Mike Coombes wrote:
Looking at the ARRL Antenna book it seems that the angle of radiation
is pretty well fixed on the type of antenna.

Talking about "the" angle (as if there was only one) is misleading
ourselves.

Every antenna has a *range* of angles over which it radiates (or
receives) the best. The aim is to make that coincide with the *range* of
angles over which signals are likely to arrive.

This is made very clear in the 18th edition of the Antenna Handbook
onwards. It presents arrival angles as a statistical range of
probabilities, over a spread of possible propagation conditions.

If you have only one antenna, then obviously you try to make its very
best radiation angle coincide with the most *likely* angle of arrival.
But it's a game of chance. Occasionally the angle may be very different
from the most likely value, so you have to accept that you're going to
be some dB down... or dead in the water. And that is where having a
choice of different antennas really scores.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek