It is a feature of television signals that they can be effected by the weather. Aside from the obvious damaged that can be caused by wind or torrential rain, the onset of summer can cause a more intriguing problem called "inversion".
Basically, when the sun heats up the land, the hot air can get trapped below cold air at high level. This creates an "inversion layer" which acts like a polished mirror to TV signals. This causes two problems: you can receive both the original and a reflected signal from your own transmitter (on analogue TV this appears as "ghosting") or interference from TV transmitters that are normally too far distant.
The ITV/C4 multiplex of channels (ITV-1, ITV-2, ITV-3, ITV-4, CITV, C4, More4, E4, Quizcall) use a transmission "mode" called 64QAM, and it is sadly much more prone to these problems.
So, whilst a loft-mounted aerial will provide reception at some time, it will fail at others. The only real solution is to mount the aerial (or a new Class I aerial) outside on a pole, but some people report that changing the cable from the aerial to the set-top box to the high-grade satellite cable can also help.
The SCART connection, by the way, only carries a single TV picture, not the Freeview transmission multiplexes, so if this is disconnected it will result in degradation to every channel at once.
I have 2 types of digitalbox receivers. But have stop working and cannot find any channels about 1 month ago. One is downstairs one is up. I checked the leads on each box and the cable up to the roofaerial is intact.
doug: Any query involving problems with reception "has" to be accompanied by a location, this preferably being in the form of a post code or one from somewhere nearby, e.g: a Post Office, as this info enables access to details of the transmitter (including coverage of) serving the area.
However, as you are connected into your own aerial system the problem has to be caused by a fault somewhere in same, as its highly unlikely that two boxes would fail at the same time, and although you haven't mentioned it as such, but if your two aerial outlet points are fed via any type of powered splitter?, try connecting the downlead from the aerial directly into the TV as the splitter could have failed.
That said is on the assumption that you have "not" tried retuning your boxes after having found no reception, because if you have? whilst the transmitter covering your area was either down, or alternatively was operating on reduced power for maintenance purposes, the action of retuning under said conditions will have cleared everything stored in the boxes memory, further retuning being required in order to load the channels back into the memory.
jb38: hi ty for the info. I would guess then that the splitter has failed. I have tried to re tune the channels on several dates split apart in case of local problems. It seem to Co- inside with a cable theft attempt in the local area. My post code being da175hg
doug : Now its been confirmed that a powered splitter is indeed being used, then your problem is likely to be down to failure of the devices internal power supply, bypassing the device instantly revealing whether it is or not.
Although as you will probably find out, if not already known!, bypassing the device requires a "female" back to back coax coupler, (approx 75p) as you will end up with two male connector plugs, this also applicable if screwed "F" connector plugs are being used, although in this case, a female "F" back to back coupler would be required.
As far as attempted cable theft in your area is concerned, the only thing that would affect your own reception (apart from a failed booster) is by someone removing your aerials downlead.
By the way, Crystal Palace would appear to be the transmitter covering your area, albeit that the line of sight from same is blocked at two separate locations starting from just under 4 miles out, this possibly being the reason why a booster is required.