Re: X Beam aerials

In article <46fb5ceb$0$313$4d4eb98e@xxxxxxxxxxxxxxxxxxx>,
Paul D.Smith <paul_d_smith@xxxxxxxxxxxxx> wrote:
"Al" <alnews67@xxxxxxxxxxx> wrote in message


Not sure I agree with the ghosting explanation but Bill Wright is the man
who'll know. I can tell you that Bill has a nice article on his website
about using TWO aerials carefully aligned together in order to improve
ghosting and I believe I've seen him say more than once that two simpler
aerials used in this way are normally better than a single "more
directional" aerial.

Leaping in ahead of Bill: "it all depends".

'X-beam' aerials as you call them, often called 'High Gain' aerials, tend
to have a narrower forward lobe than a conventional Yagi. However, to
compensate, they tend to have odd rear lobes which vary from channel to
channel. If there are strong reflections from the rear, high gain aerials
can show ghosting sometimes only on one channel. If, on the other hand the
reflection is from the front and to the side of the main signal, the narrow
front lobe can often reject the 'ghost'.

A carefully set up pair of aerials can be arranged to null out reception in
any given direction, but again this will vary from channel to channel.
It's a very time consuming business.

Another way of rejecting signals from the rear is to use a log periodic or
a grid (or bow-tie) aerial. Of course, these have the drawback of low
gain, but it's always possible to amplify a low, but clean, signal.

the choice of which type of aerial to use depends on the circumstances,
which is why an experienced aerial rigger needs to get involved when there
is 'ghosting' in the area.




--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

.

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