ADS-B Antenna proximity

[Ed Haywood]

I have a tube and fabric aircraft, so there are limited surfaces with a ground plane suitable for mounting an antenna. I have one of those 3 inch ball-and-stick antennas mounted on my belly pan. It is connected to my GTX-335 transponder, so I assume it is for ADS-B Out.

I would like to add an antenna for ADS-B In to improve ground station reception by my Stratux. It is my understanding that the belly of the plane is the best place for that. Can I mount a second ball-and-stick antenna to the belly pan, or do I need to look elsewhere?

 

[flyingron]

That should be fine. The wavelength on these things are short (roughly 11 inches) so that separation will work fine. I've seen transponder and DME antennas closer.

 

[Jesse Saint]

That should be no problem.

 

[Daleandee]

On the belly of my experimental I have two of the small transponder antennas. One is for my Garmin 320A and the other is for my Echo ADSB out. They are required to be 40" apart. For your installation I agree with the others that it should not matter as only one of your antennas will be transmitting.

But having said that I would separate them as much as is reasonably possible.

 

[geezer]

There are resonant distances, and anti resonant distances.

A good avionics installer can tell you exactly how far center to center is a the optimum anti resonant distance, and the multiples of it.

Use the largest practical multiple. Somewhere near the red arrow should be in the ballpark, but an inch either way might be much better, or worse.