On 11/2/2013 10:10 PM, Dan Hearn wrote:
Tom: The use of a coil of coax as a choke is a poor solution to the problem
of feed line radiation. It is affected by the feed line length and distance
to ground. Not only that, it is not well suited to use over the 3 bands of
your antenna. Modern technology using ferrite cores allows you to generate
thousands of ohms of impedance over a wide frequency range. Design of these
chokes is covered on K9YC's web site. They are simple and inexpensive to
They don't need the fancy cases although they look nice.
http://www.rogerhalstead.com/ham_files/AntennaFeed2.htm
This is feeding a 75 meter fan dipole. One about half this
size will work across the entire 20 through 10 range with about 5000 ohms.
Download K9YC's tutorial and look at what's needed in 2.4" diameter #31
mix cores.
These are extremely effective.
The fan dipole shown is thought of as a balanced load, but with one end
above 90 feet and the other at roughly 10 feet it is far from being
balanced.
It actually takes two of these chokes to keep RF out of the shack at the
legal
limit. One you see in the photo, the other is at the point where the feed
line reaches the tower. With only the one choke at the feed point, every
LED
in the shack would light up at roughly one KW out.
The really nice thing about them is they are very broad banded where the
old
solenoid coil often worked, it was effective on only one, or two
adjacent bands.
These tribanders would normally work with non at all which is why they
appear to work with
the narrow band, solenoid coil.
IIRC Jim has a graph of one or several solenoid coils for comparison.
Good Luck es 73,
Roger (K8RI)
build or you can buy them from Balun Designs or Array Solutions for way
under a hundred bucks complete in weather tite cases. . The cores are made
by Fair Rite and can be bought from Mouser or other parts houses.
73, Dan, N5AR
On Sat, Nov 2, 2013 at 5:43 PM, W1JCW <w1jcw@hotmail.com> wrote:
No.
Go with a 5 turn 6" diameter RF coke at the feed point per Mosley
instructions.
I've had several Mosley antennas over the years and have never had an
issue with RF.
73-
W1JCW
John
--------------------------------------------------
From: "Tom Nicholson" <Gunsrus1942@Comcast.net>
Sent: Saturday, November 02, 2013 3:45 PM
To: <TowerTalk@contesting.com>
Subject: [TowerTalk] Dumb question on Mosley TA33
Is there anything to be gained from feeding the TA33 with a 1:1
balun??????
Tom, W1ALZ
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