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Quarter-wave for aviation communication frequencies is about two
feet... something like that. (I'll let all the experts jump on that
one :-) So I suggested he replace the rubber ducky with a quarter-wave
and see if that didn't help.

Close enough. With brazing rod, it is closer to 22.5", but what the hell.
Most likely he will be staying down in the bottom end of the band anyway, so
23-24" should work just fine.



When the feller got the BNC connector (eighty cents but he had to send
away for it) he sees that the center pin is smaller than the brazing
rod. In fact, the center pin is about .050" whereas the brazing rod
was an honest sixteenth of an inch. (The idea here is that the brazing
rod REPLACES the center pin.) Now, the truth is, a BNC connector --
the female part -- is more than willing to accept a .0625" dia pin,
assuming you put a bit of point on it and don't just jab it in there.
But he was afraid of ruining the connector on his belly pan so he came
by the shop and asked if I'd turn down the brazing rod to match the BNC
connector.

An alternative method (and one that is a little easier on the center pin of
the mating female connector) is to turn the brass rod down at the end to the
diameter of the center conductor of RG-58 coax so that it fits into the
little hole in the end of the pin that comes with the connector.

Just about a tenth of an inch turned down to 0.025 or so will work just
fine, thank you, and you can do it with either a file or a grinding wheel.
Just so it sticks into the little hole in the end of the pin a short ways.

While you are at it, grind a little bit off of the brass rod a half-inch up
from the pin end. Not too much, now, just a few thousandths and about a
tenth of an inch long. The edge of the grinding wheel will be just fine, or
a rat tail file will work also. It doesn't have to be square -- rounded is
actually a little bit better. Sort of like the old coke-bottle shape.

Now put that ground down rod end into the center pin and solder it without
getting solder all over the business end of the pin. Stuff the pin into the
connector body until the pointy end of the pin is flush with the bottom of
the connector.

Now mix you up some of that good epoxy and fill the open end of the
connector (the part that has the brass rod sticking out of it) up to the
top. Why did you grind that little dipsy-doodle into the rod? So that if
the epoxy loosens up with the rod over time that the rod won't depart the
airframe and do great damage to landlubbers. Don't worry about it loosening
up with the connector body. That's what the threads that would have held
the jam nut are for. THe epoxy will fill those threads AND the dipsy-doodle
and bind them tight together.

(My Rat Shack still has BNC connectors; yours may have gotten rid of the
small parts.)

Jim