In reply to MaxWilliam:
> High gain digital aerials…
There is no such thing as a digital aerial. They're all UHF aerials. The "digital" appellation was added by marketing types before analogue TV was switched off, although it meant nothing in real terms: an aerial is an aerial, it doesn't care what's been modulated on to the radio waves it picks up.
Usually, "digital" actually meant "wideband" ie capable of receiving all the UHF TV frequencies, something which you often did need pre-DSO to receive the lower-power digital muxes which were squeezed into gaps between the analogue channels at the main transmitter sites. Hence also why high-gain was useful, because the digital muxes were broadcast at low power.
Post-DSO a high-gain wideband aerial shouldn't really be needed unless you are in a very dodgy reception area. Even then, a grouped aerial is probably preferable since it will be better at rejecting frequencies you don't want, which can be important if you are in a poor reception area and may well become more so as more of the old analogue UHF channels are sold off for things like 4G.
> You do need a decent co-ax cable however, which is foiled screened
A decent downlead is important but - assuming the terminations are sound - old brown coax is quite likely to be perfectly OK if it's only ever been run internally (exposure to the elements is much more likely to knacker downleads than being comfortably indoors). I'm getting six (soon to be eight) muxes of digital TV including HD very happily off old 1960s brown coax which was installed when the house was built. It would a complete pain to replace since it runs down inside the wall cavity, which has since been filled with insulation!
Again, digital TV signals are just RF, so if the current downlead doesn't exhibit any problems carrying RF signals from loft to sitting room then I'd say there's no pressing reason to replace it with WF100/CT100 unless it would be a trivially straightforward job. Digital TV is actually more resistant to many kinds of interference than analogue, due to the error-correction built in to the encoding. I would be strongly inclined to make any patch leads eg from wall socket to TV/STB, from CT100 in preference to the cheap white plastic rubbish you can buy, which has about as much screening as my big toe.
If appliances on the premises such as thermostats for central heating or fridges are creating impulse interference then there's a good argument for fixing those, ie cure it at the source, rather than simply trying to make your TV signal more interference-proof. (A new CH thermostat probably costs less than replacing the old coax with CT100.)
If money is no object then by all means pay for a brand-new aerial installation, but in a lot of cases it's simply not required and a more pragmatic approach is just to upgrade the stuff that's straightforward to get at first, and fix actual problems if and when they arise.
