"Ralph Mowery" wrote in message
nk.net...

"tomerbr" wrote in message
oups.com...
this was a qustion from my instractor in college


As Dave said, there is no ideal length for an antenna.

The 1/4 wave antenna will have a radiation patern that sends much of
the
signal at high angles from it. Not usually good for cell phones
where they
are usually on short towers (if you call a couple of hundred feet
short).
The longer (in wavelengths) antennas tend to put the signal more to
the
horizon and not overhead. By modifying the radiation patern to
put it
more where it is needed instead of where it is not needed you get
gain in
that direction and hopefully longer range.



What an absolute load of blx.

The reason that car cellular antennae are longer than a 1/4 wavelength
is that almost all of them are centre loaded dual antennas or are 5/8
or 7/8 co-linears. The very short ones are often a little longer as
they are coupled through glass and have to be matched.

The wavelength of a signal and it's aerial have nothing to do with the
propagation pattern. A simple VHF or UHF folded dipole for the same
mounting and wavelength related structure spacing radiates the same
shape of pattern irrespective of frequency - roughly apple-shaped in
cross-section.

What you are getting mixed up with is the panel aerials used on most
base station sites. These are almost all multiple stacked element
arrays which are designed to project the signal more outwards and not
down/close in, and they amost always are spaced within the package to
make them directional after a fashion. Many of them have 5 deg or 10
deg of electrical downtilt to give the close-in coverage, hence why
you sometimes see the 'rabbit ears' tilted backwards where range is
important for that particular location.


--
Woody

harrogate2 at ntlworld dot com