I live in an area surrounded by hills with marginal UHF reception. We have a DIY antenna installation on a high mast using a triplex like the one in this illustration. For several years this antenna has worked well. More recently we have started having reception issues, mainly with the TVNZ mux. The antenna is difficult to work on but we brought it down once, discovered some rust damage, cleaned and checked it, and put it back up. This did not improve our reception, however.
The TVNZ channels are significantly weaker than other muxes. Sometimes we get fairly bad pixelation on them, other times they are perfect, even for several days. I can find no pattern to the differences. They don't seem to be related to weather or wind conditions, or any other obvious variables. Sometimes it just works well, other times not. The only thing I have found that might be a factor is tropospheric ducting, but I have no idea if that is actually affecting this.
I don't know what the signal and quality indicators on our receiver actually measure, but on TV3 both are always steady on 100%. On TVNZ the signal is usually around 86% with the quality jumping between about 35% and 60%. As far as I can tell, these differences do not seem to affect our pixelation much. Sometimes we get a good picture for long periods, sometimes not, but in both cases signal and quality measures remain about the same.
I want to fix this issue if I can and I would like to know if anyone has any ideas or suggestions about this. Would another antenna or a masthead amplifier likely make a meaningful difference? I have a masthead amplifier and as an experiment I connected it at the receiver end of the cable. I did it this way because of the difficulty in accessing the antenna. It did improve the signal and quality measures, but it did not prevent the pixelation. I don't know how much difference it might make if correctly installed at the antenna end, but because of the difficulty of doing this, I am not keen unless I could be fairly sure it would really help.