Help with location of transponder antenna

[[email protected]]

Glider is a Discus 2cT (carbon fuse). Antenna is an external aerodynamic blade style.

Although at some point SH mentioned mounting an antenna on top of the fuse BEHIND the engine bay I have been unable to obtain any drawings or specifications on how to reach this location and it looks like a major PIA to do so..

Assuming there are no details on the rear location mount, my preferred choices would be:

Location 1): On top of the fuse approximately 12" behind the canopy mounted directly in the center. This would be a simple and aesthetically pleasing install but I have not been able to find any data to prove or disprove any health risks by mounting the antenna this close to my (IMO) good looking cranium.

Given the requirement to mount the antenna externally due to the carbon fuse blocking an interior signal from getting OUT, I'm left wondering if the same carbon fuse should then protect me from an external antenna signal coming back IN? (I also heard a rumor that Knoff mounted an antenna in this location on a Duo Discus?)

Location 2: Next to the gear pointing out (down) at roughly 45 degrees. This is again an easy install, astheticaly a little less pleasing being offset at an angle, and once again brings up the question of proximity to my brain.

Thanks so much for any input.

Scott

[Dan Marotta]

I mounted the xponder antenna in your (approximate) location 2 on my
LAK-17a.

There are 3 reasons that I can think of to mount it there:

1. Being on the bottom, you'll be more visible to ATC radar and they will
point you out to any other aircraft under their control or monitoring.
2. Being offset from the center will eliminate the risk of catching the
antenna while loading the glider into the trailer.
3. (At least in the case of the LAK) the fuselage mold join line is on the
center line and the material was too thick to mount the antenna on center.

The ground plane of your antenna, as well as the carbon fuselage, should
shield your good looking cranium (or nuts) from radiation.


> wrote in message
...
Glider is a Discus 2cT (carbon fuse). Antenna is an external aerodynamic
blade style.

Although at some point SH mentioned mounting an antenna on top of the fuse
BEHIND the engine bay I have been unable to obtain any drawings or
specifications on how to reach this location and it looks like a major PIA
to do so.

Assuming there are no details on the rear location mount, my preferred
choices would be:

Location 1): On top of the fuse approximately 12" behind the canopy mounted
directly in the center. This would be a simple and aesthetically pleasing
install but I have not been able to find any data to prove or disprove any
health risks by mounting the antenna this close to my (IMO) good looking
cranium.

Given the requirement to mount the antenna externally due to the carbon fuse
blocking an interior signal from getting OUT, I'm left wondering if the same
carbon fuse should then protect me from an external antenna signal coming
back IN? (I also heard a rumor that Knoff mounted an antenna in this
location on a Duo Discus?)

Location 2: Next to the gear pointing out (down) at roughly 45 degrees. This
is again an easy install, astheticaly a little less pleasing being offset at
an angle, and once again brings up the question of proximity to my brain.

Thanks so much for any input.

Scott

[kirk.stant]

If your concern is being seen by airliners with TCAS, wouldn't' a position on top of the fuselage be at least as good or better during cruise?

While circling, either would be about the same.

Kirk
66

[howdy]

On Tuesday, January 8, 2013 7:45:28 AM UTC-5, kirk.stant wrote:
> If your concern is being seen by airliners with TCAS, wouldn't' a position on top of the fuselage be at least as good or better during cruise?
> While circling, either would be about the same.

> Kirk
> 66


Then what about aircraft climbing from below? Unless we want to install two antennas, one top, one bottom, we have to compromise. TCAS equipped aircraft have top and bottom antennas, but the vast majority of GA aircraft with transponders have the antenna mounted on the bottom.

MK

[Dan Marotta]

I don't generally thermal in the mid to upper flight levels, so airliners
generally aren't a worry. When they're on descent into the Albuquerque
area, they're under the control of Center and Approach. The Feds see me as
well and provide a pointer to the airliners in the event they don't see me.
I periodically call Approach for a transponder check to verify that they see
me. They do.

As to two transponder antennae, I recall from my military days an antenna
switch. It was labelled, Upper-Both-Lower. It was always left in the Both
position. The transponder electronics sensed which antenna was receiving
interrogations and replied on that antenna. Sometimes I flew up side
down...


"kirk.stant" > wrote in message
...
> If your concern is being seen by airliners with TCAS, wouldn't' a position
> on top of the fuselage be at least as good or better during cruise?
>
> While circling, either would be about the same.
>
> Kirk
> 66

[Ventus_a]

Glider is a Discus 2cT (carbon fuse). Antenna is an external aerodynamic blade style.

Although at some point SH mentioned mounting an antenna on top of the fuse BEHIND the engine bay I have been unable to obtain any drawings or specifications on how to reach this location and it looks like a major PIA to do so..

Assuming there are no details on the rear location mount, my preferred choices would be:

Location 1): On top of the fuse approximately 12" behind the canopy mounted directly in the center. This would be a simple and aesthetically pleasing install but I have not been able to find any data to prove or disprove any health risks by mounting the antenna this close to my (IMO) good looking cranium.

Given the requirement to mount the antenna externally due to the carbon fuse blocking an interior signal from getting OUT, I'm left wondering if the same carbon fuse should then protect me from an external antenna signal coming back IN? (I also heard a rumor that Knoff mounted an antenna in this location on a Duo Discus?)

Location 2: Next to the gear pointing out (down) at roughly 45 degrees. This is again an easy install, astheticaly a little less pleasing being offset at an angle, and once again brings up the question of proximity to my brain.

Thanks so much for any input.

Scott

Hi Scott

You can find some info here, http://www.schempp-hirth.com/fileadmin/tmdocs/863-17-2424.pdf

I am given to understand that there is a cost associated with this tech note i.e. pay for drawings etc, but an email to the factory or alternatively the US agents would clear this up

This link is for mounting under the fuse at an angle http://www.schempp-hirth.com/fileadmin/tmdocs/863-4-D-2202.pdf

Cheers
Colin