ASW-24 - Transponder Cable Routing in Fuselage

The Schleicher web site indicates a transponder antenna should be installed in the landing gear bay. Of course it is in German, but even with Google translate it does not seem to indicate how to snake the antenna cable form the transponder behind the instrument panel to the landing gear bay. Does anyone have a suggestion how to route the cable? I see the various electric and pneumatic lines running forward to the nose and down through the bottom of the fuselage, but it looks very difficult (impossible?) to snake a line though the same location. Any help would be appreciated.

Thanks,

Lauren
5YA

On Monday, February 2, 2015 at 5:01:45 PM UTC-8, wrote:
The Schleicher web site indicates a transponder antenna should be installed in the landing gear bay. Of course it is in German, but even with Google translate it does not seem to indicate how to snake the antenna cable form the transponder behind the instrument panel to the landing gear bay. Does anyone have a suggestion how to route the cable? I see the various electric and pneumatic lines running forward to the nose and down through the bottom of the fuselage, but it looks very difficult (impossible?) to snake a line though the same location. Any help would be appreciated.

Thanks,

Lauren
5YA

Of the two positions they show I would be installing the transponder behind the gear well doors, the other one is well around the side of the fuselage and too horizontal for my liking.

Which Transponder? One of the advantages of a Trig TT-21 or TT-22 is being able to place the transponder box near the antenna and only have to fish the control head wiring up to the panel, no RF coax. If you have not purchase a transponder yet this is one good reason to go with a Trig or other transponder that mounts this way.

There are frequently no great choices for routing RF coax cables with pivoting canopies, if the cable bundles/flex conduit/brading/heatshrink are loose then you can fish a cable though them, but if not your options are tying/binding the cable to the outside or cutting it open and re-secure the bundle again by alternate means, or undoing everything and pulling it through a new flex braiding tubing or similar. I really dislike the excessive use of heatshrink on these pivoting panel installs. but if I cut open a typical one I'd be there for a week replacing every piece of wiring. Make sure you are using the correct RF coax (1GHz transponders are a lot less forgiving to cable and connector issues than 100MHz VHF radios). If using a 1/4 wave antenna as Schleicher describes make sure you install a proper ground plane. Schleicher instructions for other glider models will show you clearer pictures/instructions of things like a proper ground plane.

On Monday, February 2, 2015 at 8:01:45 PM UTC-5, wrote:
The Schleicher web site indicates a transponder antenna should be installed in the landing gear bay. Of course it is in German, but even with Google translate it does not seem to indicate how to snake the antenna cable form the transponder behind the instrument panel to the landing gear bay. Does anyone have a suggestion how to route the cable? I see the various electric and pneumatic lines running forward to the nose and down through the bottom of the fuselage, but it looks very difficult (impossible?) to snake a line though the same location. Any help would be appreciated.

Thanks,

Lauren
5YA

The tech note shows a position that is next to the landing gear box on the right side. The antenna mounting and ground plane are installed through the oxygen cylinder area. This is an easy installation but not as technically perfect as it is if you install on the bottom behind the gear. It also takes about 1/4 of the time to do.
UH

A single coax may be easier to fish
through than at least 6 wires between a
Trig head and remote plus + & - to the
remote plus optional gear position and
GPS.

Hint: Don't bother ordering a coax with
both connectors on as highly unlikely to
get through the tight spaces.

I've been thinking / fantasizing of using a
carbon fiber tube to get the coax to the
fin battery box where an L2 antenna could
fit. You need one stiff enough to take the
G's while glued in only at the ends

Is this totally crazy or vaguely possible?

On Monday, February 2, 2015 at 9:00:07 PM UTC-8, George Haeh wrote:
A single coax may be easier to fish
through than at least 6 wires between a
Trig head and remote plus + & - to the
remote plus optional gear position and
GPS.

You would normally use about half of the pins on the controller head B-9 connector used and yes its often going to be easier to fish those, than a RF coax cable, but more importantly a coax, even a semi-flexible one does not enjoy being flexed in use. And the Trig transponders are designed to have relatively short cable runs between the RF box and the antenna. With a TT-21 main box mounted in a glider panel and a long coax run to the tail, you are increasing the possibility that install will fail a RF output power test.

You may have issues with the length of your coax run the tail battery box. I don't know how you would secure your tube in place and you don't want it flexing and telegraphing any mechanical movement into the cable. also be careful of things like shielding of the transponder signal by the tailplane or other carbon fiber parts. The good old boring downward pointing 1/4 wave stub antenna placed somewhere roughly behind the main gear with a proper ground plane works *very well*. Most L2 antennas are installed inside the tail boom of fiberglass fuselage gliders, not way back in the fin. More modern fin/hinge line mounted transponder installs down by glider manufacturers are very careful about using premium low-loss cable.

On Monday, February 2, 2015 at 8:40:01 PM UTC-5, Darryl Ramm wrote:
On Monday, February 2, 2015 at 5:01:45 PM UTC-8, wrote:
The Schleicher web site indicates a transponder antenna should be installed in the landing gear bay. Of course it is in German, but even with Google translate it does not seem to indicate how to snake the antenna cable form the transponder behind the instrument panel to the landing gear bay. Does anyone have a suggestion how to route the cable? I see the various electric and pneumatic lines running forward to the nose and down through the bottom of the fuselage, but it looks very difficult (impossible?) to snake a line though the same location. Any help would be appreciated.

Thanks,

Lauren
5YA

Of the two positions they show I would be installing the transponder behind the gear well doors, the other one is well around the side of the fuselage and too horizontal for my liking.

Which Transponder? One of the advantages of a Trig TT-21 or TT-22 is being able to place the transponder box near the antenna and only have to fish the control head wiring up to the panel, no RF coax. If you have not purchase a transponder yet this is one good reason to go with a Trig or other transponder that mounts this way.

There are frequently no great choices for routing RF coax cables with pivoting canopies, if the cable bundles/flex conduit/brading/heatshrink are loose then you can fish a cable though them, but if not your options are tying/binding the cable to the outside or cutting it open and re-secure the bundle again by alternate means, or undoing everything and pulling it through a new flex braiding tubing or similar. I really dislike the excessive use of heatshrink on these pivoting panel installs. but if I cut open a typical one I'd be there for a week replacing every piece of wiring. Make sure you are using the correct RF coax (1GHz transponders are a lot less forgiving to cable and connector issues than 100MHz VHF radios). If using a 1/4 wave antenna as Schleicher describes make sure you install a proper ground plane. Schleicher instructions for other glider models will show you clearer pictures/instructions of things like a proper ground plane.

I purchased a used Becker 3401-1-R (due to cost considerations). I want to use an L2 antenna. The transponder has a remote head, but I plan on putting the transponder box and encoder in the area behind the instrument panel. I was originally going to put the antenna behind the instrument panel, but I read a few posts and decided that was a bad idea due to the output of the antenna. The transponder antenna cable is a BNC to BNC, so I was going to get a cable with one end and snake it to the landing gear box and then crimp on the other end.

Thanks for the feedback,

Lauren

On Monday, February 2, 2015 at 5:01:45 PM UTC-8, wrote:
The Schleicher web site indicates a transponder antenna should be installed in the landing gear bay. Of course it is in German, but even with Google translate it does not seem to indicate how to snake the antenna cable form the transponder behind the instrument panel to the landing gear bay. Does anyone have a suggestion how to route the cable? I see the various electric and pneumatic lines running forward to the nose and down through the bottom of the fuselage, but it looks very difficult (impossible?) to snake a line though the same location. Any help would be appreciated.

Thanks,

Lauren
5YA

Per the trig manual the cable max cable length for RG 400 coax is 8'4". I believe the manual is fairly conservative on the lengths of cable. The RG400 is a dual shield coax about .200" in diameter. It is stiff and should be fairly easy to string the cable without the Coax connector, but you would need a crimp tool to install the connector. The transponder end uses a TNC and the antenna end a BNC.

The cable for connecting the components is two .120 dia shielded cables, with a DB9 on the Head and a DB15 on the transponder with a power & Ground. Stringing these in my opinion would be just as hard and then you would have to solder or insert 6 wires in the DB9 and the hood. I sell these cables generally with a 2' length.

Most install the transponder in front of the panel and the antenna behind the gear at an angle so when you slide the glider in the trailer you don't damage it.


Richard
www.craggyaero.com