Message-ID: <3950DE60.A9647BEF@club-internet.fr>
Date: Wed, 21 Jun 2000 17:25:48 +0200
From: "M & S" <sovergne@club-internet.fr>
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: CFA Antenna: miraculous?
References: <3.0.1.16.20000621103659.0af713fc@mail.cc.kuleuven.ac.be> <394F7643.7AC83ACF@club-internet.fr> <3.0.1.16.20000621135302.12f7ace4@mail.cc.kuleuven.ac.be>
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Hi Rick, Hi all,


I'll be constructing one of these antennas starting from next weekend.
All the literature about it seem's so interesting that I will absolutely
try one.

I'll start with 160 meters and give you the results.

Then, I'll try one for 136 kHz

In the mean time, my full-size dipole has been repaired with success.
Reception is very good. Just wait for that big signal from the
south-west of France...

73, Mark, F6JSZ
JN04PX
http://perso.club-internet.fr/sovergne

Rik Strobbe a *crit :
> 
> >I found only two papers reporting field strenght measurement, one
> >from supporters and one from a dectractor of CFAs:
> >
> >1) WA6HZT and N6YIP in Antennex (June 2000) report a loss of 24 db
> >respect to the filed strenght predicted by models for a
> >quarter wave monopole with 120 radials, for their 1.6-m high CFA on
> >160 meters. However they declare that this result is provisional,
> >while they are still trying to build better tuning networks.
> >
> >2) VE2CV in the same journal reports a radiation efficiency of about
> >1% for his 1.2-m high CFA on 80 meters
> 
> This would mean that a 0.015 lambda CFA has a gain of about -20dB (2) and a
> 0.01 lambda CFA has a gain of about -24dB (1).
> Extrapolating this figures would lead to -30/-35dB for a 10m high CFA on
> 136kHz (about 0.005 lambda) and -35/-40dB for 6m high CFA.
> These are values that one can achieve with a decent T or inverted-L antenna
> of the same height.
> 
> I do not doubt that the CFA principle works, but when the size of the
> antenna becomes very small (compared to wavelength) you will get high
> losses. For a short vertical these are mainly in the 'surrounding'
> (grounds, nearby objects) while for the CFA (as for the magnetic loop)
> these are probably within the antenna. This could make the CFA a valid
> alternative for those sufferering from very high groundloss.
> 
> 73, Rik  ON7YD