Tacolneston uses ch59 for Public Service Broadcast 2 (PSB2) and that's running at 100,000W which is very powerful.
https://ukfree.tv/transmitters/tv/Tacolneston
Check your signal strength via the TV tuning menu. In general, put your telly on to ITV, then go in to the tuning menu and select Manual Tuning. You might see something along the lines of:
Search Type: Digital Aerial
Channel: 59
Frequency: 778.00MHz (or 777.8 if the tuner isn't rounding up)
Signal Quality: (something here, a number or a bar of some wording)
Signal Strength: (something here, a number or a bar of some wording)
__________________________________________________________
Quality (Q) is the most important. You're looking for 60-100% - the higher the better
Strength (S) is less important. This part can always be boosted with an amplifier, but too much signal strength causes as many problems as too little. 40-60% could be plenty of strength to get a good solid lock. If you're maxed out at 100% then it might be that you have too much signal.
There are five other mux channels on your transmitter that are also running at 100,000W. These are:
PSB1 (BBCA) C55
PSB3 (BBCB) C50
COM4 (SDN) C42
COM5 (ArqA) C45
COM6 (ArqB) C39
and so the natural question is why aren't these affected too. The answer is probably to do with your aerial. The sensitivity of an aerial isn't flat and equal throughout the frequency range. Most have a profile with a hump. At some frequencies they're good, and at other frequencies they're poor.
For the last 15+ years the common aerial type being sold and installed has been the
wideband high-gain. It sounds like the perfect solution;
wideband makes it seem like it gets everything, and
high-gain would suggest that it produces lots of signal strength; so who wouldn't want that combination? Unfortunately it's marketing ********.
Here's the profile for this type of aerial (black curve) compared to the flattest reception type - the Log Periodic (orange curve)
Graph explained: Across the bottom axis are the channel numbers 21-60. The vertical axis shows the gain (amplification) of the signal due to the aerial. The black line is the gain curve for a decent wideband high-gain aerial. You'll notice the curve rises up as the channel numbers gets higher. Once you're up in to the high 50's then the aerial is producing its strongest signal. This aerial gets close to 12dBd. That number is on top of whatever the field strength is for your local area. This means that for C39 we get field strength + 9dB roughly, and for C59 we get something along the lines of field strength + 11.7dB
Depending where you are, you home might already be getting high field strength. Alternatively, your original installer might have put an amp on the aerial feed and that's boosting the strength. Either way, the gain at c59 could possibly be right on the upper limit of what the TV needs, then something changed locally that has tipped it over the edge. Maybe someone had some trees taken down in the direct line of sight from your aerial to the transmitter? Stranger things happen.
The point is that a decent installer should have a professional signal meter and be able to look at the relative signal strengths of all the muxes then balance any amplification or signal strength to ensure that there's neither too much or too little. There shouldn't be too much "best guess" or "suck it and see" in any service call. If they haven't got the right gear then they'll waste time groping in the dark.
This is my meter showing the relative levels for 5 of the Winterhill muxes. I'm using an un-amplified Log Period and I'm about 30 miles as the crow flies from the transmitter.
Check out your signal levels to see if things are getting overcooked. Come back with the results.
