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I0OJJ > ANTENN 01.07.10 21:03l 34 Lines 1346 Bytes #-5797 (0) @ WW
BID : 12488I0OJJ
Read: GUEST
Subj: Re: language and antenna gain
Path: DB0FHN<DB0MRW<DK0WUE<IK6ZDE<I4UKI<I0OJJ
Sent: 100701/1848z @:I0OJJ.ILAZ.ITA.EU #:6152 $:12488i0ojj
-.-. --.- wrote:
> "Richard Fry" <rfry@adams.net> ha scritto nel messaggio
> news:f8abc033-9c19-437f-a0fe-8309cb370897@c10g2000yqi.googlegroups.com...
>
>> But that does not mean that it has all of the electrical
>> characteristics of a linear conductor that is inherently resonant,
>> without the need for inductive loading.
>
> Yes, replying to Richard but also to Roy and Dave.. maybe i can't explain
> very well, but the sense of my latest question is this:
>
> if a half wave end-fed *monopole* antenna have the following primary
> characteristics (if IIRC):
>
> - High Z at the feedpoint (voltage maximum and current node);
> - very small counterpoise lenght compared to the resonant wavelenght of the
> antenna (typical 0.1-0.2 lambda)
>
> can i mantain the same characteristics shortening the antenna in any way ??
>
> Thanks for read and explain to those who want clarify my doubts.
>
> -.-. --.-
You can add a top hat to a vertical that's shorter than a half
wavelength, and bring it to anti-resonance (high input resistance with
no reactance). The impedance won't be as high as if the antenna were a
half wavelength high, and it will have narrower bandwidth, so it won't
be a perfect imitation. Or you can use a combination of loading
inductance and top hat to get a somewhat poorer imitation.
Roy Lewallen, W7EL
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