LS-4 Transponder antenna location?

[Matt Herron]

I'm installing a class C transponder in my LS-4, and I'd like to hear
from anyone who's done a similar installation with regard to a few
questions about antenna location. Since the fusilage is not carbon
fiber I intend to locate the antenna internally, and the easiest
placement seems to be way forward in the nose 10 inches or so beyond
the rudder pedals. There's room to attach the antenna and its
reflector plate against an internal panel located on the roof of the
nose with the coax cable led beneath the floorboards back to the
transponder mounted on the instrument panel. The antenna would point
downward from the roof of the nose. It looks like a clean, easy
installation.

Questions:

1) During transmit, the antenna puts out about 175 watts of RF. Is it
going to toast my tootsies, or worse still, give me a bad case of
toenail cancer, or is the frequency such that my feet have nothing to
worry about?

2) There's some metal tubing structure attached to the floorboard
beneath the antenna, probably annodized aluminum, that supports the
rudder pedals and the heel-actuated wheel brake. Will that interfere
with the antenna output?

I'd be grateful for advice. I know from zilch about radios.

[Kilo Charlie]

I don't know zilch about radios either but did install a Becker transponder
and mode C box in my LS-8 last year. I did not place the antenna internally
for the multiple reasons that you listed as potential problems below. I
placed the antenna just aft of the gear doors and slightly off to the side.
It is a fin-type antenna and I have had no problems with it going into the
trailer or being in the way. I also had a thin layer of aluminum placed
inside the fuselage as a ground plane as well as connecting that to the
metal in the rest of the fuselage which I understand is utilized as the
ground plane for the radio antenna. A separate independent battery runs it.
It has worked well although I have not asked the controllers if they can see
me yet.

Casey Lenox
KC
Phoenix

[Gary Evans]

Others have also experienced good results with an internal
mount using the L2 antenna. Its flexable, can be bonded
in place and requires no ground plane. See links below.

http://www.advancedaircraft.com/index.htm

http://www.gliderforum.com/thread-view.asp?threadid=131&posts=18


At 04:12 25 February 2004, Matt Herron wrote:
>I'm installing a class C transponder in my LS-4, and
>I'd like to hear
>from anyone who's done a similar installation with
>regard to a few
>questions about antenna location. Since the fusilage
>is not carbon
>fiber I intend to locate the antenna internally, and
>the easiest
>placement seems to be way forward in the nose 10 inches
>or so beyond
>the rudder pedals. There's room to attach the antenna
>and its
>reflector plate against an internal panel located on
>the roof of the
>nose with the coax cable led beneath the floorboards
>back to the
>transponder mounted on the instrument panel. The antenna
>would point
>downward from the roof of the nose. It looks like a
>clean, easy
>installation.
>
>Questions:
>
>1) During transmit, the antenna puts out about 175
>watts of RF. Is it
>going to toast my tootsies, or worse still, give me
>a bad case of
>toenail cancer, or is the frequency such that my feet
>have nothing to
>worry about?
>
>2) There's some metal tubing structure attached to
>the floorboard
>beneath the antenna, probably annodized aluminum, that
>supports the
>rudder pedals and the heel-actuated wheel brake. Will
>that interfere
>with the antenna output?
>
>I'd be grateful for advice. I know from zilch about
>radios.
>

[Tim Mara]

I think there is some risk from radiation from these antenna's..most
avionics people I have talked with would not suggest mounting the antenna
near any occupants....
for more information on antenna's and antenna installations there is a link
to Comant form my page http://wingsandwheels.com/encoders.htm
tim

"Matt Herron" > wrote in message
om...
> I'm installing a class C transponder in my LS-4, and I'd like to hear
> from anyone who's done a similar installation with regard to a few
> questions about antenna location. Since the fusilage is not carbon
> fiber I intend to locate the antenna internally, and the easiest
> placement seems to be way forward in the nose 10 inches or so beyond
> the rudder pedals. There's room to attach the antenna and its
> reflector plate against an internal panel located on the roof of the
> nose with the coax cable led beneath the floorboards back to the
> transponder mounted on the instrument panel. The antenna would point
> downward from the roof of the nose. It looks like a clean, easy
> installation.
>
> Questions:
>
> 1) During transmit, the antenna puts out about 175 watts of RF. Is it
> going to toast my tootsies, or worse still, give me a bad case of
> toenail cancer, or is the frequency such that my feet have nothing to
> worry about?
>
> 2) There's some metal tubing structure attached to the floorboard
> beneath the antenna, probably annodized aluminum, that supports the
> rudder pedals and the heel-actuated wheel brake. Will that interfere
> with the antenna output?
>
> I'd be grateful for advice. I know from zilch about radios.