On 10/13/2014 11:00 AM, Wayne wrote:


"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.

Yes, but an isotropic source is an imaginary tool used for comparisons.
It obviously cannot exist in the real world, but it's spherical
radiation pattern can be used as a standard for comparisons.

Similar to an inductor or capacitor with no resistance - only reactance.
They don't exist in the real world, but are used to simplify
calculations. Once you get an answer, you can tweak the results for the
resistance.

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