Antenna Emission Patterns

The pictures show the root tube and the front down tube on a Challenger.

Typically, the emissions come from the antenna and the ground plane.  For emissions to the front of the plane, the down tube makes the ground plane.  For backward transmissions, the root tube makes the ground plane.

In the lower picture, the typical back-leaning antenna would put out its strongest emissions to the rear.  To the front, the emissions are spread over a much wider arc making them weaker at the receiving antenna.  To make matters worse, much of the emissions are broadcast skyward.  This isn't so good for contacting an airport or aircraft you are approaching.

In the upper picture, the same antenna mounted so it leans forward will concentrate its forward emissions nearer the horizon.  This will greatly improve, maybe double or more, the range of the radio when tracking inbound to an airport. Ability to contact an airport directly to the rear is reduced.

Though it's not shown, a vertical antenna will split the difference.

I am not an antenna design engineer.  These are simply the procedures I learned when I was an Army Reserve communications sergeant and from my short bout with amateur radio -- I like designing field expedient directional antennas to improve radio range.  This let us avoid moving our headquarters so often and I hated moving the headquarters with all the tear-down and set up work involved.

If there are antenna design engineers or advanced radio amateurs with better info, please contact me and I'd like to learn more.  ed@edburkhead.com