Re: Signal Drop

David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺

Ian and All,

As I thought (hoped) my TP 1 SNR was back up to 12.9 - 13.0 db by 17:00 UTC today.
It is currently 13.0 - 12.9 dB at 20:30 UTC.

Yes, the LNB does get baked in the sun at this time of year so I'm going to try to fashion an umbrella before dawn.

One thing I found was that the TV channels on Eurelsat 10 A and Eutelsat 9 did not show such a drastic change in SNR level.
In fact it was perhaps 0.3 dB at the most - same dish same LNB.

My EUMETCast TP 1 SNR has an overall change in level of 0.8 dB.

I suspect comparing TP 1 with a TV channel on 10-A is irrelevant anyway?


Most interesting comparisons, John. At lower signal levels I suspect there is a degree of confusion in that we talk of:

signal / noise

but what we are actually measuring is most likely

(signal + noise) / noise

so a change of signal at higher signal levels will result in a greater change in the measurement than at lower levels, where the value will tend to zero 0dB (and not go negative!). Noise isn't measured separately. So was the apparent level of the TV signal higher?

The graphs now clearly show that there was a dip seen by many stations between~14:30 and 15:10 UTC.

which may also have confused spot time level comparisons.

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