When you switch analog FM radio or analog TV channel to non-existing station (in-between channels),- then you hear/watch just plain static noise. Question what I am interested is- what part exactly of such white noise is considered due to Cosmic Microwave Background afterglow ? Considering such spectral radiance of CMB

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Main peak of CMB radiation is elsewhere - in GHz territory, because CMB radiates like black body with temperature of $2.726 K$.
When considering FM radio static noise, approximate frequency band for about $100 \,\text{MHz}$. In such case from the graph can be seen that CMB spectral radiance intensity is on the order $10^{-20}$. I've seen some numbers on various sites that this noise part due to CMB is about 1%. This may correlate with such low intensity of CMB in FM radio frequencies. But I never found solid proofs of how this 1% was calculated. So, what is real part of static noise in analog FM/TV due to CMB radiation ? And preferably with explanation why it is so (or how value is calculated). Thanks.


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