Thread: UHF Load Design
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Old April 12th 04, 05:19 AM
Jerry Martes
 
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"George" wrote in message
nk.net...
Yep, there is. I'm designing a very small hand-held antenna for direction
finding. The smaller the better. On paper so far I have shortened
"half-wave" dipole elements to 0.32 lambda and am giving up 1 dB of gain

in
the process, assuming the coils I mentioned in each side of the dipoles.

Now the question becomes, is it practical and buildable?

BTW, congrats on your numbers! I, too, have seen a big improvement in my
own cholesterol numbers as a result of diet and exercise, not to mention
overall fitness ... )))

George K6GW



"Irv Finkleman" wrote in message
...
George wrote:

What's the best reference source I can use for designing loads in UHF
antenna elements? (To make physically shortened elements electrically
full-size.) For example, 200 ohms reactive at 500 MHz with Q 75-100?

Thanks.

George K6GW


Just curious, George! Because antennas at that frequency are relatively
small to begin with, I've never considered loading anything like that.

I'm curious
as to why you would want to -- there must be a good reason, isn't there?

Irv VE6BP
--
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58"/43"(!)/44" (already lower too!)
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Irv Finkleman,
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Irv


George

I'm not sure of the lengths of your "dipole" elements . I'm going to
assume you have a 1/2 wave dipole antenna shortened to about 1/3 wavelength
overall. That would have two identical elements about 1/6th wavelength
each. If this understanding is correct, I could suggest a method of
including 200 ohms in series with each 1/2 of the dipole.

A 1/6th wavelength long piece of 120 ohm coax would look like a 200 ohm
inductor if it was shorted at its other end.
Perhaps I could describe a method of building an antenna by using two
pieces of 100 ohm coax. It would look much the same as a conventional
centerfed dipole but its total length would be shorter than the usual 1/2
wavelength. If you dont already have a picture of what I'd try to describe,
maybe I can write more. But, I want to consider the outside of the coaxial
stub to be the radiating surface.

Jerry