Re: Signal Drop



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.



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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Email: david-taylor@...
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-----Original Message-----
From: David J Taylor via <david-taylor@...>
Sent: Wed, 27 May 2020 7:01
Subject: Re: [MSG-1] Signal Drop

Ian and All,

As I thought (hoped) my TP 1 SNR was back up to 12.9 - 13.0 db by 17:00 UTC
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?


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