Thank you Dave,

for sharing with me results of your simulation. I got similar results. The
thing that works is slit pipe (Alford's slot, see
http://www.eta.chalmers.se/~pgp/alfo...lford_eng.html for example)

Pipe works over ground plane as well (not as well, beam gets lifted, stll
there is enough energy looking on the horizon). It is such a cumbersome
thing though - looks funny on car's roof. Not of ractical use.

And I still can not find anything else that does it.


Regards,

Andrey Gleener


"KC1DI" wrote in message
...
Andrey wrote:
Greetings to all the antenna experts here!

I want to create horizontally polarized antenna, low profile, located
above
large ground plane. And I need it to be omnidirectional (sort of) and
have
sufficient gain in horizontal plane.

My frequency of interest is 900 MHz. The ground plane is a roof of a
car.

I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount
it
above the ground plane.

Any ideas?

Thank you,

Andrey


Good Morning Andrey,

What you are proposing is not an easy task any horizontal antenna placed
close to a good ground plain is going to have most of it's signal at
90 degrees. ( Straight up) Until the antenna is at least 1/2 wave above
the ground plan. at that point it will start to show radiation to the
horizon. EZNEC shows max gain at 30 degrees to the horizon for a 1/2
wave horizontal dipole mounted 1/2 wave above perfect ground and the
pattern looks somewhat like a peanut shape. if you move the antenna up
to 1 fullwave length above the ground plain then the patern does not
change much but the elevation angle dose you then get a good lobe at 15
degrees and another at 45 degrees. hope this is of some help.
Dave kc1di