Someone wrote:
I run my main TV from a digibox attached to an indoor aerial. I have always
supposed we have a pretty strong signal because we get all the digital
channels quite easily.

I bought a singing and dancing computer which is supposed to run digital and
analogue TV from an aerial socket. I have this in a different room . I am
not technical I dont know how it works. It came with a stick thing aerial. I
plugged it in and picked up 23 channels. Then suddenly they disappeared - or
rather they were all blank, happened over night.


Something is obviously amiss if you are picking up only 23 channels.
That room is a bad location for your aerial, possible that the aerial in
the other room is better placed to get a decent signal.

Get a two output aerial amplifier like the link and some CT100
'satellite quality' cable, and aerial plugs.
http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=AP01179

Screwfix probably are a good source as well (haven't checked!)

The purpose of this amplifier would be to boost whatever signal you
receive from your indoor antenna, and split it to supply your two
set-top boxes - also overcoming the noisey interference that PCs radiate
and whatever detrimental effect that the length of the cable may make
(though probably not much). Keep the aerial cable tied away from the two
cables leaving the amplifier.

A 'better' solution would be a distributed setup using a roof or loft
aerial, but more expensive - and come digital switchover (with increased
signal available) probabaly unnecessary in your already strong location
as you have described.

--
Adrian C