Hi Christian

On Mon, 16 Oct 2006 14:53:13 +0100, "Christian McArdle"
wrote:

Result is that we have a little (oval - perhaps 80cm ?) sat dish up on
the gable end - with a clear view of the sky....

You need a bigger dish, probably round, not the little ovals you can use in
SE England.

So I was told before we moved out here - but I thought the 'experts'
would know what they were doing ?


The aerial is a 4 dipole + reflector arrangement, that they've
fitted in the loft (where it has to look through two concrete
walls and is about 1ft from an enormous steel 'I-beam' which
forms the ridge of the house. To compensate for this,
they've added a high-gain amplifier....

Ditch the amplifier. Waste of time. Amplifiers compensate for long downleads
or splitting. They are no good for rescuing below par aerial installations.

Thanks - you're confirming my own suspicions

You have ghosting. There could be two causes of this. Firstly, your noisy
loft installation. Secondly, being close to a high power transmitter. I
can't say which problem you have.

Not sure how much power the transmitter is putting out - about 2kw
according to Wolfbane

The first will be fixed by installing outside. The second would be fixed by
using a log periodic aerial instead of a Yagi. Log periodics have lowish
gain (but do you care?) but, more importantly, are very good at eliminating
reflections without all the spurious peaks you get on a Yagi response chart.
You basically point at the transmitter and get a good signal.

The existing aerial's a sort of '4 dipoles and a single mesh
reflector' arrangement - not a Yagi

If you have a really stubborn fixed reflection, such as off a large building
or mountain, you might need something more exotic, such as a Yagi phased
array, although these can be very problematic to set up (particularly
wideband) and are very sensitive to slippage from being blown around.

Wouldn't think we'll need that....

Thanks - I'll call them back in
Adrian