Mendip Transmitter Reception Problems

Background Info

Just before Christmas I started to experience reception problems with our Freeview Digital TV receiving from the Mendip transmitter. The TV is only about two years old and has been receiving Digital Freeview from this transmitter since its installation, fault free. The date of the problem starting does not coincide with the ITV West Digital Switch over, and has started to occur some time after the full switch over.

Problem

After initially switching the TV on, the picture and sound will gradually worsen to a point where it is no longer possible to watch any programmes. A “first time install retune” usually resolves the problem for about an hour or until you switch off. Switching the TV back on again you will be offered about 20 mins of watching the reception breaks up.

Suspecting that the internal TV tuner was duff I plugged in a stand alone set top box to see if this would remedy the reception problems. Using the set top box (connected to the TV via SCART and independent of the internal TV tuner) the reception problem remains…after an initial period of use the channel reception deteriorates to an unwatchable mess of noise and pixels.

Suspecting that the Aerial and/or Coax was at fault, I have replaced the aerial and coax with a new installation and yet the problem STILL remains on both TV and Set Top Box.

Using the TV diagnostic tools (admittedly not accurate but good enough to see what’s happening at the aerial/ tuner interfaces) the Signal Strengths are being indicated at somewhere between 80% and 100% when directed at the Mendip transmitter. Signal quality is fluctuating between 90% gradually deteriorating to 25%, with the reception problems starting around 50%.

I have browsed various TV related internet pages and subsequently found a local relay transmitter (6miles away) and re directed the aerial to that, and whilst the signal strengths improved across the channel ranges, I can only successfully tune 30 of the 103 channels available. Also looking at the neighbouring houses the majority point at Mendip.

I am a bit stuck as to what else to do…I don’t know if an amp will do anything as from what I can see for some reason there is a weakening of the signal over time starting strong and gradually weakens off…

I have manually retuned the TV and box to the various Freeview Channels instead of the automated approach and makes no difference…the signal still deteriorates

The aerial is polarised in the correct direction, however I have tried it in other positions upside down, on its side, even reversed, again makes no difference other than the obvious problems doing this causes.

Which leads me to think of the following

Interference - however I don’t see any pattern v’s time of day?
We are sat in between two (three including the relay) transmitters (Mendip and South Wales) and therefore one is blocking the other…although we don’t get any Welsh TV.

Any other thoughts on what else I can do/ try?

The Mendip transmitter is not working very well at the moment although nobody will admit that. It is running on some temporary channels and some muxes are on low power. It probably wont be resolved until at least September but more likely not until 2013. Freeview will always have problems due to overlapping signals from other transmitters. With Mendip we get overlap from Wenvoe and Stockland Hill and probably Ridge Hill when they go digital. I always recommend the Satellite services, either Freesat from Sky or freesat. Never needs retuning and much better pictures!