Re: NEC-LIST: CFA in short

Fractenna_at_aol.com wrote:

> In a message dated 2/22/99 5:27:46 AM Eastern Standard Time,
> bergervo_at_natlab.research.philips.com writes:
>
> <<
> They are: a size reduction (of about 100, compared with a 1/2 wave
> antenna) and at the same time a relatively large frequency range
> (about 1/20 to 1/50 of the operating frequency) and finally about the
> same gain as a dipole.
>
> This is extraordinary, because resonant antenna structures as we know
> them, could not achieve this. The first two claims would only be
> possible with a very low gain, which is in contrast with the third
> claim.
>
> To be specific: a shortened dipole (1/100 times the half-wave length)
> when tuned with an ideal inductor, would have a Q-factor of about one
> million. This would give it a 10000 times smaller bandwidth than the
> CFA claim. If this Q is reduced by Ohmic losses to about 100 (more
> in line with the claimed frequency range) then the gain would also be
> reduced to -40dB, much lower than the CFA claim.
>
> This should explain that the CFA claims are extraordinary. I leave it
> to others to speculate whether they are true.
>
> Greetings,
> Jos>>
>
> Nice summary Jos. I didn't realise they were claiming such for
> something SO electrically small.
>
> At least with (some) fractal antennae the field strength advantage
> when JUST electrically small (>1/12 wave) is ascribable to
> phasing. Don't know what miracle explains the (allegedly high) CFA
> field strength
>
> Does anyone know if the Henf ("Super C") antenna also makes such
> claims as the CFA?
>
> 73
> Chip N1IR

Hmmm, Thinking of the CFA as a dipole is IMHO not correct. Convention
seems to be that an antenna must be resonant before it will radiate (
efficiently ) .... note I said efficiently. I operate a 6 foot loop
antenna on 3.5 MHz. This antenna is well below the 'normal' size of
antennas for this band. Is this loop a dipole ? Bandwidth conditions
aside the antenna radiates because of the field conditions that exist
at resonance .... not because it is resonant. ( after all I could
show you plenty of resonant systems that do not radiate ). Resonance
is a means to an end. As far as radiation of EM goes you only have to
look to the sky above ... there are plenty of EM sources in the galaxy
that radiate across the full EM spectrum ... as far as I know there is
no 'antenna' involved at all ... so how does this radiation / power
conversion occur .

73 de VK3PGM
Received on Thu Feb 25 1999 - 06:39:04 EST