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Old March 3rd 04, 06:37 AM
Theplanters95
 
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Default Mounting J-Pole

I have a all copper J-pole antenna. What is the best method to mount it? Can
the bottom piece (below the connector) be connected to a tv mast with clamps?

Randy ka4nma
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Old March 3rd 04, 01:48 PM
Stephen Cowell
 
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"Theplanters95" wrote in message
...
I have a all copper J-pole antenna. What is the best method to mount it?

Can
the bottom piece (below the connector) be connected to a tv mast with

clamps?

Yes... you can ground the antenna, in fact,
it is recommended.
__
Steve
KI5YG
..


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Old March 3rd 04, 03:54 PM
Dan Richardson
 
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On Wed, 03 Mar 2004 13:48:12 GMT, " Stephen Cowell"
wrote:
[snip]

Yes... you can ground the antenna, in fact,
it is recommended.


There is one problem not often mentioned with connecting a j-pole to a
ground mounted conductive mast. It can increase the amount of higher
angle radiation. Mast lengths that are multiples of ½-wavelengths are
the worst for this problem and mast lengths that are odd multiples of
¼-wave produce the least.

If the mast is not grounded (floating) then the situation is reversed,
½-wave would least high angle radiation and and ¼-wave the most.

NEC modeling has shown that for good low-angle radiation patterns
insulating a j-pole from a conductive mast produces more power towards
the horizon.

73,
Danny, K6MHE




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Old March 3rd 04, 04:00 PM
Jack Painter
 
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Default

I have a all copper J-pole antenna. What is the best method to mount
it?
Can
the bottom piece (below the connector) be connected to a tv mast with

clamps?

Yes... you can ground the antenna, in fact,
it is recommended.
__
Steve
KI5YG
.


Copper J-pole mast-mounted alongside chimney works extremely well for me on
vhf-marine. Mine is grounded with insulator-supported #4 solid copper wire,
not for antenna performance, but because it more than just resembles an
air-terminal / lightning rod! Because I use heavy feedline, there are no
decouping-loops just under the J-Pole as recommended by most designs. So if
my feedline is radiating, it doesn't seem to hurt the maximun distance I
obtain with that antenna. It works very efficiently far beyond the
theoretical radio horizon.

Jack
Oceana Radio


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Old March 4th 04, 01:46 AM
Bob Miller
 
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On Wed, 03 Mar 2004 07:54:25 -0800, Dan Richardson
wrote:

On Wed, 03 Mar 2004 13:48:12 GMT, " Stephen Cowell"
wrote:
[snip]

Yes... you can ground the antenna, in fact,
it is recommended.


There is one problem not often mentioned with connecting a j-pole to a
ground mounted conductive mast. It can increase the amount of higher
angle radiation. Mast lengths that are multiples of ½-wavelengths are
the worst for this problem and mast lengths that are odd multiples of
¼-wave produce the least.


From what I've read, there is practically no RF on the lower crook of
a "J" antenna, so why would using that crook as a mount and/or ground
attachment make much of a difference?

Bob
k5qwg



If the mast is not grounded (floating) then the situation is reversed,
½-wave would least high angle radiation and and ¼-wave the most.

NEC modeling has shown that for good low-angle radiation patterns
insulating a j-pole from a conductive mast produces more power towards
the horizon.

73,
Danny, K6MHE


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Old March 4th 04, 02:58 AM
Dan Richardson
 
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On Wed, 03 Mar 2004 19:46:16 -0600, Bob Miller
wrote:

From what I've read, there is practically no RF on the lower crook of
a "J" antenna, so why would using that crook as a mount and/or ground
attachment make much of a difference?


There is little RF voltage but there is a very high level of RF
current.

The same situation you find in the center of a ½-wave dipole (low
voltage/ high current).

Danny, K6MHE

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