I bet i know what it is. It's the same thing i have been seeing for the past 3-4 years. The first time i saw it was around the late 80's or early 90's. It would cause a poping in the audio of DMX music service. Back then, that was about the only digital satellight feed available.
Then the next time i saw it was in late 1998, when a tech in a system in NE MO asked me to take a look at a problem he was having with some of his satellight feeds. It would cause his satellight receivers to scramble for a second then come right back up. It would hapen about every 10 or 20 seconds.
In early 99 i started noticing it it a system where i was working. The problem seemed to get worse as i payed closer attention to it. Then started to notice that it would cause the digital video channels to tile about every 10 seconds. Sometimes it would be more intense than others, but would always be in 10 second intervals. It would start in the mornings around 7:30-8:00 am, and continue throughout the work day, with about an hour break around lunch time, then pick back up in the afternoon about 1:00 pm and usually stop around 5:00 pm. Just about like a normal work schedule, 8-5 with an hour lunch.
I'm still not sure what the signal is, but i have been seeing it regularly since 99. It may do it for a week at a time or maybe 2, then stop for a month or so. But one thing is for sure, it travels through the air like a off-air signal. When co-channel conditions are at there worse stage, it will be much more intense.
This problem drove me nuts for a couple of years, and i tried my best to find out where it was coming from, but had no luck. The best fix i could find for it, was a 3.7-4.2 ghz waveguild bandpass filter. It mounts on the dish between the feed horn and your LNB and filters out anything above and below the frequencies used by the c-band satellights. These run about $3-500.00 a piece and you need 2 for every feed horn. In my case this was only a 90% fix. You could still see a little bit of it, but it seemed to help out quite a bit. I would say it was worth the money.
The signal you are looking for can be found at 1780 mhz on a analizer, looking through a 950-1450 LNB. When you see this, it will only pop on for a split second, so you will needto use the peak hold to catch it. The carrier isn't in the c-band freq range, but just above it. The interferance you are seeing is the harmonics, or splatter off of the 1780 mhz. The amplitude of this signal will be twice the power of your satellight signals.
That's about all i can tell you about it. Get yourself some filters and that will clean a lot of it up.
Re: Interference ???
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