| My new antenna departs from my last
design in one significant way: The small bit of copper pcb board that made
up the base of the antenna is completely gone. Instead, the
ground wires are soldered directly to the coax shield as shown in the following
series of construction photos
|The raw coax from previous designs was
replaces with a premade coax cable with SMA connectors from www.Jameco.com,
part number 163854. I simply snipped off the sma connector on one
end to begin the antenna prep. Other than that, the coax prep for the new
antenna is identical to the last design.. The coax is stripping of
5cm of the outer sheath, and the the shield is trimmed down leaving about
5mm of braid exposed. The exposed shield is then tinned.
|The next step is to prepare the ground
wires. In this photo you can see that I have simply taken two lengths
of 14 guage wire and bend them back on themselves. The overall length
of these bent wires should be about 40mm to give us room to trim later.
You can see how I've overlapped the two wires to create a 'hole' into which
we'll thread the coax. We'll lightly pull the bent wires away from
each other so that the tinned coax shield is trapped in the hole.
Hints: when bending the wire, try
to get the radius of the bend to match the radius of the tinned coax from
the previous step.
|Here's the final antenna. After
trapping the tinned shield of the coax in the loop formed by the overlapping
ground legs, I soldered the legs to each other and to the coax
shield. Then the legs were bent outward to create a star, then downward
to about 45 degrees.
|This is the final antenna . The
ground legs are 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. A small dollup of goop at the base of the signal
wire and also on the coax under the ground legs helps stabilize the antenna.
There is no additional support for the signal wire since I wanted it to
have a little bit of "give" during belly landings of my flying wing.
|That completes the construction of the
revised ground plane antenna!