ASW-24 - Transponder Cable Routing in Fuselage

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