Dave, you're absolutely right, the existing antenna is 1/2 wave
end-to-end, not 1/2 wave per section.

As for your other suggestions - based on other reading, it seems like
J-Poles are finicky to attach to coax. And I've looked at
phased/stacked dipoles, looks promising but I worry about the narrow
vertical beampattern.

For an elevated ground plane scenario - what's better? Radials, trimmed
to resonant length, bent down 45 degrees or so (I've read since that
this is required for 50 ohm impedance) -- or a simple ground plane, 90
degrees to the axis of the 1/4 wave whip, min. 1/2wave diameter? 900MHz
is a pretty small wavelength, I'd be fine with using a solid 6.5"
ground plane if it would get me better performance than radials.

"jmorash" wrote in message
oups.com...
Dave, you're absolutely right, the existing antenna is 1/2 wave
end-to-end, not 1/2 wave per section.

As for your other suggestions - based on other reading, it seems like
J-Poles are finicky to attach to coax. And I've looked at
phased/stacked dipoles, looks promising but I worry about the narrow
vertical beampattern.

For an elevated ground plane scenario - what's better? Radials, trimmed
to resonant length, bent down 45 degrees or so (I've read since that
this is required for 50 ohm impedance) -- or a simple ground plane, 90
degrees to the axis of the 1/4 wave whip, min. 1/2wave diameter? 900MHz
is a pretty small wavelength, I'd be fine with using a solid 6.5"
ground plane if it would get me better performance than radials.

a solid ground plane would be more efficient, but is of course bigger,
heavier, and more wind load if you are worried about it blowing around. the
3-4 radials bent down gives an easy way to fine tune the impedance... of
course if they aren't stiff enough they can get bent if slapped around in
waves.

That makes sense. Thanks for the tips.

On page 16-23 of the ARRL Antenna Book, 19th ed, Figure 35B shows a
very simple vertical J design. It's open-stub, direct fed from (in
fact, pretty much made out of) 50ohm coax, with a 3/4 wave length of
core conductor and a parallel 1/4 wave wire coming off the shield.
Looks almost too easy... any thoughts on how this would compare to the
1/4 wave whip with ground radials? It's got a larger aperture, but I
don't understand how the grounding is meant to work...

Dave wrote:

a solid ground plane would be more efficient, but is of course bigger,
heavier, and more wind load if you are worried about it blowing around. the
3-4 radials bent down gives an easy way to fine tune the impedance... of
course if they aren't stiff enough they can get bent if slapped around in
waves.

Why would a solid ground plane be more efficient? What's the loss
mechanism in radials?

Roy Lewallen, W7EL