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Old October 5th 07, 10:00 PM posted to rec.radio.amateur.antenna
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Default j-pole 5/8 wave

On Oct 5, 2:42 pm, Ed Cregger wrote:
wrote:
On Oct 5, 11:49 am, K7ITM wrote:
On Oct 5, 6:45 am, wrote:


Higher?? You posted 6.34dBi for the half wave, and 6.58dBi for the
quarter wave GP ... Am I misreading something, or was that a typo
about which has higher gain, or what?


Dang.. I guess I had it backwards in the 2nd post...
Normally, I would think the 1/2 whip would show slightly higher,
but dunno.. Quiver in the force I guess.
I have no real problems with either type. A 1/2 wave whip is fine
if it's decoupled.
But few J pole users seem to add decoupling sections.
Most of the ringos sold for VHF lack decoupling also..
One note.. If I build a 1/2 wave, I usually prefer to feed as a ringo,
vs as a J pole..
But I still mostly use the GP's as they are simple. I've got one up
in the attic hanging from the rafters as an emergency antenna
when T-storms are in the area and I'm chicken to use my outside
antennas.
MK


Yes, BUT, the 5/8th wave radiator will put more of the signal toward the
horizon, instead of launching it at a 40 degree plus angle away from the
horizon. So while one configuration can have higher dbi ratings, it
doesn't count unless the signal goes where it will be most effective.


Dunno.. You sure you ain't got it backwards? Unless the 5/8 is on a
large
ground plane, etc, it's usually the one with the higher avg launch
angles
vs the 1/2 wave.
The 5/8 with no radials should be pretty bad at that.. Even a set of
1/4 wave radials under a 5/8 will give a fairly poor pattern.
If I were to build a j pole, it would be a 1/2 wave.
If I run a 5/8, I'd have two elements as a collinear, or at least
have 5/8 or 3/4 wave radials. I'd never run just a single 5/8 wave
radiator
on it's own. It's not a "complete" antenna like a 1/2 wave j pole is.
Or to my way of qualifying anyway...
MK


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