noise distributions. They are from a 1955 paper on TV tuners, but I don’t think that the universe has changed all that much in the intervening time.
Cheers,