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What would cause this interference


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Old 22-04-2016, 18:37
AlanO
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Ok - here goes.

We've got a roof aerial aimed at Sandy Heath.

There's a distribution system in the loft serving several rooms.

A couple of channels are having real problems.

Using the signal detection feature on my Humax DTR 1000 I can see:

Ch48 Strength 40% (stable) and quality 100%
Ch51 Strength 38% (stable) quality 10% -30% variable
Ch52 Strength 40% (stable) quality 100%

So what could be causing the problem on Ch51? Any ideas?
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Old 22-04-2016, 19:31
Evo102
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You're not using a HomePlug named Winston by any chance?
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Old 22-04-2016, 19:39
Helmut10
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Those signal strength meters are not very accurate, pretty meaningless % number. You must be close to the threshold where the quality quickly drops.

Some servicing of the loft distribution system and aerial would be in order. The extremes of temperature in a loft would take it's toll over time, and weather on the roof aerial/cables etc.
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Old 22-04-2016, 20:11
AlanO
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You're not using a HomePlug named Winston by any chance?
Oddly enough I am. That said I don't get why Ch51 is virtually unusable but Ch52 is OK.......
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Old 22-04-2016, 20:42
chrisjr
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The way digital telly works means that you can get near perfect reception down to quite low signal levels and then it just appears to drop off the edge of a cliff.

If the "cliff edge" for your Humax is something like 36-38% then Ch. 52 will be safely away from the cliff edge but Ch. 51 is clinging on by it's fingertips.

Well worth checking out the aerial to make sure it is still in good working order and getting the best possible signal in to the distribution system. And also check out the distribution system and cabling down to the TVs is also OK.
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Old 22-04-2016, 22:40
Chris Frost
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So what could be causing the problem on Ch51? Any ideas?
Kinked or bent co-ax cable: It can cause a narrow-band notch filter which attenuates a small part of the frequency spectrum and it causes exactly this sort of issue. Read more here from the Satcure web site

I wouldn't rule out other causes, but given your description and how closely it matches the sort of thing that happens with damaged or poorly routed cable then I'd be tempted to start with that first before looking for more exotic causes.
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