Meindert --

I generally agree with your statement regarding shields.

The question I have, though, is as follows

Given that the ground for an SSB antenna carries a lot of RF current, and
given that all grounds end up tied together at some point aboard a vessel,
by leaving the shields ungrounded at one end, isn't there a risk of creating
a parasitic antenna out of your signal shields.

I have heard reports (not my experience) of the AC safety grounds being
capacitively tied back to ground at their other end to avoid this problem.

I would think this would only be a problem where the cable approximated a
quarter wavelength - which might explain why I have only heard this problem
reported on AC grounds, which could grow to be pretty long.

Has anyone else in the group experienced such a problem, and if so, what did
they do to correct it?

Dave Morschhauser


"Meindert Sprang" wrote in message
...
"Larry W4CSC" wrote in message
...
I'd rather see shielded connectors so I can run shielded pair cables and
RF
bypassing of all inputs to keep the HF SSB from screwing all the NMEA
crap
attached to it. Shielding everything would also make it so we could
HEAR
the HF receiver and get our WEFAXes without the constant drone of NMEA
radiated interference from all the unshielded, unbalanced connections
with
just open wires sticking out of things. NMEA needs to get its act
together
and enforce some standards on its members....

Funny thing is: you don't need shielded connectors to be HF-quiet. The
physical size of two screw terminals and an inch of bare wire ends are
simply not enough to be able to radiate sufficient RF. What does radiate
on
HF are long cable runs that are either unshielded or unbalanced. Raymarine
have put our multiplexers to the test to comply with IEC945 for instance,
which limits for susceptibility and emission are rougly ten times more
stringent than FCC Part 15 class B. And it passed that test while being in
a
plastic box and having screw-terminals. The really important thing is to
have it wired correctly and, most important, not to connect a shield *at
both ends*.

Meindert