GPS anetenna location OK in baggage area of a fiblerglass glider?

Two questions;

Dirk_PW - What glider do you own? Do you know if it is fiberglass or carbon fiber? They all look the same on the outside, you know! As Paul says, fiberglass will allow GPS reception but carbon will not.

Darryl - I was unaware that "many" (!) CF gliders have this RF transparent area behind the pilot's head. That would be great as an optional area for mounting antennas as behind our panels things are getting pretty full these days. Any idea which brands/models have this feature? Schleicher ASW-27 by any chance?

PS - Darryl mentions concern about too long of a length of the coax on the GPS antenna. I would suspect, and hope, that the manufacturer wouldn't sell a GPS antenna with an overly long coax. The proof would be in the pudding I suppose - before you go to all the trouble of routing the coax fore to aft, test the functionality with all the coax laying out on the floor. BTW, shortening the tiny GPS coax, and fitting a new tiny connector to it, is much more difficult than a simple BNC.

Best of luck, John Ω

Thanks.

It's not a problem to shorten the coax.Â* Simply open the antenna puck by
peeling off the sticker on the back and removing the screw(s).Â* The coax
cable is soldered conveniently in front of you and it's an easy thing to
remove it, cut and strip it to length, and solder back into place.Â*
Replace the cover and you're done.

Hmmmmmmm...Â* Regarding my previous post - maybe there's a problem with
my Flarm antenna since I shortened the coax.Â* I'll swap that one out
first as a test.

On 2/26/2018 6:59 AM, OHM Ω http://aviation.derosaweb.net wrote:
BTW, shortening the tiny GPS coax, and fitting a new tiny connector to it, is much more difficult than a simple BNC.

Best of luck, John Ω

Thanks.

--
Dan, 5J

maanantai 26. helmikuuta 2018 16.00.04 UTC+2 OHM Ω http://aviation.derosaweb.net kirjoitti:
I was unaware that "many" (!) CF gliders have this RF transparent area behind the pilot's head.

Well there is not, this is simply not true. Some level of satellite reception is possible trough canopy to that area. Only RF transparent area is usually at tail where VHF antenna is mounted.

On Monday, February 26, 2018 at 6:40:27 AM UTC-8, krasw wrote:
maanantai 26. helmikuuta 2018 16.00.04 UTC+2 OHM Ω http://aviation.derosaweb.net kirjoitti:
I was unaware that "many" (!) CF gliders have this RF transparent area behind the pilot's head.

Well there is not, this is simply not true. Some level of satellite reception is possible trough canopy to that area. Only RF transparent area is usually at tail where VHF antenna is mounted.

Every glider I've seen has white glass, not carbon, in the turtle deck. White glass is highly transparent to RF in that frequency range. You can check by putting a very strong light on the outside and see if the inside glows. It will through white glass, not through carbon. Sometimes it is covered with paint which makes it harder to tell (the light will penetrate the outside gel coat).

Within reason, you can have a pretty long coaxial cable on a normal GPS antenna. They have a 26 - 30 dB amplifier in them, so the signal from the antenna to the device is not weak. That is also the reason they can interfere with other GPS antennas and devices - if not well shielded and grounded, they become a transmitter themselves. Make sure if you shorten the cable at the antenna end that you get a good solder joint on the shield (easy to get a cold joint here because of the ground plane in the board). Another way to shorten the cable is to cut the other end and crimp on a new coaxial connector. The Flarm uses an MCX.

On Monday, February 26, 2018 at 6:40:27 AM UTC-8, krasw wrote:
maanantai 26. helmikuuta 2018 16.00.04 UTC+2 OHM Ω http://aviation.derosaweb.net kirjoitti:
I was unaware that "many" (!) CF gliders have this RF transparent area behind the pilot's head.

Well there is not, this is simply not true. Some level of satellite reception is possible trough canopy to that area. Only RF transparent area is usually at tail where VHF antenna is mounted.

I'm not sure which cereal box you are reading to get all your knowledge, but you might want to consider switching brands.

maanantai 26. helmikuuta 2018 19.49.54 UTC+2 Darryl Ramm kirjoitti:
On Monday, February 26, 2018 at 6:40:27 AM UTC-8, krasw wrote:

I'm not sure which cereal box you are reading to get all your knowledge, but you might want to consider switching brands.

Please refer to make and model of glider where the fuselage is carbon with glass turtle deck?

Name one where it is not. Go do the light test Jon discussed. Every Schleicher fueslage I have looked at is this way. Pretty sure the DG1000 is, ...

You were claiming no glider fuselages have this, having used GPS antennas mounted under the turtleneck in several otherwise carbon fiber glider fuselages I know you are wrong about that.

Here is a game for the upcoming SSA convention... folks there can ask or look to check if the turtledecks in all the gliders on display are RF transparent or not.

Oh the anticipation for the advancement of human (well r.a.s.) knowledge is killing me.... :-)

Dude, please don't die.......

While I hope you have some replies copied to a text file so you can, "copy paste" to cover things that have been asked many times (yes, on some car forums I have "canned replies" in a text file, just copy paste as an answer), I hope you stay around.

Maybe that is a kiss of death.......;-)

If you are fortunate enough to own an SZD 55-1, mount the FLARM in the tail battery box. Bond the FLARM antenna to the vertical stab just below the metal parts of the horizontal stab. Bond the ADS-B antenna to the vertical stab just above the rudder counter weight. Makes for very short antenna leads. Use the existing battery cables to power the FLARM from a new battery box mounted to the stbd side of the main gear box. Now for the hard part, fish a data cable forward to the FLARM display of your choice.

maanantai 26. helmikuuta 2018 21.12.23 UTC+2 Darryl Ramm kirjoitti:
Name one where it is not.

Sorry but with "light test" you have no clue of the turtle deck material. Why an earth would factories go trough massive pain and expense of laying up turtledeck using different material instead of just rolling up carbon/kevlar? Instruments and their antennas tend to reside in the instrument panel. Routing GPS antennas to behind pilots back, who does this, and why would factories be interested in this? Please give some reference to glass turtledeck in carbon fuselage, anything will do. RF transparence is different thing, antenna on the hat shelf sees sky trough canopy as I stated earlier.