Satellite receiver threshold

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satdish
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Satellite receiver threshold

Post by satdish » Mon Sep 19, 2016 8:13 am

Here's a question for the technically inclined? With the different fta receivers does anyone know what the true receiver threshold is in db? There should be a list compiled. Is it different for different modulations such as QPSK, 8PSK, AND 16APSK or the same with them? Back in the day receiver manufactures published this spec. It would be good to know this when designing a link budget for your system and the signals your trying to receive.

I can tell this spec with my Cisco by looking at the advanced menu's and reading the db margin available. On the Cisco the threshold is different for different modulation type.
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Re: Satellite receiver threshold

Post by Glenn » Mon Sep 19, 2016 1:57 pm

Ah ha!

Someone finally asked. I have been afraid to ask because of all the arguing going on.

Personally; I have never been able to find any spec's in reference to your question. I always thought it was part of deciding upon purchasing a receiver. However; in my opinion, from stuff I have read, the FTA market is not particularly directed to technological genius's; so even if the information was publicized, what good would it be?

Obviously; the FTA market is quite competitive. I think that is pretty neat!

If I showed the specs' to my neighbor, the information you are referring to, it would be meaningless to him. All he would want is the picture on his TV! Think he is going to understand what I tell him? Nope! He just wants that picture!

I enjoy FTA because it is easy to hook up a system and sit back and enjoy TV from all over the world. Since the information you refer to, is not included in spec's, I go by what speeds can be decrypted, and the number of types of different modulation can be decrypted. That information is stated.

And ..actually...the most important part of any system is the antenna and feed; My opinion. That includes the quality of coax. My opinion. At such high frequency; the better the coax, the less loss of signal strength. Sort of is 'exponential', compared to hf frequencies. My opinion.

I just received my Cisco's several days ago, and they are in a different world! They do give the spec's but who is going to read them? The average consumer? I do not think so. The average consumer purchasing a subscription service? I don't think so! Mom and dad didn't when they had their Cband installation installed about thirty five years ago!! Kept drifting! They switched to cable, and gave the cband stuff to me, and I threw the receiver into the garbage can after realizing what was going on.

You pay for what you get. Unfortunately; they paid a lot of money, and still got the shaft.

Drift...the receiver was a piece of crap as matter of fact! Drifted all over the place!

The Cisco's are good quality. No doubt about that. But they are not designed for the average hobbyist. My opinion.

So; why all the arguing? In other words; who cares? They are no doubt more sensitive and stable, and have the ability to prevent RF interference from adjacent frequencies; etc.

When 'programmed'...they would be just fine. For FTA. I never hear anyone talk about that part. Just sit back and press the button on the remote! I never hear about that part. But the average consumer is not going to figure out how to program them very easily. I found that out myself. Put the Cisco in conjunction with an inexpensive FTA receiver that has the ability to scan, and you can do 'wonders'. I have no doubt about that. But that is a limited 'market'. For the very serious hobbyist; my opinion.

All you have to do is type in the LNB/LNBF configuration; the frequency; the symbol, and 'away you go'!

I don't think my neighbor is going to do that.
Maybe 'Rainier' will do that for you. I don't know.

Just thought I would put my 'two cents in'..will probably delete this post after I read it!! I do not want to see anyone arguing over such simple stuff.

Again; the Cisco's are high quality; compared to the inexpensive FTA receivers; or I would never have bought two of them! You do get what you pay for. I learned many years ago; if you want quality, you pay for it.

The video is 'super-great'... But I am nearly 70 years old! It is nice to have even a few subscription channels on Cband. So keep it up guys! Hope you get more! If not, we have FTA here on inexpensive receivers!

Oh..by the way; I just bought a brand new FTA $100 receiver for my wife to use. In conjunction; with the Cisco receivers that are being used for subscription service. The spec's looked good to me. Did not have a 'squelch' control on it though!! :lol: :lol:

Respectfully,
Glenn

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Re: Satellite receiver threshold

Post by satdish » Mon Sep 19, 2016 3:01 pm

You bring up some good points. What I was getting at is if you want your system to work well you need to have adequate signal under all conditions. I usually like to run a 5 to 6 db margin when designing my link budget. Yes the Cisco's have the tools meant for commercial installations and they can be used to maximize your system without needing external meters, I like that. Most FTA boxes have a exaggerated quality meter and that's it. People who are in the hobby need to realize how to set up a system properly or they're just shooting in the dark.

I have read on other forums when people can't get a signal they start cranking wrenches without understanding what they're doing. They then complain when they throw the whole system out of whack. IMHO you need to know what your doing or you pay someone to do it properly for you. It makes life much easier. :grin:
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Re: Satellite receiver threshold

Post by fatso » Tue Sep 20, 2016 8:23 pm

satdish wrote:Here's a question for the technically inclined? With the different fta receivers does anyone know what the true receiver threshold is in db? There should be a list compiled. Is it different for different modulations such as QPSK, 8PSK, AND 16APSK or the same with them?
It varies from tuner to tuner, as well as modulation type. It also varies with FEC rate too. For most commonly encountered signals, minimum noise margin is:

QPSK-3/4 = 5.5 dB
8PSK-5/6 = 9.4dB
16APSK-5/6 = 11dB
32APSK-5/6 = 13dB

If you got a super duper low noise tuner, then your numbers will be a fraction smaller. If you got a cheapy tuner, then slightly higher. I have tested many receivers over the years and some do incorporate more sensitive tuners that will lock signals on the verge of threshold.
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Re: Satellite receiver threshold

Post by satdish » Wed Sep 21, 2016 8:10 am

fatso wrote:
It varies... as well as modulation type. It also varies with FEC rate too.
That is correct, a 3/4 (FEC) error correction will work with less signal than say a 7/8 or 9/10. Higher SR, 30k vs 15k is also harder to deal with due to increased data. It's not the old 6db analog threshold expansion system like Uniden offered. :smile:
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Re: Satellite receiver threshold

Post by Global Mike » Fri Sep 30, 2016 2:32 pm

Another angle is what is minimum dB level to break threshold on a Star Choice/Shaw Direct receiver,
which uses the Digicipher 2 system. Older regular receivers mute out below a +2.0 dB C/N level.
The newer DSR-600 series receivers, which would be akin to an FTA receiver with DVB/S2 capabilities, demand a level of at least +5.5 dB to break threshold when used to receive MPEG-4 signals commonly used for HD transponders. It is all down to numbers and total gain required in your system.
In this case, switch from MPEG-2 Digicipher to MPEG-4 version costs another 3.5 dB.
That is a lot of difference in raw materials when dealing with small Ku-band systems.

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Re: Satellite receiver threshold

Post by satdish » Sat Oct 01, 2016 8:08 am

Global Mike wrote:Another angle is what is minimum dB level to break threshold on a Star Choice/Shaw Direct receiver,
which uses the Digicipher 2 system. Older regular receivers mute out below a +2.0 dB C/N level.
The newer DSR-600 series receivers, which would be akin to an FTA receiver with DVB/S2 capabilities, demand a level of at least +5.5 dB to break threshold when used to receive MPEG-4 signals commonly used for HD transponders. It is all down to numbers and total gain required in your system.
In this case, switch from MPEG-2 Digicipher to MPEG-4 version costs another 3.5 dB.
That is a lot of difference in raw materials when dealing with small Ku-band systems.
Shaws 8PSK signals go out sooner than the QPSK that the nature of the beast. I think a DSR 600 could be used for FTA DC-2 8PSK signals if the FW was modified and you could write SR FEC etc to it. 8PSK falls off the digital cliff at about +5.3 dB from what I've observed on a G1 signal.
I am too cheap to pay for a banner slot to hawk my products so I spam this board instead. I am intolerant of the c band community, so I belittle them under different aliases. I post fake news on the guitar man's website. Now I am no longer welcome here.

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