Crazy George wrote:
. . .
Loops respond to magnetic fields, and dipoles respond to electric fields. . .

That's not at all true. Both kinds of antennas respond to both electric
and magnetic fields.

An *electrically small* loop responds more strongly to a magnetic than
an electric field only if the source of the field is much closer than a
wavelength. Likewise, an *electrically small* dipole responds more
strongly to an electric than a magnetic field only if the source of the
field is much closer than a wavelength. At some distance from the source
still less than a wavelength, they actually reverse -- the short dipole
responds more strongly to a magnetic field than a small loop, and the
small loop responds more strongly to an electric field than a short dipole.

The response of electrically large (on the order of a half wavelength
and larger) dipoles and loops to electric and magnetic fields depends on
the direction and distance to the source. No single rule of thumb can be
used when the source is very close to anything but an electrically small
antenna. The relative responses of *all* antennas to electric and
magnetic fields are essentially the same as each other if the source is
a fair fraction of a wavelength away (i.e., the antenna is in the far
field of the source).

Roy Lewallen, W7EL

Roy, W7EL wrote:
"The response of electrically large (on the order of a half wavelength
and larger) dipoles and loops to electric and magnetic fields depends on
the direction and distance to the source."

Yes. The dierectional response of a 1/2-wave folded dipole is the same
as that of a 1/2-wave open-circuit dipole. The main difference may be
the difference in impedance presented to the transmission line.

Here is my experience. Lightning is an extremely large noise. My
corporation used VHF radios to interrogate remote data stations. For
decades we used Andrew Corporation folded 1/4-wave unipoles atop high
towers around the world in base stations to communicate with mobiles in
any direction. These had proved indestructable. Both the stainless steel
antenna and the radio used, with no lightning protection on the
feedline, other than the Heliax used to connect the antenna with the
radio. This was before we started the data radio operation. The Heliax
is a common-mode rejecter due to its equivalent circuit.

For the data radios, the operation was point-to-point. Directional
antennas were useful in this service. The data radios immediately
started to be destroyed by lightning strikes. Problem was the yagi
antenna. The driven element was an open circuit. We quickly fixed that
with an short-circuit 1/4-wave stub shunted across the antenna at its
feedpoint. No more lightning damage. The short-circuit removed enough of
the off-frequency noise (lightning) to save the radios. So the operation
continues decades later with Motorola transistorized mobile radios as
the data base and remote stations.

Best regards, Richard Harrison, KB5WZI