17 replies to this topic

[dog-man]

Is it just me (perhaps dish mount moved) or is there a problem with the latest 2.1 build causing a lower signal quality?

On a VU, I think it is AGR???

Pictures are perfect, signal strength is normal but strangely quality can be as low as 10% and I would expect a bad picture if that was correct.

If it is only me then I have to get the ladder out and check my mount.





dog-man

[sat99user]

No, it's not only you!

I have the same on my Dreambox DM7000 ,
If i boot the latest pli (a june version i dont know with date) then i have a ber from about 50% , that can't be true!!

After booting an older pli or any other image i have the correct ber of 0%

So your dish has not moved you can ignore it.

[Erik Slagter]

BER, AGC, SNR, what are we talking about in fact?

Any AGC don't look at AGC, it's shows no information. Only SNR and BER are relevant.

[dog-man]

Sorry, I meant AGC.

It went abnormaly low after I did an 'automatic' scan on my vuduo+.

I didn't notice it being lower than normal prior to doing that scan.

Strangely, this morning it is back to where it should be.

I don't understand that as the weather was not bad.

A glitch?

The picture was perfect so just curious if something was wrong.


dog-man

[Erik Slagter]

As I said earlier, don't look at the AGC, it doesn't give you any information.

http://www.sat-unive...ad.php?t=218403

[dvboxer]

I noticed that on my vu+ duo some frequencies were slightly off after a service scan. so instead of 11222000 as it was advertised in satellites.xml it was in fact 11221750. Maybe that is the reason.

[dog-man]

But very strange that it did go very low on all channels but this morning is back to normal.

I will ignore it from now on whatever it reads.


dog-man

[Erik Slagter]

I noticed that on my vu+ duo some frequencies were slightly off after a service scan. so instead of 11222000 as it was advertised in satellites.xml it was in fact 11221750. Maybe that is the reason.

No that does not make any difference, the tuner will search and find the strongest frequency automatically.

[Erik Slagter]

I will ignore it from now on whatever it reads.

Yes, you can ignore the AGC reading altogether. The SNR value is important.

[dvboxer]

I noticed that on my vu+ duo some frequencies were slightly off after a service scan. so instead of 11222000 as it was advertised in satellites.xml it was in fact 11221750. Maybe that is the reason.

No that does not make any difference, the tuner will search and find the strongest frequency automatically.

But how come that the not exact frequency is stronger than the exact one? I can't imagine a frequency drift in the signal from the satellite. More probable to me seems a thermal dependency in the tuner (I quite often experience tuning problems when the box has just been switched on). And even if the tuner eventually tunes to the strongest frequency it will probably take some time to do so. It probably starts at the frequency given in the lamedb. And if that one isn't correct it takes time doesn't it?

[sat99user]

The frequency from the satellite is verry stable, it is your LNB that is drifting off (this is normal the Automatic Freuency Control of your box will corrit it).
If you use settings from internet it it can take some time to tune to the right frequency depending on how far your lnb is of from the one that scanned.

The problems you see when the box is just switched on is most likly to not stable power suply if power to lnb is not stable the frequency will be unstabele too.

Automatic Gain Control (AGC) is an indication how strong the the signal is from the lnb (if you have very long cable it will be low).
It has nothing to do with quality and as long as your box can amlify without los of snr it doesn't matter.
On my Humax 5400 I can make it 2.5% without errors.

[Erik Slagter]

@dvboxer: the tuner is very smart in finding the exact frequency quicky. It has to, because of the frequency drift of your LNB sat99user already told about. I have been experimenting with this and I can tell the tuner almost always finds the strongest frequency within one second, even if the requested frequency is way off. That is why, when frequencies are mentioned in lists, they are always rounded. It really doesn't matter.

[dvboxer]

Thank you both for the explanations

[dvboxer]

The frequency from the satellite is verry stable, it is your LNB that is drifting off (this is normal the Automatic Freuency Control of your box will corrit it).
...
The problems you see when the box is just switched on is most likly to not stable power suply if power to lnb is not stable the frequency will be unstabele too.

Let me ask what I can do about my startup problem as you seem to know a lot about that stuff. You see, the receiver is not directly connected to the two quad lnbs but via an 8/9 multiswitch with internal power supply which is located a few meters away from both the lnbs and the receiver in the basement of the house. The funny thing is my problem only occurs on one of the two satellites positions (19.2° and 28.2°) I use. That is only 19.2° is affected. This is configured as diseqc A and the other posittion as diseqc B. The equipment was installed by a professional team and if I remember correctly the 19.2 position was the main direction of the dish and the 28.2 position was off center. Therefore (and because the footstep of the 28.2 position is not made for Germany where I am), one would assume that 19.2 should be better receivable but it is the opposite. Furthermore, another receiver (technisat) connected to the same multiswitch doesn't have any problems at all. I also tried to use another output of the mulitswitch without success. Both tuners are equally affected. I should add that I used to have another receiver working at the very same location before I got my vu+ duo. This other receiver never had that kind of a problem (but many others which is why I replaced it). Also those tronsponders using 8PSK seem to be affected the most especially the ARD HD transponder which at times even after running for quite a while has periodic disturbances (Ruckler) once every 2 seconds I'd say.

Anyone any ideas?

Edited by dvboxer, 12 June 2012 - 12:39.

[Erik Slagter]

Almost definitely dish/lnb alignment, sorry to say the "professionals" have done a bad job here. There quite a difference between a "sufficient" alignment and "good" alignment. The first takes about a quarter of an hour, the second can takes hours, if you really want it perfect (like I do). Most external parties only do alignment of the dish itself, but do not take the individual lnb's (skew l/r, u/d and rotation) into account. That's the reason why reception on different lnb's can differ. There is also another possible cause for difference in reception between two lnbs, and that is a possible obstruction, thinks like trees, the roof top etc.

[dvboxer]

Almost definitely dish/lnb alignment, sorry to say the "professionals" have done a bad job here. There quite a difference between a "sufficient" alignment and "good" alignment.

Thanks for your explanation. You might be right but how does that account for the nonexistence of problems in the technisat (different "channels" on the multiswitch) and on my previous enigma2 box (on the same "channels"). This specificity to my vu+ duo makes me wonder whether there might be some software setup that is problematic. For instance I noticed that using diseqc protocol 1.1 leads to massively prolonged zapping time (2-3 seconds) when switching between 8psk and qpsk. However zapping qpsk<->qpsk even between different satellites is fast. The same holds for the simple setup. Only using diseqc 1.0 seems to be okay. But as there are quite a few setup options I am not sure I did everything correctly.

There is also another possible cause for difference in reception between two lnbs, and that is a possible obstruction, thinks like trees, the roof top etc.

That can be ruled out in my case.

[sat99user]

Hello dvboxer

you have a powered multiswitch that makes a powersuply fail unlikly (but not inpossible).
Powersuply fail is mostly on older boxes and replacing the secundary capisistors in the power suply will correct it.

In your case I would inspect the cables and connectors between multiswitch and your vu.

I do not know much about sat software so i hope you get help with it from others.

@ Eric Slagter,
If it is random you are right but dvboxer is saying it is only on startup and other boxes do not have the problem.

The time needed to a good alignment is depending on the tools you have , with professional tools it can be done verry fast les than an hour.

[jeffphil]

hi dvboxer as there seems to be some working and some not working stb's in your system I would simply swap the VU box with one of the other boxes if the fault stays with the VU then you know its internal to the VU or if the fault transfers to the other box then the fault is in the cabling or multiswitch.