Multiple LNB deterioration

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jkbrennan

7 posts

Wannabe Geek

Topic # 94882 20-Dec-2011 21:00

I have a Strongs SRT 4661X satellite recorder set up by an experienced installer in April 2010. In addition to Freeview he tuned up the SBS channels which I make regular use of. The signal strength of the SBS channels proved marginal so he came back in June 2010 and changed the type of LNB for a stronger/larger (?) one. That gave us steady SBS reception for about a year, but I started to notice a gradual deterioration and last month lost SBS altogether. He came back and got back up on the roof and replaced the LNB. The Sat receiver reported 76% for SBS and continued good performance for about 5 days even in rain. And then there was a sudden drop (down to 60-64%) which in a clear sky is slightly better than marginal (56-60%) .

The installer thinks the cause of the LNB deterioration might be the current coming from the Sat receiver. I had a bit of rough run with the receiver from new – pressing the EPG button would intermittently cause the receiver to restart. After 3 trips to the service centre it came back with a new motherboard finally fixed as far I could tell.

I am considering passing the receiver to a relative in another city , but am concerned that this sort of deteriorating LNB behaviour could lead to loss of even Freeview within a relatively short time.

If there is some who could cast some light on this frustrating state of affairs I would most grateful.

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256 posts

Ultimate Geek
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Reply # 560131 21-Dec-2011 07:11

SBS has been down in power for some time now, try measuring the voltage output from the STB, should be round 13v for SBS and 18v for freeview

Jaxson

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Reply # 560134 21-Dec-2011 07:46

Could be cable joints deteriorating, or alignment not ideal. Hopefully your professional would have checked for these things.

Plan B
These are known to be pretty good
Basic, but have the freeview guide etc.

vexxxboy

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Reply # 560135 21-Dec-2011 07:52

i have sky and in the past year have had the LNB replaced twice and after talking to the sky technician he told me that was due to the latest shipment of LNB's, and in his words, "they were a crap shipment" and he couldn't guarantee how long the new one would last, he said maybe a week or a year, but hes replacing them regularly and he is waiting for a new shipment to fix the problem.

Common sense is not as common as you think.

jkbrennan

7 posts

Wannabe Geek

Reply # 560447 21-Dec-2011 21:41

Thanks for your replies.

Injuised, I don’t have the wherewithal to measure these voltages, but the serviceman did have and he spent some time studying the results from his equipment because he really didn’t want to go back up our steep tiled roof.
As we were getting v good reception after he came back down from the roof about 3 weeks ago, I don’t think it is cable joints deteriorating Jaxson.
And yes Vexxxboy I do remember him talking about some very poor LNB units around, and that he wasn’ t putting one of those up top.

injuised

256 posts

Ultimate Geek
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Reply # 560452 21-Dec-2011 21:47

For good SBS at the power levels their running at the moment you need at least a 76CM dish and an LNB with good cross pol isolation

Printertech

75 posts

Master Geek
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Reply # 560806 22-Dec-2011 20:25

What is the best LNB to buy to get SBS with a 65cm Sky dish? I am using a 60cm dish with a bracket to get D1 and D@ at the moment, but SBS has gone.

dontpanic42

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Reply # 560821 22-Dec-2011 21:44

Printertech: What is the best LNB to buy to get SBS with a 65cm Sky dish? I am using a 60cm dish with a bracket to get D1 and D@ at the moment, but SBS has gone.

Are you using both the D1 and D2 LNB on the same coax cable?

I installed a 65cm satellite dish for someone a couple of days ago and it gets SBS just fine... around 70% signal strength and quality.

I used one of these and these.

Printertech

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Master Geek
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Reply # 560916 23-Dec-2011 10:30

dontpanic42:
Printertech: What is the best LNB to buy to get SBS with a 65cm Sky dish? I am using a 60cm dish with a bracket to get D1 and D@ at the moment, but SBS has gone.

Are you using both the D1 and D2 LNB on the same coax cable?

I installed a 65cm satellite dish for someone a couple of days ago and it gets SBS just fine... around 70% signal strength and quality.

I used one of these and these.

My dish is the same. I have dual LNBs switched at the dish and feed down one cable. I have tried realigning with meter and SBS is maximum, but still not enough signal. I will try swapping the D1 and D2 LNB, then buy a new one if necessary.

openmedia

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Reply # 560926 23-Dec-2011 10:54

I had a bunch of LNBs fail on me a couple of years ago and the lifetime can vary dramatically from model to model. In general 5 years is a good period, but some better ones might last closer to 10.

Generally known online as OpenMedia, now working for Red Hat New Zealand as a Solution Architect for all things Linux, Virtual and of course Cloud. Still playing with MythTV and digital media on the side.

Printertech

75 posts

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Reply # 560933 23-Dec-2011 11:24

Are the Sharp ones better quality?

jkbrennan

7 posts

Wannabe Geek

Reply # 561069 23-Dec-2011 21:33

If I could return to my original post, I am no closer to having any confirmation as to why one LNB dramatically dropped its performance in just over a week, another in just over a year, and the one before that I think was also on a downward slide. Could it be the receiver?

dontpanic42

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Reply # 561082 23-Dec-2011 22:22

Sorry, things got a little OT there.

Just going to be completely obvious here and ask: have you checked that the LNB isn't going off skew?

jkbrennan

7 posts

Wannabe Geek

Reply # 561273 24-Dec-2011 20:31

By off skew, I take it you mean off alignment.

The installer has since told me that he has done in excess of 16000 installations. He had the gear and I’m sure he left everything tight – he’d rather avoid having to get back up on our roof if at all possible. But he has never seen otherwise reliable LNB’s deteriorate so quickly at the one location.

dontpanic42

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Reply # 561286 24-Dec-2011 21:47

That's why I said it was a completely obvious question. It doesn't sound like the LNB skew, but it's always worth putting those simple questions out there first, just in-case. :)

Similar to what the installer suggested about current etc... if it is the receiver, maybe the receiver is outputting too high a voltage when outputting 18V for the horizontal polarity.
I've never come across that myself, but logic would say that if the LNB is receiving too much voltage, it's possible that could be causing a gradual degradation over time.
I don't know enough about the electronics inside LNBs, but there's the possibility that that might be the cause.

Do you have a multimeter you could chuck on the LNB input on the back of the receiver to check this?

grolschie

597 posts

Ultimate Geek
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Reply # 561409 25-Dec-2011 17:30

jkbrennan: By off skew, I take it you mean off alignment.

The dish can be perfectly aligned and the skew out. The skew is the rotation of the LNB in it's holder.

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