>My ELT manual states that if the antenna is being used on an non metallic >surface, such as wood or >fiberglass, A ground plane must also be installed. >The manual does not specify the diameter or size the >ground plane should be.
Generally, a ground plane is 1/4 of the wavelength (or some ODD multiple); for 121.5 MHz, that works out to 24 1/4" (that also happens to be 3/4 wavelength for 243 MHz). The ground plane does not have to be a solid sheet of metal, as little as 3 strips spaced 120 degrees apart will work, 4 strips at 90 is better. RST Engineering ( http://www.rst-engr.com ) sells 1/4" self-adhesive copper tape that works very well. Just be sure to make good electrical contact between the strips and between the strips and the outside (ground/shield) of the antenna. Allen G. Wiesner KR-2S/TD S/N 1118 65 Franklin Street Ansonia, CT 06401 (203) 732-0508 [email protected]
