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

Carter,
Have you tried the other band selections?
'Doc

"'Doc" wrote in message
om...
Carter,
Have you tried the other band selections?

'Doc

For what it's worth department;

I use my LP version of the Johnson Matchbox in conjunction with a 40 meter
Delta loop feed with ladder-line. I tune it on 30 with the tap in the 20
meter position.

I also tune this same loop on the AF MARS frequency, way up the band from
the top of 75 ham band by 500 khz. It tunes it down to 3 to 1, using the
80 meter tap.

Just for info....your results may vary depending on millions of factors.

Dan/W4NTI

There are several options you can take..
Install a new set of taps on the coil for 30 meters (probably the best way
to go)
Add additional caps across the matching cap
Add a variable cap on the input link
Install taps on the input link
Add a variable cap across the output where the twin lead is attached
Except for the input link, lift all other cap ties to ground
And you can add another tap on the matching capacitor..on the other side of
the random wire tap and use these two together for the twin lead.


"Carter Grabarczyk" wrote in message
m...
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

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
Hi Carter, That's a very high impedance you are trying to match on
30m. Looks like the only options you have are modifying the Matchbox
or changing the Feedline lenght. Another poster gave some good ideas
on modifying your tuner. If you don't want to modify the tuner, then
feed the 130' dipole with 11.3' of 450 ohm line and then go 50 ohm coax
to the transmitter. Don't need a tuner. Or if you could lenghten to
ladder line to 56' that would give a good 50 ohm match, no tuner
needed.
This is a guess but I think you would need to lenghten or shorten the
ladder line 8-10' to get within range of the Matchbox.
Gary N4AST

wrote:
If you don't want to modify the tuner, then
feed the 130' dipole with 11.3' of 450 ohm line and then go 50 ohm coax
to the transmitter. Don't need a tuner. Or if you could lenghten to
ladder line to 56' that would give a good 50 ohm match, no tuner
needed.

There's a DOS BASIC program on my web page that allows one
to enter frequency, dipole length, and type of ladder-line
to obtain the length of feedline that will resonate the
entire antenna system. Your 56' is pretty close to what my
BASIC program says (54' for 10.125 MHz, 130' dipole, 450 ohm
VF = 0.9). As you say, this length gives a virtually perfect
SWR of 1:1 on 30m - no matchbox required.

The DOS BASIC program can be downloaded from:

http://www.qsl.net/w5dxp/imax.exe
--
73, Cecil, W5DXP


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Cecil Moore wrote:
wrote:
If you don't want to modify the tuner, then
feed the 130' dipole with 11.3' of 450 ohm line and then go 50 ohm
coax
to the transmitter. Don't need a tuner. Or if you could lenghten
to
ladder line to 56' that would give a good 50 ohm match, no tuner
needed.

There's a DOS BASIC program on my web page that allows one
to enter frequency, dipole length, and type of ladder-line
to obtain the length of feedline that will resonate the
entire antenna system. Your 56' is pretty close to what my
BASIC program says (54' for 10.125 MHz, 130' dipole, 450 ohm
VF = 0.9). As you say, this length gives a virtually perfect
SWR of 1:1 on 30m - no matchbox required.

The DOS BASIC program can be downloaded from:

http://www.qsl.net/w5dxp/imax.exe
--
73, Cecil, W5DXP


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Hi Cecil, thanks for the info, I will take a look. BTW I used one of
Reg Edwards programs to get 56'. I'd say 2' is close enough for
engineering approximations. Have you bumped your program with his to
see how they compare?
Gary N4AST

wrote:
Hi Cecil, thanks for the info, I will take a look. BTW I used one of
Reg Edwards programs to get 56'. I'd say 2' is close enough for
engineering approximations. Have you bumped your program with his to
see how they compare?

Reg once compared them and they were close enough for
government work. I assume a VF of 0.9 for 450 ohm window-
line. Reg may assume something different or allow the user
to enter the VF. In any case, it won't be exactly 54' or
56'. Some adjustment will always be necessary.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:
wrote:
Hi Cecil, thanks for the info, I will take a look. BTW I used
one of
Reg Edwards programs to get 56'. I'd say 2' is close enough for
engineering approximations. Have you bumped your program with his
to
see how they compare?

Reg once compared them and they were close enough for
government work. I assume a VF of 0.9 for 450 ohm window-
line. Reg may assume something different or allow the user
to enter the VF. In any case, it won't be exactly 54' or
56'. Some adjustment will always be necessary.
--
73, Cecil http://www.qsl.net/w5dxp

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Good enough!
Gary N4AST

If you put a 500pF cap in a box, with a couple of SO239 connectors so that
it's in series with the coax to the tuner, you'll probably be able to tune
30M.

Adjusting feedline length is another approach.
Hth.

73, Dave, N3HE
Cincinnati OH

"Carter Grabarczyk" wrote in message
m...
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.