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J-Pole 2M Antenna - possible tunning?

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Reginald M. Honyben

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Jul 8, 1996, 3:00:00 AM7/8/96
to

Last night I built my own 2M J-Pole antenna. To my pleasant surprise
it worked pretty well.
However I did receive this SWR readings:
on 144.000 MHz I received 1 to 1.15 ratio,
on 146.000 MHz I received 1 to 1.5 ratio,
and on 148.000 MHz I received 1 to 2 ratio

I like to transmit in the higher end of the band, around 147.000 to
148.000 MHz. Can anyone tell me how to tune the antenna so it is a
little more balanced, throughout the band? Or are these readings OK,
and I am over worrying? Thanks in advance!!!

My E-mail address is {ic...@asuvm.inre.asu.edu}
KC7MXV
73's

Rich Griffiths

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Jul 9, 1996, 3:00:00 AM7/9/96
to Reginald M. Honyben

At first look, those readings just mean that the 1/2-wave portion of the
antenna is too long, and trimming it about 2% would make it right. You
might also have to adjust the taps on the stub.

But then again, it may depend on how you built the antenna -- twin lead??
copper tubing?? other???

Also, please be advised that you should avoid testing exactly at the band
edges (144.000 or 148.000 MHz). If you do, some part of your signal is
almost certainly out of band.


Rich Griffiths W2RG

Mel Dixon

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Jul 11, 1996, 3:00:00 AM7/11/96
to

I agree with Rich, Your data indicates the antenna is a little long. If
you can, trim it down a bit, find the lowest SWR point and re-set the
tap. WB5BTG...

Kevin Pounders

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Jul 16, 1996, 3:00:00 AM7/16/96
to Reginald M. Honyben

Reginald M. Honyben wrote:
>
> Last night I built my own 2M J-Pole antenna. To my pleasant surprise
> it worked pretty well.
> However I did receive this SWR readings:
> on 144.000 MHz I received 1 to 1.15 ratio,
> on 146.000 MHz I received 1 to 1.5 ratio,
> and on 148.000 MHz I received 1 to 2 ratio
>
> I like to transmit in the higher end of the band, around 147.000 to
> 148.000 MHz. Can anyone tell me how to tune the antenna so it is a
> little more balanced, throughout the band? Or are these readings OK,
> and I am over worrying? Thanks in advance!!!
>
> My E-mail address is {ic...@asuvm.inre.asu.edu}
> KC7MXV
> 73's

There are two ways you can tune a J-pole. First, you can adjust the
position of where you attach the feedline to the two vertical elements
(this will get you in the ballpark, sounds like you are already there
from the SWR readings you quoted).

Second, (I am going to make the assumption that your J-pole is made out
of copper tubing) drill a hole in the endcap of the short element.
Solder a 6-32 brass nut to the inside of the endcap, then thread a 6-32
brass screw into it from the outside. This will allow you to fine tune
the antenna (basically, this adjusts the length of the short element).

I hope this helps, good luck.

73, de KC8AFW
--

Kevin Pounders, KC8AFW
poun...@qtm.net

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