Where is the source for a 40" MB coax antenna? All I find in the Connection is a 75" length for a quarter wave balun.

Answer:

Antennas don't necessarily need to be resonant and/or efficient. If you have a lot of signal you might not need a lot of antenna. Consider that a marker beacon transmitter may run 50W of power or so into a directional antenna beaming it straight up at your airplane. Now consider that you need to receive it from only a couple thousand feet away at most. It doesn't take a lot of antenna at the receiver to pick up that signal.

Frankly, just about any piece of wire will suffice as a marker beacon antenna.

So, take a piece of coax, strip the shield off of about 40" of it (length is not critical) and connect the other end to your MB receiver. Put the unshielded 40" or so where it might be able to see the ground without too much shielding from the airframe. There is your MB antenna.

Brian Lloyd