wrote:
The BuxComm Antenna Company sells what it calls an All Band Coax-fed
Dipole.

http://www.commparts.com/catalog/pro...ffad91005875fb


It consists of 135 ft. of wire, a balun at the center feed point,

How did you conclude that the feed point is at the center? The lengths
of the sides are labeled only "L1" and "L2" on the drawing.

and
the RG 8X coax transmission line. I don't claim to know a whole lot
about antennas, but this configuration is contrary to everything that I
have read about feeding mutiband antennas. When I wrote to the company
with a question about this, I received a response from K4ABT, Buck
Rogers himself. He attached to his note a section from the ARRL Antenna
Book, which seems to indicate that coax should not be used with this
type of antenna if one wants to use it as a multibander. I have a lot
of respect for Buck, based on his years of Elmering a lot of us through
his articles. But this one has me stumped. Any input will be
appreciated.

I believe the antenna will be quite inefficient on some if not all
bands, either by accident (a balun which becomes lossy when confronted
with extreme impedances) or intent (a resistor inside the "balun"
container). If so, it's possible you'll get a reasonable match on all
bands, and nearly certain that you'll be able to talk to some people
when using it. But it also means that your signal will be considerably
weaker than it would be if you were using an efficient antenna.

Roy Lewallen, W7EL