John S wrote in :

On 11/6/2014 11:33 AM, gareth wrote:
"John S" wrote in message
...
So, it appears that doubling the length of a short antenna captures about
3.6 times the signal.

And, therefore, by the reciprocity characteristic, the short antenna is
an inefficient radiator?

No, not at all. If the kind of reciprocity to which you refer were true,
then the receiving antenna would capture ALL the power radiated. That
obviously cannot be, so I think your idea of reciprocity may be a bit
flawed.


Jim said something the other day that made it clearest for me. He said (of
reciprocity, and not verbatim) that if some field arriving at an antenna
created some electrical signal at its feed point, then recreating that signal
would recreate that field at the antenna itself. My interpretation of that is
that while a receiving antenna, made bigger, captures more energy from a
diverging field from another source, this cannot be equated with transmission
where the whole energy source is transmitted from the antenna regardless of
size if impedance matching is good.