nospam:

That cb antenna (with the 3 dipoles arranged so as to go omni/directional)
was called a "scanner", made by antenna specialists I believe (reed
switches in a relay box control the elements.)

I cut one down, along with the phasing harness to the center of the 10
meter band, works great! And you are correct, the three 120 degree spaced
vertical dipoles are fed in phase for omni-pattern.

John

On Sat, 20 Aug 2005 18:22:29 +0000, nospam wrote:

On Fri, 19 Aug 2005 20:21:38 +0000 (UTC), "Reg Edwards"
wrote:

There is a 3-phase transmitter feeding a 3-phase antenna via a 3-wire
transmission line.

The antenna consists of three 1/4-wave horizontal radiators spaced at
120 degee intervals.

Is the radiation pattern in the horizontal plane perfectly
omni-directional?
----
Reg.

No. Effectively you are feeding two legs with a -120 degree phase
and that will make it directional.

For Omnidirectional operation ALL legs will have to be fed in phase.
If the three sources are laggin in phase then the feed system will
have to correct the phase till all are in phase.

Many years ago, there was a CB (USA 27mhz 11m) that used three
vertical dipoles with phasing to get directionality or omnidirectional
gain.


Allison