Re: Tellicast


Ernst Lobsiger
 

On Sun, May 2, 2021 at 11:03 AM, Youssef Bennouna wrote:
Concerning the SNR, I think it’s less, usually around 9-9.5 according to the TBS interface.
Youssef,

with SNR 9.0 - 9.5dB you cannot receive HVS-1. EUMETSAT says you should have 4dB link margin (LM) for good reception.
LM depends on SNR and MODCOD used. I apply these formulas in my monitoring (also hard coded in Ayecka SR1 firmware).

Basic service:   MODCOD = 8PSK 3/5,  LM = SNR - 5.9 dB
HVS-1 service: MODCOD = 16APSK 2/3, LM = SNR - 9.3 dB

This shows you have around zero link margin for HVS-1. With my proposed SNR of 12dB you get LM = 12 - 9.3 = 2.7dB.
Not exactly 4dB as proposed by EUMETSAT but it will work with then and when HVS-1 UDP packets or even files lost.

Below is what I have with a 1.25m dish on a rather rainy day. HVS-1 reception is possible with a well aligned 0.85m dish.
Aligning a dish is an art in itself. A good start is using the sun for azimuth (a magnetic compass is no good). Also check:

https://www-cdn.eumetsat.int/files/2020-04/pdf_eumetcast_anten_point_guide.pdf


Regards,
Ernst








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