Maybe this has been covered in RAS but I couldn't find it. I looked through two documents about the spacing of FLARM antennas, specifically the FLARM A and ADS-B antennas. Obviously, the thing to avoid is the transmitting of FLARM data (A antenna) interfering with ADS-B (or GPS) reception.

The FLARM document "PowerFLARM_Application_Note_ANTENNAS1.pdf"* has the following information about antenna spacing. It doesn't mention a minimum distance between the FLARM A and ADS-B antennas;

Keep antennas separated as far as possible!
Min. distance between RF antenna on FLARM A and FLARM B port: 1ft (0.3 m)
Min. distance between RF antenna on FLARM A port and GPS antenna: 1ft (0.3 m)
Min. distance between RF antenna on FLARM B port and GPS antenna: 4in (0.1 m)
Min. distance between ADS-B / XPDR antenna and GPS antenna: 4in (0.1 m)

The FLARM Core V2.0 manual** says the following in the section on ADS-B antennas;

"This antenna should be placed at least 30cm/1ft away from the FLARM antennas. The FLARM antennas have priority over this antenna for best placement."

1 foot (30cm) spacing within our tight glider cockpits is going to be a struggle. Based on the FLARM portable (might not be the best example) the two antennas are only 2.5" (0.06 m) apart.

Anyone have more information on this spacing conundrum?

Thanks, John "OHM"

* http://cumulus-soaring.com/flarm/Pow..._ANTENNAS1.pdf. I don't see it on the FLARM.org web site. Was it superseded?

** https://flarm.com/wp-content/uploads...anual-2.00.pdf