A better method might be to actually cut each half of the element at about the
mid-point (not at the bend - at the straight section), then slide some smaller
tubing inside. Slide the element ends in and out while testing and then use
some stainless screws to attach things back together at your new length. I
suppose you could also measure the length of the "extension" and cut that
length from a piece of tubing that is the same size as the original element.
This would effectively "hide" your repair and keep the element the same
diameter for the entire length.
Chuck
WB2EDV
----- Original Message -----
From: Jim Brown
To: Repeater-Builder@yahoogroups.com
Sent: Sunday, March 22, 2009 6:13 PM
Subject: Re: [Repeater-Builder] Re: Decibel dipole array sweeps
I have done the mod mentioned on several DB-224 antennas by taking some
six inch lengths of an old TV antenna and flattening about three inches on one
end and wrapping the flattened end around the end of the dipole and putting a
machine screw through the flats to hold the extension to the dipole. I then
cut the extension back to two inches.
This has resulted in a lower SWR in the ham band after moving the 155
mHz antennas down. I have made no changes to the harness to move the antenna.
Something like a change from 1.8:1 down to 1.2:1 is what I have measured at the
antenna.
73 - Jim W5ZIT
--- On Sun, 3/22/09, Tom, N6MVT <n6...@comcast.net> wrote:
From: Tom, N6MVT <n6...@comcast.net>
Subject: [Repeater-Builder] Re: Decibel dipole array sweeps
To: Repeater-Builder@yahoogroups.com
Date: Sunday, March 22, 2009, 4:09 PM
Also, I have seen some of the dipoles get modified with short
stainless machine screws+nuts drilled through the top & bottom of the dipole
elements, to help get the Return Loss even better at lower freqs.
Not sure what, if any, skewed pattern is introduced by doing the
machine screw mod or not. Quite often it's hard to tell any changes in the
field unless it is very drastic.
Tom
