Advice Needed Dying LNB?

[euro_sat]

Hi all, just wondered if anybody can help. I've recently bought a satellite PCI card for my computer, and have been playing with the spectrum analyzer/blind scan in DVB Dream. Using this, I've noticed that I'm not getting any signal on the high vertical band of my quad Inverto Black LNB.

Initially I thought that it was a problem with the card/drivers - but after testing signals on an actual satellite receiever too, I'm also seeing that there's barely any signal on anything high+vertical. In fact, only a couple of TP's on 13E come through on that part of the band!!

I understand that LNB's can blow (and it's possible that I may have shorted it with a loose connection or something) - but would it cause ALL of the 4 outputs to fail at that band? I though that a quad LNB was essentially like having 4 seperate ones?

I'm not sure how long it's been like this for (as I only tend to use that particular satellite dish to pick up feeds, which are usually low band), but anybody know what's could of caused it, and if there's a way to fix?

Here's the shots of the spectrum analyzer
7E: Imgur: The most awesome images on the Internet
13E: Imgur: The most awesome images on the Internet

 

[rolfw]

That's probably the most common fault I've experienced on LNBs, very rarely do they fail completely, and the high band, 22khz switched seems to be more susceptible.

Stopped using MTI quads some years ago, after having to replace several in a relatively short period for exactly this fault.






Edited.

 

[euro_sat]

Ok, thanks for the info. Guess I'll have to order a new one then! :/
That's interesting to know that the fault can affect all of the outputs, though. One of the reasons I originally bought the quad, was that I thought the other outputs could be used as a backup should one fail... Guess that's not the case.

 

[Terryl]

How many milliamps DC is your card rated for???

You might be a bit low on DC current to the LNB,(or have a coax problem) thus you not getting enough juice for the LNB to operate correctly on the higher frequency TP's.

If you have a standard FTA receiver can you try it on the #1 port on the LNB,(the DC power input) if it works fine then try the #2 port on the LNB to your satellite card.(with the FTA receiver on line)

 

[euro_sat]

How many milliamps DC is your card rated for???

You might be a bit low on DC current to the LNB,(or have a coax problem) thus you not getting enough juice for the LNB to operate correctly on the higher frequency TP's.

If you have a standard FTA receiver can you try it on the #1 port on the LNB,(the DC power input) if it works fine then try the #2 port on the LNB to your satellite card.(with the FTA receiver on line)

I've not actually checked - but it's a DVBSky S950 PCIe card that takes a 6 pin power from the power supply (via a SATA converter cable). I suppose that could be a possibility (and great if it's an easy fix like that!) - but I'm not sure that would explain why I'm still not receiving that band when I tried it through an old Technomate receiver too? I'm away next week - but will try a bit more experimentation when I'm back. Hopefully it won't fully self-destruct, as I need to remotely login and record some feeds while I'm away!

 

[Terryl]

Not enough DC current is one part of the possible problem, your LNB is using about 120 mA, but with your problem it could be that the LNB has gone bad as you suspect.

However it needs to switch to 11 to 14 volts DC for vertical transponders and the 22 Khz switching for that band needs to be set right, (ether on or off I don't see what does what in the tech spec's, maybe someone who has one can fill this part in) also the coax used should be rated out to 2.5 or 3 GHz(regular TV signal coax wont handle it) or you may be missing the high end transponders due to too much cable loss.

Here is a look at the band spec, it shows that the high frequency mode uses a higher band for the transponders LO output.
Technical specifications
Low band input frequency range 10.7 GHz ~ 11.7 GHz
Low band output frequency range 950 MHz ~ 1950 MHz
Low band LO frequency 9.75 GHz

High band input frequency range 11.7 GHz ~ 12.75 GHz
High band output frequency range 1100 ~ 2150 MHz
High band LO frequency 10.6 GHz

So if your coax cant handle the job at the high end then that could be the problem, look on the jacket of the coax, it may be marked as to the coax frequency response.

This also could be a corroded cable connector, or water in the coax, that would/could cause a drop out at the high end.

Also check your settings for that satellite, they should be, LO = 10.6 GHz, and the 22 KHz switching should be on? or off? (someone can fill this in) Diseqc switching should be 1.0, and the Diseqc switch port should be 1.