How about something like a Butternut Vertical antenna, which has a length
of 75 ohm coax between the antenna base and the 52 ohm feedline? Do you
make the choke coil out of the 75 ohm coax at the antenna base, or from the
52 ohm coax out past the junction where the two coax cables are joined?
LJ
Original Message:
-----------------
From: K8RI on Tower talk k8ri-tower@charter.net
Date: Tue, 4 Oct 2005 17:05:25 -0400
To: w8ji@contesting.com, k8do@mailblocks.com, towertalk@contesting.com
Subject: Re: [TowerTalk] Elevated vertical
>
> Elevated radials SHOULD have the feedpoint decoupled through
> a common mode choke. if you ground the radial common point
> is causes increased loss as well as current on the feedline
> shield.
How would you go about this with an antenna like the AV-640 which has a
built in tuning network that is grouneded. Isolate the entire antenna from
the tower, feed it through a choke, and atach the radials to the bottom of
the antenna where it would normally atach to the mast driven into the
ground?
In this case isolating the antenna from the tower is not going to be easy.
It's only 32 feet, but difficult to get at with *stuff* on the 100' tower
being much easter to work on.
73
Roger (K8RI)
>
> Conventional systems offer greater bandwidth and just as
> good or better efficiency. You do need a bit more wire, but
> it is significantly less critical what you do with the wire.
>
> Reliable FS measurements have shown eight resonant radials
> at 1/4 wl above ground are about equal with sixty radials on
> the ground.
>
> My own FS measurements both here and in Conyers GA showed
> four elevated radials at six feet height on 80 meters are
> down about 5 dB or more from sixty radials laid on the
> ground. At WVNJ six radials at 20-30 feet high were down 2.5
> to 4 dB from 60 radials on the ground, depending on the
> measurement point.
>
> I hope everyone against me in a pile up uses four (or better
> yet two) elevated radials.
>
> 73 Tom
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
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