The digital freeview signal is quite sensitive to electromagnetic interference, and chief conduits for this interference are the mains supply, aerial cable, and when the weather is foul enough, the very skies above. Assuming you haven't provoked the wrath of the Gods, the first two can be sorted out.
Firstly, a mains conditioner will do a great job of filtering out problems caused by poorly shielded central heating pumps etc. If you haven't come across these, they look like conventional multi plug strips with a copper torus on one end. Tacima make an excellent 6 plug strip with mains conditioner and radio frequency filter which I can personally say completely cured heating pump related Freeview picture break up (anecdotal evidence of one and all that).
The aerial connection can be similarly improved, though doing so is slightly more involved than plugging in a different power strip. As they are so inexpensive, I fitted a screened wall plate for the aerial connection for good measure. These are pretty much ubiquitous now the analogue signal's been switched off, in fact in a moment of idle curiosity, it was quite hard to find an old style open wall plate online.
Here's the patient in question. I basically followed the great instructions at aerialsandtv.com, but there aren't any surprises here if you'd rather go it alone.
|The finger of suspicion, pointing out an unscreened TV wallplate. And a rather poor paint job.|
With the two securing screw removed, the open construction of the wallplate can be revealed.
|No screening to speak of here!|
|With the old plate discarded, here's the coaxial aerial cable,|
ready to be stripped back for connection to the new one.
After taking a stanley blade to the outer sheath and plastic insulation around the copper core, it was time to open the new wallplate's packaging.
|Preparing the cable. Looks to be the lower quality kind.|
Here's the new wallplate - basically just a socket for the coax with a metal box surrounding it. Pop the copper core in the socket, tighter down the central screw, then close the hinged panel and screw that down too. That's that really! Set the plate back on the wall with the long screws provided, and everyone's happy.
|About the close up.|
I'll sign off by saying that those plastic cased sub £30 freeview recorders that use USB sticks as PVR memory are particularly prone to interference issues, so consider some clip on ferrite cores on the flyleads as well if using them!