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Old January 6th 05, 07:45 PM
Cecil Moore
 
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Bob Miller wrote:

On 6 Jan 2005 06:54:32 -0800, wrote:
Also, do you have to ground or use a balun with a jpole? I have seen
some plans that say you dont on their design.


A lot of hams just coil up a few turns of coax beneath the
J-Pole as a choke to keep the feedline from radiating (much).

http://www.qsl.net/ares_d24/jpole450.jpg has plans for a 450-ohm
ladderline j-pole which is designed for 2 meters, but also works on
440 mhz with low swr, probably at reduced efficiency, but mine still
works there, okay. (I don't use a balun.)


A 2m J-Pole used on 70 cm has a takeoff angle of about 47 degrees.
The gain at 15 degrees is more than 3 dB down. It works, but a lot
of the RF is lost at the higher radiation angles.
--
73, Cecil http://www.qsl.net/w5dxp


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