TV Picture / Sound break up. Mast Head Amp Part_2

[Diyisfun]

Well I cant continue on this thread
//www.diynot.com/diy/threads/tv-picture-sound-break-up-mast-head-amp.446096/#post-3509786
Mods: don't be to quick to shut threads.
So my problem continues.
No BBC, I did a retune & channels not found, next day channels found, then picture break up on ITV.
I am thinking its an external issue due to the weather/water poor connection etc.
So now all channels are ok so I cant do any testing until I lose the signal. Cables are already to start switching feeds etc, when I lose signal.

The LG inbuilt signal strength metre its showing about 45% on most channels, is this figure correct seems low to me.

 

[Lucid]

All the muxes being low doesn't sound right unless you're receiving the Freeview Lite service from a repeater station. You can tell this either by looking it up or by a quick glance at the aerial. The boom of the aerial has short 'fins'. If they're parallel to the ground then you're almost certainly receiving from a main transmitter (or your aerial is installed wrong ). The fins vertical means you're probably aligned to a relay transmitter. Have a look at your neighbours aerials; they should all be oriented the same way.

The way digital TV transmissions work is they take a channel frequency that used to be used for a single channel in the analogue days (say BBC 1) and send an encoded signal that bundles up a whole raft of channels. This is "multiplexing", so we call the signal channel containing a multiplexed signal a 'Mux'. Depending where you live and whether you receive the full range of available channels from a main transmitter or a reduced service (lite) because your location is covered by a smaller repeater mast. If your local mast is a full service transmitter then you'll be getting the main public service broadcast (psb) muxes at high power. These are the ones that provide BBC, ITV, Ch4 and Ch5 as well as the HD services. There are lower power muxes for commercial channels that aren't part of the public service remit.

My aerial points at Winter Hill. It's one of the more powerful transmitters in the country. The aerial on the roof is a log periodic, and it is unamplified. The BBC muxes give me 90-100% on quality and about 80-90% on strength. If I look at a channel on one of the low power muxes, say ch80 (ShowBiz TV) then the strength is lower - approx 30-40% but the quality is still high at 80+%. Strength in itself doesn't tell you much. The real indicator to look at is Quality.

 

[Diyisfun]

The aerial is the same as both neighbours, parallel to the ground. On the main TV I receive full HD.

 

[ericmark]

Had same with Mothers TV I was pulling out my hair. Even got an aerial installer to test it who said aerial was A1.

However when looking in the menu of TV saw I could set TV to give power to the aerial mast head box instead of using an external power supply. On doing this TV worked A1 no more problems. Clearly intermittent fault on the power supply. Since aerial fitter used his special box when testing which also has the voltage out for amp it worked A1 for him. And since power supply was cold when he plugged it back in power supply worked for his test but failed again latter.