Help with satelite reception technology?

SwissBuster · 18-09-2009

Somewhat of a newbie question here, but first the background.

I noticed a few months ago that I lost reception for the two Swiss-German TV channels. No great shakes, but I recently found out that I had also lost some nice radio channels, so I tried to re-scan for all these. I noticed in my research that the Swiss German TV channel was changed in March, probably coinciding with when I lost the images. My guess is they switched transponder and/or frequency. They are now being broadcast on 12399 H on Hotbird 13E.

I ran a scan on my system (homebuilt Media PC with Technosat Multytenne) yesterday and noticed that for this frequency, I get the message 'no signal detected' (or similar). Transponders/frequencies before and after this in the scan do pick up a signal. Also, I am receiving the other Swiss channels, broadcast on another transponder but on the same satelite and with the same encryption. Note that the Multytenne is a small dish but despite this the signal strength and quality is OK.

So, my question is both general and specific:
1. Can anyone explain how the frequency and transpoders work and what causes a poor or missing signal? A big question, I realise.
2. What can I do to recover these missing channels?

Thanks in advance.

**HB13DISH** · 18-09-2009

Originally Posted by SwissBuster

Somewhat of a newbie question here, but first the background.

I noticed a few months ago that I lost reception for the two Swiss-German TV channels. No great shakes, but I recently found out that I had also lost some nice radio channels, so I tried to re-scan for all these. I noticed in my research that the Swiss German TV channel was changed in March, probably coinciding with when I lost the images. My guess is they switched transponder and/or frequency. They are now being broadcast on 12399 H on Hotbird 13E.

I ran a scan on my system (homebuilt Media PC with Technosat Multytenne) yesterday and noticed that for this frequency, I get the message 'no signal detected' (or similar). Transponders/frequencies before and after this in the scan do pick up a signal. Also, I am receiving the other Swiss channels, broadcast on another transponder but on the same satelite and with the same encryption. Note that the Multytenne is a small dish but despite this the signal strength and quality is OK.

So, my question is both general and specific:
1. Can anyone explain how the frequency and transpoders work and what causes a poor or missing signal? A big question, I realise.
2. What can I do to recover these missing channels?

Thanks in advance.

What is the size of your dish in centimeters?
If it is too small then it is no wonder that you are having difficulty finding the channels.
Can you open any FTA channels on 12399H or the whole TP is not being locked on?
_http://www.lyngsat.com/hotbird.html
Can you see any of the channels on TP's above 12399H?
Perhaps your LNB is not setup correctly and also in your receiver.

SwissBuster · 18-09-2009

Originally Posted by HB13DISH

What is the size of your dish in centimeters?
If it is too small then it is no wonder that you are having difficulty finding the channels.
Can you open any FTA channels on 12399H or the whole TP is not being locked on? Can you see any of the channels on TP's above 12399H?
Perhaps your LNB is not setup correctly and also in your receiver.

The dish is about 45cm, but it is an eliptical and surprisingly efficient design. Before everyone says 'it's too small', I am receiving about 5000 channels and everything else I want from 28E, 23E, 19E and 13E without any problems. I ran another scan this afternoon to check the TPs on 13E - I have close to 100% signal quality and about 60-70% signal strength on the TPs I observed. The scan runs sequentially, first through V and then H. It picks up channels throughout the range for both. It regularly (about 10% of TPs) returns the message 'no signal' but I do have a signal for TPs both immediately before and immediately after 123999H.

For example, I picked up 22 channels from 12245H, failed on 123999H (no signal) and then picked up 27 from 12476H. I also picked up channels from 12265V and 124814V. Note that in both the H and V, the scan 'failed' for any TPs starting with 123 (about 5 or 6 in total).

So, is there a technical reason that this TP isn't working for me? What effects the reception of a TP?

Is there a way of finding out if these two TV channels did actually move TP back in March (for example, from Lyngsat)? This might help me understand why I 'lost' the channels.

**HB13DISH** · 18-09-2009

It is possible that this TP is not transmitting as much power as the other TPs.
Which means you might need a larger dish to receive all the channels included there or have a more sensitive receiver.

If you are not willing to change the dish, then you would need to optimize on the LNB, receiver and coaxial cable.
You could try
1 - Test with another receiver
2 - Test with a more sensitive LNB

***Tivù*** · 18-09-2009

I agree with the previous post: Whilst one might imagine all Transponders on a Satellite are likely to produce the same results at a fixed point on the ground, they just don't!

And with a dish that is relatively small, the difference between "go" and "no go" can be microscopic.

Digital Satellite reception has a miniscule "fuzzy" gap between lock and no lock and a small deviation in EIRP from one Transponder as compared to other co-located Transponders can make a big difference.

Basically, your small dish has insufficient margin to cope with such circumstances.

SwissBuster · 22-09-2009

Thanks to all. I guess when I have a spare moment I'll try some minute adjustments to the dish/LNB to see if this helps.

***Tivù*** · 22-09-2009

Good scheme - please let us know how it goes.

***Turok*** · 22-09-2009

high!
is the antenna installed,on the roof,or under the roof,with only 45 cm ,it should work,on sf1 and sf2 transponder,but there is not much signal in reverse,when its beginn to raining,your dish is to small 12 ghz transponders like srg 1+2 have are more affected then the others,because of the higher freqency!
my advice buy at least a 65 cm dish,when you cant install a bigger one,this is the size that i recomended!

SwissBuster · 22-09-2009

Originally Posted by Turok

Is the antenna installed,on the roof,or under the roof?

It is on the side of the house about 3 m above the ground: It is under the overhanging roof but a long way below it. THe view of the sky is unimpeded. You are right that I sometimes loose the signal due to rain. This has to be a very heavy storm, though. I usually loose 28E and 13E before 19E which suggests my dish is better aligned for that satelite. Unfortunately, I have not seen a larger dish for the Multyenne system.

Like I said, when I get a moment I'll play with the dish alingment. I suspect that it won't take much to get a signal.

SwissBuster · 25-09-2009

Originally Posted by Tivù

And with a dish that is relatively small, the difference between "go" and "no go" can be microscopic.

I tried adjusting the dish/LNB to improve the signal, cleaned the LNB, and even tried taping metal foil to the sides of the dish to see if this increased the reception. Nothing worked. Then I accidentally selected a Swiss German TV channel last night and it worked! Everything is back up. I can't explain this except that maybe the fiddling did make the miscroscopic change need to turn a 'no go' into a 'go'. Either that or the reception last night was minutely better...

It appears most channels I have are close to 100% signal quality and between 60-65% signal strength. Maybe this is at the threshold for a reliable signal?

***Tivù*** · 25-09-2009

Originally Posted by SwissBuster

It appears most channels I have are close to 100% signal quality and between 60-65% signal strength. Maybe this is at the threshold for a reliable signal?

I wonder if you had (still have?) a dodgy connection somewhere? The twiddling, prodding and poking may have disturbed it.

As regards Threshold, Quality figures are just not comparable with those from other systems - the metering characteristics of each box type are not consistent and they are affected by the rest of the system they're attached to as well.

Good for monitoring and for optimising the local system, but that's about it. So only you can really determine by observation what the threshold for lock is!

Oddly (or perhaps not), I find that on some Satellites the Quality threshold is much lower than for others - different Symbol Rates etc also seem to have an apparent influence.

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