FEC on Sat-Stream

[marian321]

Re: FEC on Sat-Stream

SK* IT uses a peculiar combination of FEC and symbol rate (5/6 and 29900) to stuff more channels inside transponders.

This is a critical combination.
But on 0,8 west they often use 28000 - 7/8 and on 23,5 east they even use 27500 - 9/10 or 5/6 in 8PSK. This requires good LNBs, big dishes and not too bad weather.

[Fireflyer]

Re: FEC on Sat-Stream

What is the critical combination for a receiver?.

[marian321]

Re: FEC on Sat-Stream

Ohh, this depends on several factors:

- Dish (size and correct position)
- LNB-quality
- Cable (length and quality)
- plugs
- diseqc switches, splitters...

and at last your receiver. If everything is ok, even 9/10 can be received with a 60cm Dish at 48db (but then without diseqc or in the middle).
But on heavy rain I think then you lose signal.

[herrr]

Re: FEC on Sat-Stream

But on heavy rain I think then you lose signal.

That's what we said before.
In terrestrial broadcasting, of course, dangers of damaging signals are even worse and different... (actually I'm more expert in terrestrial communications )
(I used to be a professional in radio broadcasting for 25 years ...)

[marian321]

Re: FEC on Sat-Stream

Fireflyer asked for the critical combination for FEC. In Germany 5/6 makes no Problems on 19,2° East.
OK, DVT-T is more critical on weak signals.
I adjust dishes on this "critical" Transponders. Thats important if you use multifeed on one dish! If these transponders are ok, the other have no problem all.

[herrr]

Re: FEC on Sat-Stream

Fireflyer asked for the critical combination for FEC. In Germany 5/6 makes no Problems on 19,2° East.
OK, DVT-T is more critical on weak signals.
I adjust dishes on this "critical" Transponders. Thats important if you use multifeed on one dish! If these transponders are ok, the other have no problem all.

That's right!
The situation I've explained before for SK* IT began in past months, when symbol rate went to 29900

[Fireflyer]

Re: FEC on Sat-Stream

Why do you use critical transponders for adjusting your dish? And what transponders are this?

[marian321]

Re: FEC on Sat-Stream

I use e.g. 12480v or 12692h on 19,2° east or the 29.900 5/6 transponders on 13° East based on bad experience by other transponders.
When you take the "strong" transponders with high FEC rates (1/2 or 2/3), it can happen that you fix the dish not exactly enough for the "weak" or critical transponders. And the next day the adjusting starts again.

[herrr]

Re: FEC on Sat-Stream

Why do you use critical transponders for adjusting your dish? And what transponders are this?

marian will tell you the transponders to follow for a good adjusting.
But the reason why is really easy to tell...
Strong signals are so good that they work very well even if adjusting is not micrometrically right...
But if you follow weak signals...
It was that way since first yagi antennas in first TV broadcasts 70 years ago: if you have to point a place, where two or more TX are placed...follow the weakest one...

Edit: sorry... he was already arrived, I was in writing...

[Mobley3]

Re: FEC on Sat-Stream

The moral of the story is quite simple. Once you have located the Satellite you wish to receive, use a weak transponder to peak the dish for that satellite, result no rain fade or drop-off of signals.

Regards Mobley3

[Fireflyer]

All use the same procedures, the FEC - viterbi (extern) and Reed Solomon (intern with the Relation 188/204 as a second "FEC" for DVB-S signals).
This is a part of the receiver OS.
If not - no signal...

Is the "Reed Solomon" a part of the FEC (1/2, 3/4...)

Whats the meaning of this 188/204? Where does it come from?

[marian321]

No, Reed Solomon is a second sort of protection. If you want to calculate the complete amount of the protection part:

P = (1 - FEC) + (FEC * (1 -(188 / 204))

e. g.

FEC is 1/2 ; P = 0,5392 %

This means 53,92% are protection, the rest (46,08%) is "usedata".

This means a hard protection.



In DVB-S the datas are sent in Blocks with 204 Bytes. 16 Bytes are for correction parameters (Reed Solomon) and the rest (188 Bytes) are normal datas. This means 16/204 is for the "intern correction" (7,843%).

[runmo]

Re: FEC on Sat-Stream

case closed, enough detailed info has been given to explain the original question.