On Thu, 17 Mar 2005 01:10:07 GMT, Carter Grabarczyk
wrote:

I am using a Johnson KW Matchbox antenna tuner with a 130 foot long, 30
foot high dipole fed with about 40 feet of ladder (window) line. It
works well on all bands including the WARC bands *except* for 30 meters.
(it doesn't make any difference if the band switch is on 20 or 40--it
will not tune 30 in either case).

The question is, does anyone have any tips/suggestions/modifications to
make this also operate on 30 meters?

By the way, modifying the antenna is not an option--lucky to have it up
at all with city and subdivision restrictions. Maybe could add extra
ladder line in the basement shack, but would have to loop it around the
basement ceiling???

73,
Carter
K8VT

I also have a 130 foot low dipole fed with ladderline. My feedline is
47 feet, going to an mfj tuner. I can tune 30 meters easily. You might
try adjusting the length of your feedline. You're using a different
tuner, so what you do may not match what I do, but playing with the
length of your feedline may help. Then again, it may not :-( Guess
that's why they call it amateur radio...

bob
k5qwg

Bob Miller wrote:
I also have a 130 foot low dipole fed with ladderline. My feedline is
47 feet, going to an mfj tuner. I can tune 30 meters easily. You might
try adjusting the length of your feedline. You're using a different
tuner, so what you do may not match what I do, but playing with the
length of your feedline may help. Then again, it may not :-( Guess
that's why they call it amateur radio...

"Playing" with the length of feedline may not help but
making it about 54 feet long will solve the problem. A
little cut-and-tryin' will eliminate the need for a
tuner altogether. Of course, 54 feet of window-line may
put the impedance out of bounds on some other band.
--
73, Cecil http://www.qsl.net/w5dxp


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On Thu, 17 Mar 2005 01:10:07 GMT, Carter Grabarczyk
wrote:

I am using a Johnson KW Matchbox antenna tuner with a 130 foot long, 30
foot high dipole fed with about 40 feet of ladder (window) line. It
works well on all bands including the WARC bands *except* for 30 meters.
(it doesn't make any difference if the band switch is on 20 or 40--it
will not tune 30 in either case).

The question is, does anyone have any tips/suggestions/modifications to
make this also operate on 30 meters?

By the way, modifying the antenna is not an option--lucky to have it up
at all with city and subdivision restrictions. Maybe could add extra
ladder line in the basement shack, but would have to loop it around the
basement ceiling???


Dear Carter,

As the owner of a cherry Viking Kilowatt Matchbox Tuner, I would want
to avoid any modifications of the tuner itself. So, what I do is build
up a modular approach for connecting feedlines to the tuner's balanced
terminals.

I use the General Radio design banana plug adapters as the basic
building block. They are available from Radio Shack and have the
advantages of having the exact spacing to match the 450 ohm ladder
line and being both a jack and a plug at the same time as screwing
down the ladder line.

My approach is t ohave a short piece of 450 ohm ladder line from the
Tuner Terminals to a GR banana connector. The antenna feed line has a
similar GR banana connector at its end. When lighting is in the
vicinity I disconncect the connectors and throw the feedline to the
floor or to an earthing.

Whenever I need a matching network for a given antenna due to extreme
mismatches, I build that network between two GR banana connectors and
just plug it in series with the line and tuner. The network is usually
as simple as two inductors wound on PVC or it could be just a mica
transmitting cap or a vacuum cap or any combination or balanced L or
Pi circuit components.

It helps to have a means of measuring the misbehaving antenna's
impedance at the end of the feedline at the frequency in question and
then design and build the necessary matching network based on the
Smith Chart solution.

Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html