On 12 Nov 2006 15:11:40 -0800, "Paladin" wrote:

Hello "Antenna-Lovers",
How do dual-band antennas work? I bought a COMET
"SSB-7" antenna for my mobile radio. It worked great for a year or more
and then,trouble. I don't know "HOW" to trouble-shoot it.
Where on the antenna can I check for "continuity" or somewhere I can
look to find a "fault" of sorts.
It costs a bit more than a lower gain antenna. How can I trouble-shoot
it ?

Don't know about the Comet mobile antenna but I've been using the
Diamond series since they came out. The one on my car (4-Runner) has
hit so many trees and been straightened so many times it's beginning
to look strange. It's also worn to the point where it no longer seats
well at the fold over point. (I had to use some lapping compound on
it about two years ago to keep it from rattling). It looks like I'm
going to need to redo it at the fold over point again.

I have used the Comet duo band base station antennas with good luck
except for the one that took a direct lightning strike. Part of the
inside disappeared, the top two feet of fiberglass looked like an
exploded cigar, and the matching network at the base was shorted. The
base station antennas are well built and I'd have though the mobiles
would be the same, but apparently not.

Actually I have two Comets and one Diamond base station antennas for
144 and 440. I also have stacked pair of 11L on 440 and 12L on 144 at
130 feet. The Diamond is at 50 feet and one Comet is at 15 feet which
is the one I normally use for repeater work. The second Comet is going
to be mounted inverted under the Diamond and used for packet/jnos.

As to servicing the duo-band mobiles, there's not much to do. The
problem could be in the mount, but most likely it's either in the
molded base, or in the phasing sections. Most of these use something
that looks like a plastic insert between sections. Inside that insert
will be either a coil or a folded piece of wire that looks a lot like
a paper clip. These serve different functions on 144 and 220. Still
they either work or don't. Typically about the only thing that can go
wrong is a connection or solder joint. *Sometimes* they get some
corrosion down where the antenna fits into the base section. It is
held with one or two Allen set screws. Road salt can wreak havoc in
these areas.



73's Paladin
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com