Hi Allan,
Would imagine this would also work on the DB212 Antenna. Could you give me a
little more info on the cables as i am a little sloe
Wesley AB8KD
----- Original Message -----
From: wa9zzu
To: Repeater-Builder@yahoogroups.com
Sent: Friday, August 21, 2009 3:11 PM
Subject: [Repeater-Builder] Re: DB-224 Matching
-Well guys,
With all due respect to Jim and his tried and true dipole modifications in
which he changes the load impedance presented to the cable harness which is in
turn reflected to the 1st junction connected to the antenna pigtail, and all
the others who do some sort of extensive dipole modification to get a resulting
VSWR to their liking, I find that the simpliest and most rewarding, easiest,
least labor intensive, not to mention least possible to create mechanical
problems, is the addition of just two short lengths of 50 ohm coax at the
antenna feed point coax, one in series and one in shunt, to a tee connector.
This matching section has been done to several DB 224 antennas by my self with
great success.
No strain, no pain, and only a minimum of cost and time, with low VSWR over
the 144-148 band.
And I challenge any one to tell the difference in the gain of the DB224 using
the original dipoles with my impedance matching section to the modified dipoles
with the loss in the mismatch created in the antenna harness with the modified
dipoles.
All it takes is some effort with a Smith Chart and some simple coax cable
construction after measuring the feed point impedance / VSWR at the band edge
and the center frequencies from 144 to 148 MHz. All done at gound level. Simple
matching stub design can be found and is well described in the ARRL Antenna
Book, 13th edition on Pp. 122-126.
I have done this same type of coaxial impedance matching on several of the DB
420 antennas as well with good results.
73 Allan Crites WA9ZZU
-- In Repeater-Builder@yahoogroups.com, "tahrens301" <tahr...@...> wrote:
>
> Hi Jim, thanks for the words on corrosion, and Laryn... aah, the
> voice of experience! No holes will be drilled!!
>
> Thanks to all. I believe that will be the easiest way to make
> it work.
>
> Tim W5FN
>
>
>
>
> --- In Repeater-Builder@yahoogroups.com, "larynl2" <larynl@> wrote:
> >
> > Perhaps
> > > drilling a hole through the original element for
> > > connection might be better.
> >
> >
> > Uh, I wouldn't drill holes in elements. I did drill small holes in each
of four elements years ago and within a year all four elements had cracked
right where I drilled.
> >
> > Laryn K8TVZ
> >
>
