Tuning problems- help wanted

Magilla Gorilla

I was getting 95% signal strength on my Samsung Tv from Kippure. Lately, this has fallen to 40%, with significant break-up during rain etc. Connecting directly to the aerial (avoiding Sky box, diplexer etc.), the very best I can get now is 85%. My VHF signal has degraded too.

I've checked aerials, all cabling, connections etc. but found nothing unusual. Has anyone else noticed any problems?

My TV was in for repairs recently. There was a speaker probelm. Is it possible that the tuner could have been affected by the repairs so that it's "partly" working? I can't say for sure that the signal was perfect just before the tv went in, but certainly these was no break-up.

Any ideas?

lucernarian

Easiest way to check this is to use an alternative TV set to check analogue signal quality and find any flatscreen TV or DVB-T box to scan in the mux. It won't be able to show pictures, but you'll be able to tell what the signal strength and quality is like on a saorview mux even without MPEG4 support.

It does sound like an aerial/water ingress issue though. If your signal strength is that good, have you tried putting the aerial in the attic? Saorview isn't affected by the ghosting that can happen with an aerial inside the attic and saorview can work at weaker signal strengths than the analogue signal can, giving saorview a better chance of reception within an attic.

watty

Quality rather than level is important.

lucernarian

Yes watty but while signal quality is more important, signal strength can be indicative too. For example, a scenario where someone has intermittent loss of reception while normally having signal quality 100% and signal strength 90% would indicate one thing. Another user with problems while signal quality was normally 100% and signal strength was at 42% would mean a different cause was more likely.

If a signal strength bar by itself is at 100%, it doesn't tell anything whatsoever about how close the signal is to an increased BER.

I wish DVB-T receivers would have something like a signal to noise ratio meter (like ADSL modems) rather than the signal quality bar, as that only really tells you if there's a BER of greater than 1x10^-7 or something like that.

Magilla Gorilla

Thanks folks.

The tv only displays signal strength. Right now it's showing strength at 40% with bit eror level 7 (out of 10). Previously, it was 95%, with 0 error.

My Sky box is connected on RF only, not Scart, and is displaying perfectly. This seems to indicate an aerial problem, as the tuner is obviously able to process the Sky box input on UHF without any problems.

I have VHF and UHF aerials on the roof, using a Fringe conbiner so only one downlead to inside the house. Could the combiner be kaput? Is there any way of checking without buying a new one?

Peter Rhea

Magilla Gorilla wrote: »

. . . Could the combiner be kaput? Is there any way of checking without buying a new one?

Just bypass it & see if it makes a difference (Connect the UHF downlead and combined downlead together).
Is the diplexer you referred to in the 1st post for terrestrial & sat? Also what channel does the Sky box output RF on?

Magilla Gorilla

Yes, looks like I'll have to bypass it, which means fun on the roof!

Yes, the diplexer combines terrestrial and sat, so only one lead down to tv point, where I've a splitter.

Sky box outputs on channel 48.

watty

And negatively on Ch47
Domestic RF modulators eat next lower channel and interfere with others.

Peter Rhea

watty wrote: »

And negatively on Ch47

Are you sure you're still receiving from Kippure/Three Rock?
If you're in Kildare would it be possible to pick up Cairn Hill (ch47)?

Magilla Gorilla

Definitely Kippure, clear line if sight to it and that's where my aerials are pointed.

Weak signal round here from Cairn Hill- it seems I'll have to further examine the combiner. But it looker dry as toast when I opened it yesterday. Are there bits inside that can fail? It's probably 5 years old (or more) at this stage.

Watty, ch 48 for Sky box has worked all along, this is a recent development. But I'll try a different setting to see if it makes a difference.

Magilla Gorilla

Just an update which might help someone.

Went through all the options today- bypassing diplexer, wallplate, Sky box etc. Eventually found that the cable feeding the signal from the aerial was the culprit. No obvious signs of damage or anything; I can only guess the severe frost around Christmas caused some damage.

Relaced the cable and signal is now up to 75% with no bit errors, so no picture breakup.

Curious, but I'm happy the tv is not the problem!