Normal not to reach max levels?

dankargo

dankargo

Specialist Contributor
My Satellite Setup
90cm Motorised
My Location
Brentwood
Hi all,

So this is a question that i’ve been meaning to ask for a while, ever since I went motorised a few years ago. I have a 90cm dish but find that, even on the very strong sats like 13E and 19E, most of the time I‘ll never reach 99/100 SNR levels on channels. Currently on 13E this evening and most channels are around the 78-81% mark (Rai 1 HD as an example). RTPi was one of few that was above 90. on 28E however, I will almost always get 98-100% on the likes of BBC One HD/ITV HD. Is this just the result of a bad installation or normal? I don’t struggle with channels, locking satellites or get any picture break up - but its just something i’ve noticed since motorising my set up. It was the same in my previous property when I had my 80cm dish motorised.

Im using an Octagon SF8008 with OpenATV if that makes any difference :D
 
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Some transponders are so strong on DTH satellites that they may overload your satellite tuner with a large dish resulting in no signal.
 
This is a digital signal your working with, 100% on all channels is not needed anymore, this is not like the old analog satellite days when you needed every bit of signal you could get, I have great pictures and good sound at 40% on some very weak transponders at ether end on my arc.

And every thing you add to a system adds signal loss, 3 to 7 dB of signal loss can be almost 1/2 of your RF voltage on the system, cheap coax or coax not rated to 2 to 3 GHz can also add to the system loss.

The SNR readings are calculated by the receivers RSSI voltage from the tuner, and all tuners are not the same, you need special equipment to get the true SNR of a system.
 
dankargo said:
Im using an Octagon SF8008 with OpenATV if that makes any difference :D
Click to expand...
Let me solve your problem once and for all:
snrdb.jpg

And now let me ease your concerns.
You are simply a "victim" of comparing SNR signals in percentages between different tuners and receivers.
Take a minute to ask yourself what you are actually comparing, a percentage level of what exactly? Is there any globally accepted maximum value when it comes to signal that should represent that a digital signal maxes at 100%? These signals are subject to a ratio of useful signal compared to noise called Carrier to Noise or C/N. This produces a limitless value that is measured in dB. Professional tuners, such as the Silabs tuner you have on your SF8008 is more than capable of reproducing and measuring C/N in quite an actualized manner, so changing the value in the menu I show you above from percentages to dB will give you exactly what you actually receive in signal strength.
Usually anything above 14 or 15db when it comes to satellite reception is a significantly strong signal. So compare your signals in dB and you're good to go!
 
Hi
Does the number written as C/N Lock indicate the minimum signal strength (in decibels) to have a good picture?

This amount is only 3.1 dB for the frequency 11919, but it is 9.4 dB for the frequencies 11585, 12380 and 12558. Does this mean that to have a good picture for the three mentioned frequencies, the signal strength should not be less than 9.4 dB?

Thanks a lot

Screenshot_2023-12-04-16-31-17.jpegScreenshot_2023-12-04-16-34-08.jpegScreenshot_2023-12-04-16-32-17.jpegScreenshot_2023-12-04-16-33-24.jpeg
 
That's right. I think that not long ago I had the required min lock until now and this value was only 1db. I'm not exactly sure, but I think it was on the 14w belarushd channel. I didn't believe it and went to try where on the receiver I lose this frequency. and the information on Lyngsat was correct.This is the Locka information - for each frequency separately
 
Beli1910 said:
That's right. I think that not long ago I had the required min lock until now and this value was only 1db. I'm not exactly sure, but I think it was on the 14w belarushd channel. I didn't believe it and went to try where on the receiver I lose this frequency. and the information on Lyngsat was correct.This is the Locka information - for each frequency separately
Click to expand...

Indeed. I think it was 1TV America on 11W in C band. DVB-S with FEC of 1/2 is incredibly forgiving.

In fact, it's still there. It says 2.7dB but this is a little pessimistic.

1701771929349.png
 
The Chinese transponder at 10856V on 21.5°E only needs 1.0dB to lock:

FC25117E-FBC4-4FC6-B4F7-54FD46B93659.jpeg
 
Yes, quite a few of them can be found on satellites with a very low value of Lock.
 
ozumo said:
The Chinese transponder at 10856V on 21.5°E only needs 1.0dB to lock:

View attachment 153197
Click to expand...
that might not be a real C/N value. DVB-S2 specification extended SNR into negative range, -5dB or -8dB not sure of exact value and it all depends on uplink preset

i had channels dropping to 0% in the rain still tuned fine up to certain point when rain got heavy and lock disappeared

most transponders above europe will be lost during extreme weather conditions (Ku band), one exception is a very strong transponder at 5W (~20dB , few cm of heavy wet snow covered the dish and LNB, these channels were still good at 50% SNR
 
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