> Well I was going to post a photo of the actual antenna since of
> course the diagram is too simple however this was not possible (
> long story ). I have built a number of these and have better things
> to do if they did not work.
I don't doubt that they work; electrically small antennas work; I just
don't believe that you can get high efficiency and wide bandwidth both
simultaneously. My point was that I was surprised to see that the CFA
was so simple -- "just" an end-loaded dipole. I'd envisioned
something more subtle somehow, but I didn't know what/how.
>There is a phase relationship ... only a resistor
>exhibits in-phase voltage and current....
No argument on these points (as far as lumped elements go).
> ...the variable cap does indeed alter the phase of the current in
> the wire ( H ) and the voltage across the plates ( E ).
I contend that the variable cap. can not alter the phase of the
current in the wire ( H ) RELATIVE to that of the voltage across the
plates ( E ). The voltage across the plates is determined by the
charges on the plates, which is just the time-integral of the current.
The current in the wire is essentially uniform along the wire.
> . . . There is a reason for the antenna dimensions ( for operation
> at 28 Mhz ) that may not be clear. ( calculating the reactance of
> the two plates at 28.5 Mhz might give you some clues).
I haven't bothered to calculate this reactance, but other comments on
the NEC-LIST have suggested that it may be -j377 ohms. (Right?) I
see no reason why this value has any special significance. (Yes, I
know, sqrt(muzero/epsilonzero)=377 ohms, but so what?)
73 -Chuck W1HIS
Received on Sun Feb 28 1999 - 04:33:22 EST
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