Ed_Greenberg@3mail.3com.com (05/08/91)
A previous poster commented that the short stubby antenna on a handheld
cellular phone is a helically wound 1/4 wave, rather than a 1/8 wave as
had been previously posted. He asked for confirmation.
I don't think it would unwind to an exact quarter wave, but it would be
about right, and it will be the correct length for the best possible
match, which is what is desired. Unfortunately, as a vertical antenna,
it needs a ground plane, and it doesn't have one. Thus it won't be all
that efficient.
A much better antenna for a handheld is the six inch or so jobbie that
is fat for the lower half and thin for the upper half. What we have
here is a center-fed, half-wave, vertical dipole, drawn below
horizontally:
<---- down to radio // up to sky --->
--------------------------\
===============================+-------------------------
--------------------------/
The === represents feedline, and the center of the feedline is connected
to the upper (rightmost) radiator. The shield of the feedline is
connected to the lower (leftmost) hollow section, at the center.
This antenna will be much more efficient than the stubby one, since the
lower section of the dipole acts as a ground counterpoise
Considering the fact that you've got .6 watts and you're trying to make
it out of the shopping center half the time, the best thing you can do
for your cellular service is a good antenna.
-edg
Ed_Greenberg@hq.3mail.3com.com