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Re: LF: Re: CFA (once more)

To: [email protected]
Subject: Re: LF: Re: CFA (once more)
From: "Rik Strobbe" <[email protected]>
Date: Tue, 11 Sep 2001 11:15:35 +0100
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Hello Alberto,

Thanks for your comments. I have also a lot of sceptisism in regard with
CFA (and similar) antennas but as they say 'eating is the proof of the
pudding' (or something like that), so I have more faith in test results
than in theoretical discours.
As far as I know radioamateurs have tested CFA / EH-antennas on shortwave.
I you scale the relative sizes and mounting heights to 136kHz it often
comes to an almost 50m heigh constructions mounted at several 100m above
ground, I have no doubt that this would make a wonderfull LF antenna.
Constructing a 10m high CFA or EH-antenna mounted at groundlevel would
already be a big challenge to most of us, if you size that down to 20m you
get a 10cm high antenna that you have to put on the ground. I wonder if any
CFA of that size will work. But on the other hand we don't need to go for
80 or 90% efficiency, I would be more than happy to achieve 1% efficiency.
Bernd (DF8ZR) has built a 20 EH-antenna and will test it at different
heights above ground. If this antenna really works the way the inventors
explain then then signalstrength should be relative independent versus the
height. If the signal strength raises by 6dB when doubling the mounting
height then it might  just function as an ordinary vertical with a very
funny tophat.

73, Rik  ON7YD


On this subject, this last weekend I went to a hamfest in Piacenza, Italy,
where some commercial prototypes of the EH Antenna were presented.
They had a couple of Yaesu FT-1000MP, one connected to a full size
dipole for the 40m band, and the other to an EH antenna for the same band.
I asked if I could play a little with them, they said 'yes, of course'.
Then I tuned a faint CW signal with both receivers. The full size dipole
outperformed the EH but only by a slight edge, which apparently was
remarkable, given the difference in size. But then I went outdoor, to look
at both antennas. The EH was installed just half meter above the center of
the dipole.... hmmm... I suspect a strong coupling between the two...
probably the lines of force of the electromagnetic field were made denser
by the dipole in the proximity of the EH antenna...

Then I asked for a further test on the 20m band, where no dipoles were
installed, using this time an indoor EH antenna, mounted on a 2-meter tall
support. They agreed, and even connected a microphone to the transceiver.
The 20m band was rather quiet (it was about noon on Saturday), with only
a few signals. I called a Cyprus station who called CQ Contest, but no
answer.
Then I found another station, an SV1, also calling CQ. This one answered
me,
giving me an S5 report, but then he failed to answer a question I posed
him,
showing that my readability was less than perfect...

All in all, I am quite skeptical about this antenna, theoretical
considerations aside.
A friend OM regularly makes QSO with a 1.5m whip, base-loaded, from his car
on the 7, 14 and 21MHz bands, so this new EH antenna seems to perform
nothing
more, nothing less than a short loaded dipole, not worth the money they
ask for
it, nor the troubles for building it.

Just my opinions.

73  Alberto  I2PHD





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