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On 7 Sep 2003 20:22:34 GMT, Too Much SPAM (ckh) wrote:

Or it could mean that you keep a backup, inexpensive solid state
rig in a metal box. It could be anything, an old Tentec, an
IC-701, anything will work.

My so-far-limited research indicates that probably wouldn't be good
enough. You'd have to have more than just a thin metal box, maybe a
THICK metal box, or lead, or something, and perhaps there'd be
grounding considerations.

If you planned for it, you could have a spare set of diodes in the
impervious metal box and just sub them in when the balloon goes
up.

True, I thought of that, and it's one of the options.

Anyway, I'm guessing that the EMP risk is overstated.

I would like to think so, but I don't, not really... there is a lot of
information out there that seems to indicate it's a real danger.

Rick WA1RKT


The problem with relying on the rig's metal case for shielding is that it's
not the metal thickness, so much as the gaps in the metal, that kill the
shielding effectiveness. Any reasonable metal (steel, aluminum, copper) in
any thickness reasonably needed to act as a chassis and cabinet, will give
you tremendous shielding effectiveness. Unfortunately, once you have welded
your rig into a steel tank, it's a bit hard to use.

The joints on a commercial rig only need to hold the pieces together if you
vigorously shake the box. You can only achieve decent shielding if you
carefully bond every joint, gasket every flange, design every cover and
access panel with an RF gasket and control every interface port (including
meter faces, air vents, handles, control shafts, plastic bezels and display
panels).

If you ever tried to harden a commercial rig, you will come up against so
many shielding violations that you will usually be better off to move the
protection perimeter out from the rig case, and build a shielded workstation
or enclosure.

Ed
WB6WSN