I have an application that requires RF to be propagated for several
hundred metres behind a vehicle at 433 MHz.

I am looking for ideas for an antenna that could be built into the metal
enclosure that houses the electronics. (ie. A single square or round
enclosure).

Ideally the field would fan out behind the vehicle and not have any side
lobes. (Only want RF behind the vehicle).
I am not worried about vertical propagation, Mainly just parallel to the
ground about 1.5m.

I am not sure if maybe I could get a corner reflector, patch antenna,
PCB loop, parabola or slot antenna into a fairly small surface area
(around 200mm x 200mm).


The transmit power is 25mW.

Any ideas much appreciated.

Thanks

Regards

David