Re: HVS-1 data


Ernst and All,

I've just had a look at EUMETAT's TD 15 again - which gets regularly updated and now contains a quite a lot more interesting 'relevant information' regarding reception.
It's well worth reading again.

It refers to 'recommended dish size' several times - but they don't exactly do this.
The 'required dish size' actually depends on where you live in Europe as the transmitted power contour varies across Europe.
See pages 15 - 18 and 30 - 31.

And the attached rain fade effect maps start with a 90 cm dish for instance right up to a 4.5 m dish at the end of the document.

And I would say it's not only rain fade to take into account.
I have quite often seen considerable reduction in 'signal strength' - leading to reduced SNR and Link Margin from ice crystals in nearby thunder storms 'in line' with the satellite when it's not raining that hard in my location.

Another thing to be taken into account is rain drops on your LNB face which in my experience can reduce your SNR by up to, 1.5 dB or more.
I read in the EUMETCast Satellite Antenna Satellite Pointing Guide that they recommend the use of an LNB rain shield on dishes up to 1.2 m.

And of course accurate pointing and skew adjustment is essential.




first of all we are talking about SNR not signal strength.
I also hope you only loose UDP packets not packages.

My above equations say that HVS-reception begins with about SNR = 9.3 dB. This is not on/off, you still have missed and lost packets.
The EUMETSAT recommendation of minimum 4 dB LM means they propose SNR >= 13.3 dB which is indeed rather high. This might
be intended for National Meteorological Services and should still work in not too heavy rain. I doubt you have no missed packets with
SNR between 10.5 and 11.5 dB. But it certainly works as your LM is between 1.2 and 2.2 dB (not below 0 dB as the one of Terence).


-----Original Message-----
From: Ernst Lobsiger via <ernst.lobsiger@...>
Sent: Tue, 9 Nov 2021 18:14
Subject: Re: [MSG-1] HVS-1 data

On Tue, Nov 9, 2021 at 09:33 AM, T-Online wrote:
everywhere i read that it is necessary to have min 12db signal strength for the HVS-1 Service....
With my 80cm dish i have all the time between 10.5 and 11.5db signal strength. I don't have with this setup any lost packages. Just in strong rainy conditions i am losing some packages.


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