Mar - Rcsoaring.com

long as we can get some wire outside of
the fuselage
In this case, I did some improvising. To
extend the wire, we clipped the stock
antenna as short as we could dare to
and still have enough wire outside the
receiver case to make a clean, precision
solder joint. 1/8 inch was enough.
I then soldered a length of shielded
coaxial wire to the stub of the antenna
and placed some heat shrink over the
joint. We now have shielding from the
receiver case on out to whatever the tip
will be. I reinstalled the receiver to the
model in its’ new position and then ran
the new antenna wire out the original
holes in the fuselage. With an abundance
In this photo, we
see the coaxial
wire now attached
to the original
antenna wire and
covered with heat
shrink tubing.
This is an AR9000
receiver by
Spektrum Radio.
of wire hanging out the fuselage, we
then removed the shielding from the
wire that was hanging out, leaving only
a single conductor wire. That wire was
then clipped down to the original antenna
wire length of 32mm, and we proceeded
to perform a standard range check...
perfect! It worked, but will it work in the
air Only one way to find out... fly! And
fly we did. Not a problem and the system
worked perfectly.
Now, I know what you electrical people
are thinking; shielded wire has to be
grounded to work properly. Not in this
case! I have now been flying this model
constantly for the past 18 months and
it has yet to miss a beat. What is not
supposed to work is working perfectly.
But let’s look at what reality says. Theory
says that for a shielded wire to work,
it needs to be grounded. But, all we’re
trying to do here is block the signal
from all but the exposed 32mm worth
of exposed wire. 2.4 signals are indeed
easily blocked, but not by things that
are RF transparent in that frequency
range. We have already proven that trees
and wood are transparent as are most
humans. (There may be exceptions out
there... lots of different people around
this earth.) But in the real world, the
simple grid of wire mesh that is used for
shielding on wire is sufficient to block
the signal on the antenna and allow me
to get away with extending the antenna
at will. I’m not saying this is absolutely
correct and that’s the way to go. The
absolutely right way would, in fact, be to
use a grounded shielded wire and then
have the final 32mm of the wire exposed
for the antenna. A great example of this
is the new JR AR500 receiver.
For the curious people out there, you can
take the cover off of the unit and look at
the antenna connection to the PC board.
You will have to carefully peel back the
silicon glue that holds the antenna to the
Rx board. The longer antenna wire is
attached by a micro connector that has
a core contact and outer shield contact,
indicative of a grounding circuit. (Yes,
you just negated the warranty by digging
in there. Don’t blame me for that!)
26 R/C Soaring Digest