Weird satellite problem

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Slab Bulkhead
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Weird satellite problem

Post by Slab Bulkhead » Thu Aug 30, 2018 7:50 am

I've run into an odd problem with a satellite dish. Station has XDS receivers for Premiere and Learfield. The Learfield receiver is working fine, Premiere stopped working. Ops guy requested a new box from Premiere, they shipped it out, still no signal. He's tried all sorts of swap outs to rule out cables, splitter, etc., even bypassing the splitter and connecting the dish directly to the Premiere RX. Freq and symbol rate are set correctly and the receiver has been activated, but still no signal.

I'm inclined to think the LNB is at fault since everything else has been ruled out, but another guy they use says the LNB should be an "all or nothing" and if the Learfield box is working the Premiere should be too. Could we be getting some source of frequency specific interference that's affecting Premiere but not Learfield? The dish pointing should be fine, because Learfield shows plenty of signal, a 13 or so Eb/No.

Nathaniel Steele
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Re: Weird satellite problem

Post by Nathaniel Steele » Thu Aug 30, 2018 9:49 am

Have you put a spec an on it? I'd check the cross-pol. And compare your received signal to published spectrum plot.

I've also found this site to be helpful for comparison. You can view the spectrum of (Almost any) satellite

https://satsignature.com/plot/america/amc-15-ses-11

jammerdave
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Re: Weird satellite problem

Post by jammerdave » Thu Aug 30, 2018 9:50 am

Premier has had ongoing problems for nearly a month or more. No word from them at all about it. Just crickets. Some of us have very low signal from that carrier, and folks like you have nothing. Go figure.

awsherrill
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Re: Weird satellite problem

Post by awsherrill » Thu Aug 30, 2018 10:11 am

Just looked at our Premiere receiver and the EB/NO is full scale. If they are having problems, it is not evident here (NC).

I'm wondering if different transponders can have coverage issues that affect their footprint, to the extent that some parts of CONUS have boatloads of signal and others are barely above muting threshold. Several years ago when one of the broadcast birds had a partial transponder failure, different parts of the country had either OK signal or nothing.

Agree that you need to look at the LNB output on a spectrum analyzer, to see if there is interference on that specific frequency.

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kkiddkkidd
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Re: Weird satellite problem

Post by kkiddkkidd » Thu Aug 30, 2018 10:47 am

jammerdave wrote:
Thu Aug 30, 2018 9:50 am
Premier has had ongoing problems for nearly a month or more. No word from them at all about it. Just crickets. Some of us have very low signal from that carrier, and folks like you have nothing. Go figure.
I have a client with much the same problems for a month or so and am wondering if it is an adjacent bird interference problem.

Premier RX stopped working. All 3 or 4 other RX's working fine with slightly lower but near normal numbers. This dish is a substandard but large TVRO mesh on a polar mount w/ de-motorized TVRO feed but has always had very decent and reliable signals (Even on WW1).

Premier has sent 2x receivers and neither would acquire reliably and neither would show more than a 2-3 EB while the other rx's (ESPN, WW1, etc) was 10+. I slightly warped the dish around and determined that it needed to be moved slightly eastward. Did so and the Premier RX now has 10ish EBNO while the others have only increased into the 12's. And when I say slightly, I mean almost imperceptibly... Since we were dodging tstorms, I didn't hook my specan up at the dish but we did check the polarity using the Premier EB and it was spot on the best numbers at it's original position.

The owner said that the EB jumped suddenly from 3 to 10(ish) and back down suddenly as I slowly rocked the dish back and forth thru the sweet spot. I don't recall it being that sharp in the original AMC18 migration. The other RX's didn't seem to be as critical.

Hence I am wondering if an interfering carrier has recently been fired off on an adjacent bird...

I was going to try the WW1 freq offset trick until discovering that the dish needed a tweek.

Good luck,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
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Nathaniel Steele
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Re: Weird satellite problem

Post by Nathaniel Steele » Thu Aug 30, 2018 4:37 pm

I just got a new RX from premiere, but I was having lockups with the box not responding and screwing up our time delayed programs. Live programming never glitched, EbNo's the same as they have been since I got here, about 11-12. I didn't install the dish here, as I was still out in CO (where i Did a half dozen or so), but I always suspected that the brand new DH dish should have gotten a little better EbNo, but it's always worked so I havent checked it with the spec-an yet. A TV engineer for the local PBS stattion did the install and he had the proper equipment and knowledge.

Anyway, I haven't noticed any problems and the new box hasn't locked up, its been in maybe 3 weeks now.

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kkiddkkidd
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Re: Weird satellite problem

Post by kkiddkkidd » Fri Aug 31, 2018 4:01 pm

And the problem Premier RX has surfaced again.

This morning my client called to say that they couldn't set the NetCue assignments nor schedule.

We quickly determined that the RX was on a vastly wrong IP (10.90.1.xxx when the local net was 192.168.1.xxx) AND was set for DHCP. I talked them thru turning off DHCP, setting a static IP, gateway, etc and it seems to be working fine.

All manner of weirdness...
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

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NECRAT
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Re: Weird satellite problem

Post by NECRAT » Sat Sep 01, 2018 8:23 am

Have you looked at the satellite downlink on a Spectrum analyzer to see what it looks like?

It's not unusual for LNBs to start "spiking" across the band, and you could have an issue where one of those spikes are near your desired carrier. Could also be cross-pole. Your cross pole could be a touch off, and on the opposite pole, at the same frequency , could be a "new" carrier that is causing your issue.
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Dale H. Cook
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Re: Weird satellite problem

Post by Dale H. Cook » Sun Sep 02, 2018 4:51 am

NECRAT wrote:
Sat Sep 01, 2018 8:23 am
Have you looked at the satellite downlink on a Spectrum analyzer to see what it looks like?
+1 A spectrum analyzer is a must for setting up a dish for a digital C band receiver in the era of 2 degree spacing. It is the only way to properly minimize interference from cross polarization. Going just by the Eb/No and AG readings is not sufficient as they do not tell the whole story, and only a SA will show you artifacts such as LNB spikes and terrestrial interference.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
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Slab Bulkhead
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Re: Weird satellite problem

Post by Slab Bulkhead » Sun Sep 02, 2018 7:58 pm

NECRAT wrote:
Sat Sep 01, 2018 8:23 am
Have you looked at the satellite downlink on a Spectrum analyzer to see what it looks like?

It's not unusual for LNBs to start "spiking" across the band, and you could have an issue where one of those spikes are near your desired carrier. Could also be cross-pole. Your cross pole could be a touch off, and on the opposite pole, at the same frequency , could be a "new" carrier that is causing your issue.
As it turned out, it was cross-pol interference. A new carrier must have come up and knocked it out.

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