Dear Martin and LF Group,
The CFA antenna has been doing the rounds for a while - the
problem is, like most "miracle" antennas, it does not seem to live
up to it's claims in real life.
Nobody, including the inventors, seem to be able to get
reproducible results from the CFA; clearly, it does radiate some
signal, but as amateurs are well aware, just about any bit of metal
can be coaxed into radiating a reasonable signal some of the time.
At least one Australian broadcast station found that their CFA
antenna worked better tuned against ground in a conventional
manner, rather than using the "crossed field" principle.
The anecdote about the Egyptian broadcast station does not really
stand scrutiny - a lambda/4 MF broadcast antenna should have an
efficiency of 80% or more, so to get 6dB improvement, the CFA
would have to radiate 4 times more power, ie. 320% efficiency, or
more than 3 times as much power as is being fed into it from the
transmitter. The other possibility is that the comparison antenna
was extremely inefficient, for reasons unknown.
A 6.5m tall CFA scaled from 1.16MHz to 136kHz would be 55m tall -
basically funnel shaped, a solid metal cylinder around10 metres in
diameter, with a big cone made of mesh about the same diameter
as the height for top loading, driven against a solid metal ground
plane. So it really should be quite efficient, whether it embodies
any new operating principles or not, and could not be called "small"
by amateur standards.
Unfortunately, the CFA seems to have got surrounded by a lot of
"pseudoscientific" hype, so it is difficult to tell serious information
about it from the junk.
Cheers, Jim Moritz
73 de M0BMU
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