Does a 5/8 wave antenna need a metal ground plane?
 

I know that a 1/4 antenna needs one to work but do 1/2 and 5/8 ant. need
a metal gnd plane.
Or will they work on a wooden building?

bbnn wrote:
"I know that a 1/4 antenna needs one to work but do the 1/2 and 5/8 ant
need a metal ground plane?"

A radio has a pair of RF signal connections. It isn`t the length of the
antenna which determines the need for a counterpoise. Balanced antennas
have a pair of connectors. These are interchangeable and may be
connected to the radio`s pair of RF connections. If the transmission
line wires are close-spaced, they don`t tend to radiate much.

An unbalanced antenna works against the earth, a ground plane, or a
counterpoise. It may have only one insulated connector. But the radio
requires two RF connections to make a complete circuit. The unbalanced
antenna needs a connection between the grounded side of the radio, or
one of the ungrounded RF terminals if there is no grounded terminal, and
the side of the antenna meant for a ground connection, such as its
ground-plane. This connection frequently is made by a coax`s external
shield.

If you have an unbalanced antenna, it needs something like a ground
plane so that you have something to connect the grounded side of your
radio to for a complete circuit. Otherwise the transmission line becomes
part of your radiator.

A balanced antenna, such as a dipole or a loop, has interchangeable
terminals and needs no connection to the earth for a complete RF signal
path. A ground plane would be superfluous.

Best regards, Richard Harrison, KB5WZI

A 1/2wl antenna theoretically does not need one because of current
distribution...a 5/8wl on the other hand, does...
(personally, I use a gp on a 1/2wl anyway ;)
On a 5/8wl antenna, use a ground plane...at least (4) 1/4wl radials in
length at 90deg to each other. For max performance, the antenna should be in
the center of a solid metal ground plane at least [1.5*(1/4wl of freq)] x
[the same amount]...on 2m, that would be 28 x 28 inches

Chris
WB5ITT


"bbnn" wrote in message ...
I know that a 1/4 antenna needs one to work but do 1/2 and 5/8 ant. need a
metal gnd plane.
Or will they work on a wooden building?