Posted by
N2EY on
Jun 17, 2005; 11:32am
URL: http://elecraft.85.s1.nabble.com/may-have-it-wrong-tp379460p379463.html
In a message dated 6/17/05 2:12:37 AM Eastern Daylight Time,
[hidden email] writes:
> Wayne N6KR wrote:
>
> "...what you
> described won't work very well, because both wires need to be about 33
> feet long at this frequency. By cutting one 33-foot piece of wire in
> half, you've made a 20-meter antenna :)"
>
> --------------------
>
> A modeling program like EZNEC predicts that a 33-foot center fed wire will
> show a gain of about 6.9 dbi on 7 MHz and about 7.1 dBi on 14 MHz. That's
> essentially no difference at all.
>
> Of course, that assumes no difference in matching network losses, which I'd
> not expect a KX1 user to see using such an antenna without a feed line. (Of
> course, if a coaxial feeder is used, then some means to holding down the SWR
> on the feedline is very important to avoid losses there.)
>
>
There's more to it, though:
On 40 meters, the feedpoint impedance will look like a resistance of a few
ohms and a reactance of several hundred ohms or more. Will the matching network
be able to handle that, and do it without undue loss?
73 de Jim, N2EY
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