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Author Topic: Satellite Woes
Geoff Power
Film Handler

Posts: 37
From: Pershore, Worcs, UK
Registered: Apr 2012


 - posted 12-14-2012 06:19 AM      Profile for Geoff Power     Send New Private Message       Edit/Delete Post 
It was a bad night last night! [Frown]

Weather fine, signal OK at 75%. Screening the Nutcracker ballet live from Covent Garden, London, via Thor satellite and Technomate tuner to a full house. Terrible jittering and breakup seemed to happen on a 5-7 minute cycle, with corresponding signal strength fluctuation. Helpdesk replied that nobody else was complaining, but they managed to boost our signal to around 83%. During interval we re-aligned the dish by sending it off track and then bringing it back in - signal level rose to 85-88% (best we've ever had!). Reception better but still getting breakup every 10 minutes or so. Audience very understanding and no complaints (yet). Never had the problem before, and 2 test transmissions went OK, but one didn't - should've queried it at the time but decided it was "them"!

Any thoughts or ideas? Could a mobile phone cause it (hence the cyclical nature)? We're baffled [Confused]

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Randy Stankey
Film God

Posts: 6442
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 12-14-2012 10:09 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
I would start at the dish and work backward, checking all parts in the process.

Have you ever had the dish aligned by a technician using a signal analyzer, not just one of those little "bird dog" devices?
A bird dog just beeps or shows signal bars when you are lined up to the satellite. An analyzer actually shows your signal characteristics and can show you if your polarity or azimuth are slightly off where a bird dog won't.

Double check the dish support and mount to be sure nothing is loose. If the wind blows and makes the dish move or shimmy, that could cause the alignment to go off.

Check your dish to be sure that there is no snow or debris. Check your LNB to be sure it's properly tightened down and that there are no spider webs or dirt, etc.
Watch out for bee's nests! (Ask me how I know this! [Wink] )

Check wiring and connections to the dish/LNB. Make sure they are all secure with no cables flapping against the building. All connectors are secure. Did you use dielectric compound and weatherproof boots or tape on all connectors exposed to the weather? All connectors clean, properly crimped and tightened down? Don't forget grounding blocks.

Are there any splitters, switches or DisEQC devices in the lines?
(Little "splitters" that make it possible to use multiple LNBs on one dish, etc.) Check and replace anything that is faulty or suspect. Ensure that your receiver is properly programmed to recognize them if you use them.

Settings in the receiver: Polarity, freq., transponder, data rate & FEC. All of these have to be right or you won't get a signal. (90% of the time they will be right or you wouldn't get a signal at all but it pays to double check.)

Here is a trick I was taught about polarity settings on the LNB:
If the receiver is set to HORIZONTAL polarity it sends 12 volts to the LNB. If it set to VERTICAL polarity it sends 15 volts.
This is supposed to be how the receiver tells the LNB which polarity to use. It allows you to switch polarity from the receiver without having to go up to the roof to physically move the feed horn.
Some LNBs are single polarity and, in order to change polarity, you need to physically rotate them in the dish mount. However, these LNBs run on 15 volts, regardless of how they are twisted in the mount.

If you use a single polarity LNB which needs the 15 volts to power it but you bird uses HORIZONTAL polarity, the receiver might only be sending 12 volts. If your LNB is under voltage, it will work but won't be reliable.

The solution is to align your LNB correctly to the satellite but program your receiver to say VERTICAL polarity. This "little white lie" will cause the receiver to send the right voltage, allowing the LNB to work properly.

Before you do this, check with your satellite technician.
If you over-voltage your LNB, you could blow it up!

If you have done all these things and you still have trouble, I would suspect the receiver. Try swapping out or replacing the receiver.

Our set-up for the Met Opera uses two dishes and two receivers, hooked to the projector through a seamless switch to provide us with redundancy to circumvent such problems. If a problem occurs in one dish/receiver, I can switch to the other. Alternately, I can swap out components in order to troubleshoot.

If you are using a single dish/receiver, you won't have that flexibility.

If you consider your satellite programming to be "mission critical" I would suggest you have a dual/redundant system if you can, at all, afford it.

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Geoff Power
Film Handler

Posts: 37
From: Pershore, Worcs, UK
Registered: Apr 2012


 - posted 12-14-2012 11:36 AM      Profile for Geoff Power     Send New Private Message       Edit/Delete Post 
Many thanks for the comprehensive reply. We did most of the checks as suggested on the night, and weather was not an issue - no wind or rain, no foreign bodies or loose connections. The system was set up by a competent technician using a signal analyser, but probably needs a recheck. Admittedly one issue we have is that the setup info for this broadcast was extremely cryptic, and needed much interpretation - not in the format we recognise. But having got a good signal reading and a clean test broadcast we assumed all was well.

I'll pass the other suggestions up the line ...

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Randy Stankey
Film God

Posts: 6442
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 12-14-2012 01:32 PM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
I don't know what else to tell you. All that I know comes from experience, not specific training.

Is your dish motorized? (Is that what you meant by sending it off and bringing it back on?)

I can tell you that we looked into a motorized dish but decided against it because, no matter how carefully you set them up, there is no way you can know whether it is exactly on the bird or whether it is slightly misaligned. If you have a motorized dish, you should probably have its alignment checked.

As to settings, if you have the right bird and the dish is correctly aligned to it's location, the rest of the settings should be academic: Satellite frequency, transponder, polarity, data rate and FEC. As far as I understand, if you don't have those settings right, you just won't get a picture.

If everything else is right, the only thing left that I can think of is the receiver.

I have had receivers that seemed all right, one day, which just futzed out, all of a sudden, for no apparent reason.

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Geoff Power
Film Handler

Posts: 37
From: Pershore, Worcs, UK
Registered: Apr 2012


 - posted 12-14-2012 02:07 PM      Profile for Geoff Power     Send New Private Message       Edit/Delete Post 
Yes, our dish is motorised. My suspicion is heading towards the receiver - possibly a component overheating (which might explain why the test transmission ran fine for an hour before the live broadcast). The difficulty will be replicating the problem for the installation technician to see.

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Frank Cox
Film God

Posts: 2019
From: Melville Saskatchewan Canada
Registered: Apr 2011


 - posted 12-14-2012 02:34 PM      Profile for Frank Cox   Author's Homepage   Email Frank Cox   Send New Private Message       Edit/Delete Post 
If you think you have a marginal component that's overheating, put a hair dryer on it (briefly) while it's running and see what happens.

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Kevin Markwick
Film Handler

Posts: 43
From: Uckfield East Sussex England
Registered: Sep 2004


 - posted 12-14-2012 03:29 PM      Profile for Kevin Markwick   Author's Homepage   Email Kevin Markwick   Send New Private Message       Edit/Delete Post 
At the risk of teaching you to suck eggs..

Did you check the Pilot setting? Since the move to DVB S2 this has a habit of changing. It's caused us a few problems that weren't apparent on the test. Last night's Nutcracker was pilot OFF.

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Carsten Kurz
Film God

Posts: 3880
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 12-14-2012 06:36 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Operate two different receivers in parallel. That can easily rule out some issues.

No problem to operate two receivers from one LNB.

- Carsten

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Geoff Power
Film Handler

Posts: 37
From: Pershore, Worcs, UK
Registered: Apr 2012


 - posted 12-15-2012 05:59 AM      Profile for Geoff Power     Send New Private Message       Edit/Delete Post 
Thanks Kevin - good question about the Pilot Setting, and I don't know the answer! Like others, we've had no formal training - just pick it up as you go along, and hope for the best.

And yes Carsten, we do have a second receiver, but only one feed - the second box daisy-chains from the first and is only used for recording (which has never worked reliably, but that's a whole other topic!). Will enquire about running in a second feed.

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Mark Hajducki
Jedi Master Film Handler

Posts: 500
From: Edinburgh, UK
Registered: May 2003


 - posted 12-15-2012 10:07 AM      Profile for Mark Hajducki   Email Mark Hajducki   Send New Private Message       Edit/Delete Post 
It may be a result of the recent freezing weather we have been having.

I had a show cancelled due to a faulty LNB. Moisture gets into these during the year and then freezes, breaking the device.

When the LNB is in use it is heated, domestic (Sky) systems are powered up all the time (to receive the EPG etc) so it is not normally a problem with them.

The commercial (BBC world, Swedish God channel etc.) tend to be broadcast at a higher signal strength than the cinema broadcasts so checking with them does not always reveal a fault.

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Geoff Power
Film Handler

Posts: 37
From: Pershore, Worcs, UK
Registered: Apr 2012


 - posted 12-15-2012 11:40 AM      Profile for Geoff Power     Send New Private Message       Edit/Delete Post 
Thanks Mark - another excellent suggestion. We've had a week of very severe frosts up to Thursday, and our installation guy is also thinking it may be a faulty LNB

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