[Paparazzi-devel] Patch antenna 2,4 GHz

[Helmut Wabnig]

On Fri, 15 Feb 2008 12:00:02 -0500, you wrote:

The 2,4 GHz diagonal edge cut patch antenna is only the second best
choice, because it is not very well circularly polarized
(only a few percent)
and difficult to manufacture without measuring equipment.
You must keep mechanical tolerances below 0,1 mm.
Industrial made antennas are available, but make sure they fit the
frequency range, because patches are very narrowband.

For the ground station you better make a helix antenna which is very
easy to manufacture and is much more uncritical in the 
mechanical tolerances.

http://helix.remco.tk/


The model  airplane will be flying around you in all directions
and the antenna must be able to receive from 360 degrees
azimut. Therefore the helix must not have more than about 6 turns
and must be oriented vertically upwards or may be oriented
slightly towards the airplane flying area.
The more turns on a helix, the narrower the receiving angle.
The circularly polarized helix will pick up signals in either
direction, and more than compensate the theoretical 3 dB
polarization loss by it's high gain.


Mount the TX antenna on the bottom of the airplane
either horizontally or vertically downwards.


It would make sense to integrate a "conformal" patch antenna
in the airplane wing bottom. Try to find home TV receiver remote
controls on the flea market.
http://www.conrad.at/goto.php?artikel=350498 
Dismantle the antenna case.
They contain ready made 2,4 GHz patches. Those patches
can be mounted "conformal" into the bottom side of the wings.
Make sure to have the same handedness for both antennas.
(left or right wound helix)


w.