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Old October 13th 14, 04:00 PM posted to rec.radio.amateur.antenna
Wayne Wayne is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 409
Default Short antenna = reduced power



"Jeff" wrote in message ...

Gareth, please have a look around the web and find a copy of Kraus to
download; then read, in particular, chapters 3 and 5.


In particular note the following in relation to short dipoles:


"Assuming no losses it [the power radiated] is also equal to the power
delivered to the [short] dipole"


"The maximum effective aperture of the 1/2 wavelength antenna is about 10%
greater than that of the short dipole"


The gains of a short and 1/2 wave dipole is also quoted as 1.76 and 2.14dBi
respectively.


So can we now put this to bed, the short dipole radiates well it is the
practicabilities that make it a poor antenna.


Jeff


And along the same lines, antennas are often described in terms of isotropic
(point) antennas. With radiation being related to length, isotropic
antennas would not radiate.

Also with effective aperture, the 10% greater you mention is a result of
orientation of the aperture with respect to the maximum part of the
individual antenna pattern. Considering the entire pattern of both
antennas, reciprocity is maintained.