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.