Re: Signal Drop

David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺


Interesting comments.

A problem is, I'm not an RF engineer and I'm just reporting what my SR1 and SatPal meter are showing.
What it all means, is another matter :-)

Last year(?) Klaus Peter suggested I looked into 'atmospherics' effecting satellite signals which I did and I think I wrote a GEO article on my findings.
Of course the sun is very high in the northern hemisphere at the moment so I guess we should expect some 'turbulence?'

LNB umbrella is in place and the LNB is shaded from the sun and keeping cool at 09:00 UTC.
However, my dark grey 1 m dish gets hot enough to fry an egg - so that will be radiating 'thermal energy.'
I wonder if that is a factor?

I have a plan to temporarily deal with the dish warming - watch this space.

SR1 TP 1 SNR down from 13.0 dB last night to 12.6/5 dB at the moment with cool LNB.



First thoughts are that a hot dish means the LNB is looking at a warm source rather than the cold sky! Warm means more noise, poorer SNR, lower link margin. However, it depends on what the dish "looks" like at 11 GHz.

Perhaps that grey surface is fully reflective at that frequency, so the LNB is looking at a cold sky. I don't think it will be a perfect reflector, so some dish temperature rise will result in SNR loss.

The other effect is that the LNB will have at least /some/ "seeing" outside the disk of the dish, so a warm background is not desirable. Moving the LNB nearer the dish will result in "seeing" less outside the dish, but having a smaller capture area and hence get a smaller amount of signal.

Keep monitoring!

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