Jim Lux wrote:
Wayne wrote:
"Spin" wrote in message
...
Wayne........That's interesting.....Can you elaborate on that 2 meter
antenna you had? I wonder if one were to make a longer version would
it have gain & a wider bandwidth?


Sure. However, I'm not recommending it for anything. As I recall it
was a quarter wave of coax terminated in a 10 watt dummy load. The
quarter wave was connected as previously described, with the shield of
the quarter wave connected to the center conductor of the feedline and
the shield of the feedline connected to the center conductor of tthe
quarter wave. I was just trying to get a dummy load to radiate enough
for a short path to a repeater. (Transmitter ran 10 watts)

At a different time, I simply terminated a feedline (low quality
RShack RG-58) with a 10 watt carbon resistor (unshielded and 3 inch
leads). It worked about the same.

However, remember that I was only trying to hit a single repeater, and
a whip antenna with just a few milliwatts would have worked on that
particular path. The "antenna" was very poor, but there may be paths
where it is an acceptable compromise.


Think of this as a variant on taking a 1/4 wave of wire and attaching it
to the center conductor of the feedline (or, just stripping 1/4wave of
shield off the coax) with no choke, balun, or anything else. It's a sort
of sleeve dipole: The "outside" of the feedline coax essentially acts as
the other half of the dipole.

Depending on where it's installed, it might work, might not. No
decoupling means that the whole feedline potentially radiates, etc.
Probably no worse than a lot of other improvised antennas.

Put a really good choke around the coax at the 1/4 wave point, and it
starts to look better, but, having the feedline essentially hanging off
the end of the dipole means that you've got conductors in the high E
field part of the antenna, so there will be capacitive coupling.


Doing the Coro style thing with the resistor, etc, in effect makes this
another of the many "resistively loaded dipole" schemes where you give
up some efficiency in exchange for a better match. No different in
concept (although different in design) from the T2FD sorts of things
from B&W, etc.


I notice Arnie has a terminated, folded dipole or whatever you call it
on his web page. He doesn't offer it as anything other than what it is.
Most of his stuff has always been for people of limited means who still
want to enjoy amateur radio. Cubans are good at that type of thing
because their crappy economic system and the American boycott have
forced them to be that way.
73,
Tom Donaly, KA6RUH