> > > Do you have any thoughts on why or how a well designed Z
> > > match could produce cable
> > > radiation?
> >
> > For the feedline to radiate, there would have to be currents flowing
> on the
> > shield. It would seem to me the only way to get that to happen would
> be if
> > there was an imperfect shield connection at the mating connector at
> one end
> > or the other. Most Z-matchers I've dissected use a length of wire as
> an L,
> > with shunt trimmer caps. Assuming the enclosure itself is
> bonded well
> to
> > the connectors at either end, I can't come up with a good reason why
> such a
> > device inserted in a transmission line would cause shield
> currents to
> flow
> > absent a connector issue.
> >
> > --- Jeff
>
> How about an instance in which there's a thru hole ground connection
> from the inside to the outside of the case. e.g. a bolt from
> a floating
> pcb ground plane or a capacitor that protrudes thru the case
> & is nutted
> on the outside of the case.
Sure, something like that could cause it, but I've never seen a Z-matcher
built that way using a PC board and a floating ground plane. For the ground
plane to float, it would have to be capacitively coupled to the shield, and
I really don't see why you would ever want to do something like that in a
system using unbalanced transmission lines. If it were inside a PA that had
a floating chassis (such as for operation on either negative-ground or
positive-ground) I could see floating the RF ground off the DC ground
(chassis) inside the amplifier, but once it gets to the outside world, the
RF ground should be the chassis ground in all situations.
--- Jeff
