Antenna Install in a Metal Glider

On Apr 9, 2:14*am, Markus Graeber wrote:

Thanks Bob, I was actually thinking about the possibility
of installing the antenna in the rudder since it has fabric
cover...

As others have said, that probably will not work very well. The metal
frame of the rudder will interfere with the antenna's radiation
pattern, and it will probably have an unacceptably high SWR (standing
wave ratio).

The other more extreme option could be to replace the
vertical stabilizer leading edge aluminum panels with fiber
glass but that might have some structural side effects
and I am not sure how much aluminum ribbing will affect
an 1/4 wave antenna install.

I think that will not work very well either. It would require a non-
trivial structural analysis to make sure that there is adequate
torsional and bending stiffness in the absence of the metal skin of
the modified areas.

I suppose that you could develop a composite (fiberglass or aramid,
but not carbon) rudder for the Lark and put the antenna inside of
that. But in the overall scheme of things, the effort is great and the
payoff is rather modest. You are probably a lot better off just
installing the bent 1/4-wave whip antenna and investing your time and
money on more productive endeavors.

Thanks, Bob K.



Certification wise it's not a problem since gliders are treated here similar to experimentals in the US...

Markus

I suppose that you could develop a composite (fiberglass or aramid,
but not carbon) rudder for the Lark and put the antenna inside of
that. But in the overall scheme of things, the effort is great and the
payoff is rather modest. You are probably a lot better off just
installing the bent 1/4-wave whip antenna and investing your time and
money on more productive endeavors.

Thanks, Bob K.



wait isn't the rudder on the IS28-B2 fabric covered?

On Apr 9, 7:50*pm, Tony wrote:

wait isn't the rudder on the IS28-B2 fabric covered?

Yes, I believe it is fabric on an aluminum frame. If that is so, the
metal frame will disrupt any sort of internal antenna, an antenna
placed between the fabric and the fabric cover, and even an antenna
glued to the outside of the fabric.

Thanks, Bob K.

On Apr 9, 10:19*pm, Bob Kuykendall wrote:
On Apr 9, 7:50*pm, Tony wrote:

wait isn't the rudder on the IS28-B2 fabric covered?

Yes, I believe it is fabric on an aluminum frame. If that is so, the
metal frame will disrupt any sort of internal antenna, an antenna
placed between the fabric and the fabric cover, and even an antenna
glued to the outside of the fabric.

Thanks, Bob K.

How about a retractable 1/4 wave antenna? I seem to recall some HP's
with them back in the '60's.

Alternatively, a rubber ducky from a handheld mouonted under the
fiberglass fairing over the wing root just might work well enough for
1 - 5 mile local talk. Sparkies will have to explain if that would
work.

Here is a link to the retractable antenna/TE probe Bill mentioned.
http://www.soaridaho.com/Schreder/Co...E_ANTENNA.html

Wayne


"Bill D" wrote in message
...

On Apr 9, 10:19 pm, Bob Kuykendall wrote:
On Apr 9, 7:50 pm, Tony wrote:

wait isn't the rudder on the IS28-B2 fabric covered?

Yes, I believe it is fabric on an aluminum frame. If that is so, the
metal frame will disrupt any sort of internal antenna, an antenna
placed between the fabric and the fabric cover, and even an antenna
glued to the outside of the fabric.

Thanks, Bob K.

How about a retractable 1/4 wave antenna? I seem to recall some HP's
with them back in the '60's.

Alternatively, a rubber ducky from a handheld mouonted under the
fiberglass fairing over the wing root just might work well enough for
1 - 5 mile local talk. Sparkies will have to explain if that would
work.

On 4/10/2012 12:32 PM, Wayne Paul wrote:
Alternatively, a rubber ducky from a handheld mouonted under the
fiberglass fairing over the wing root just might work well enough for
1 - 5 mile local talk. Sparkies will have to explain if that would
work.

First, It must be said that a rubber ducky is inferior to a properly
installed 1/4 wave antenna. Exactly how inferior depends on the
construction of the individual ducky (since they come in various heights)

That said, most of the communicating I have done from gliders has been
with hand-helds with rubber ducky antennas. For local communications,
they've always worked great for me. It's my opinion that a nicely
installed rubber ducky on a proper ground plane will do better than that
same rubber ducky tacked to the top of a portable radio. In lots of
gliders, there are places where you could mount a rubber ducky under the
canopy and have a short transmission line (to help mitigate some of the
loss) and zero drag penalty.

Vaughn