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RE: AO-14, UHF antenae revisited



November 1999) at 12/05/2000 02:45:01 PM
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Hello Tony,
      if my memory serves me correctly, approx 15 years ago, something
similar was tried here in Geelong.

Rod, VK3XOK(I think) worked as a radio technician, doing lots of "two way"
installations,
and he managed to get himself a couple of whips made by the manufacturer of
the whips
they were using for fleet  installations.  These were  supposedly made
specifically for 70cm.
The only difference here is that his use was for mobile fast scan ATV @
426.25MHz.
I can remember watching his pictures and tracking him as he drove around
Geelong.
Again, mym memory seems to recall the SWR was OK, and the pictures for most
part were
quite readable, with picture/audio "flashes" caused when he drove under
trees and when
a truck/bus crossed by him in the Tx/Tx line of sight.
Apart from that I think the test was successful, although he only did it
the once to my knowledge.
cheers

Ian VK3YIC





Tony Langdon <tlangdon@atctraining.com.au>@AMSAT.Org on 12/05/2000 01:29:44
PM

Sent by:  owner-AMSAT-BB@AMSAT.Org


To:   "'Wayne Day'" <n5wd@earthlink.net>, Norm McMillan
       <njmcmillan@bigpond.com>, amsat-bb@AMSAT.Org
cc:

Subject:  RE: [amsat-bb] AO-14, UHF antenae revisited


 > At 08:50 AM 05/12/2000 +1000, Norm McMillan wrote:
 > >Thanks to those people who replied. Seems like no-one has
 > tried to use a
 > >UHF CB antenna on 70cm.
 > >
 >
 > It appears that Tony, VK3JED has done just that, and K5OE has
 > the info on his
 > web page:
 >         http://members.aol.com/homebrewpics/
 >
 > G'luck!
 >
 > 73 Wayne N5WD

Not quite.  I modified a 1/2 wave, which is a bit easier, as there is only
one element and the matching network is more like an autotransformer
(tuning
there is less critical), so it was a simple matter of adding the necessary
length to move the resonance down from 477 MHz to 435 MHz.

In Norm's case, the antenna in question is a collinear with a 1/2 wave over
a 1/4 wave, and the two being connected by a phasing coil.  So _both_
elements would have to be extended, as well as some adjustments to the
phasing coil.  The element adjustments would be relatively simple, the
phasing coil might be a bit more of a challenge (or one could put up with
the slight phase error between the elements, and any effect that has on the
radiation pattern...).
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