"bpnjensen" wrote in message
...


I don't think the windshield-internal dipoles work as well on FM as a
good external vertical whip of the proper dimension. They are not
omnidirectional, nor are they vertically polarized, both of which are
helpful for FM in a moving car. The folded ones may have different
characteristics that overcome these drawbacks, I don't know for sure.



Moreover, they are not likely the AM antennas at all - almost every
car AM radio since dirt has used a ferrite- or air-core coil antenna;
far more effective than a whip or wire ever could be. Especially the
ferrite, it gets you what a whip cannot - ~ full wave resonance and
high relative gain. Match that with a quality AM radio and you'll
have a nice MW DX machine in your car. I love listening to stations
on the Great Plains when driving overnight to Yellowstone :-)

Bruce Jensen


1) Those were not dipoles. The use of two wires was for symmetry purposes
only. They were not directional at all.

2) The only AM car radios that ever used a loop or loopstick antenna were
the "pull-out" portables. Almost every car radio ever made (up until
digital readout synthesized units) used variable inductors for tuning, but
for tuning only, because they were more stable than variable capacitors.
The antenna was and has always been that whip on the fender/cowl/windshield.
These are far more effective than a loop or loopstick in an automobile,
since those type antennas do not work at all well inside a steel structure.
I guarantee you that if you unplug that whip from your car radio, it will go
silent (unless you are sitting next to the transmitter site.)