| My new antenna leverages off of
a lot of the work I did on the first ground plane antenna. It all
starts with a small square of pcb board cut out of the original XCam2's
patch antenna. The primary difference is that the hole in the middle
of the board only has to be big enough to thread the internal coax insulation.
To determine the size of the hole, read on...
|The most significant design change I made
to my antenna was to replace the coax cable that came with the XCam2.
After repeated experiments, my original cable was getting thrashed, so
I needed a replacement. I selected RG174/U, available from Hosfelt
Electronics for $.19 per foot. In this picture I've already prepped
the coax by stripping 5cm of the outer sheath, cutting the braided shield
down to about 6 mm, and tinning the shield. The exposed signal wire
will act as the main radiating element.
|A couple of things have occurred in this
picture. First, the pcb board has been threaded over the signal wire
and is resting on the top of the tinned coax shield, with the copper
side down. Second, the pcb board was firmly soldered to the coax
shield from the underside. Third, the four ground wires were soldered
to the pcb board in a pin wheel pattern. This is shown better in
the next picture.
|Here is a detail shot of the four ground
wires as they are soldered onto the base of the antenna. By soldering
then in a pin wheel pattern, I was able to get more of the wires in contact
with the pcb board, thereby giving me a stronger solder joint.
|This is the final antenna shape.
The four outer wires are bent down at a 45 degree angle from their former
position, and cut to exactly 3cm in length, measured from the bend.
The signal wire is also cut to 3cm, measured from where the signal wire
exits the coax shield. There is no additional support for the signal wire
since I wanted it to have a little bit of "give" in case of an accident
(I've bent more signal wires while handling the plane than I have while
This antenna gives an approximate 15 degree
up-slope to it's coverage area, so it will give good coverage when mounted
pointing down on the airplane.
|That completes the construction of the
revised ground plane antenna!