I had a buddy who did physically lengthen the two ends of each dipole by
cutting them and inserting aluminum tubing and welding the assembly back
together. His brother in law was good at aluminum welding. Again, he did not
change anything in the harness and the antennas work fine now in the ham band.
73 - Jim W5ZIT
--- On Sun, 3/22/09, Chuck Kelsey <wb2...@roadrunner.com> wrote:
From: Chuck Kelsey <wb2...@roadrunner.com>
Subject: Re: [Repeater-Builder] Re: Decibel dipole array sweeps
To: Repeater-Builder@yahoogroups.com
Date: Sunday, March 22, 2009, 5:30 PM
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
