(57) In microwave communication systems it is common practice to use a beam waveguide
to transmit energy between a waveguide (2) connected to transmitting and receiving
equipment located at ground level and a main antenna reflector (not shown in Figure
3) mounted above ground level. Hitherto the waveguide (2) has terminated in a very
large, accurately machined, horn which is necessary to produce a beam having a small
angle of divergence suitable for entry into the beam waveguide (6).
The present invention proposes that this large (and very expensive) horn be replaced
by a relatively small horn (18) which produces a beam having a relatively wide angle
of divergence. By using a concave reflector (22) and a sub-reflector (21) in Cassegrain
configuration this widely diverging beam is converted into a more nearly parallel
(or a totally parallel) beam which enters the beam waveguide (6) as illustrated.
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