"Chuck Harris" wrote in message
...
The EMP problem is very well studied, and very classified. You
won't find much detailed information. The US has spent
billions of dollars studying it. The amount of money spent should
act as an indicator of the danger of the effect.

EMP is far worse than lightning! This is because the risetime of EMP
is in the sub pico second region. Even a dead short circuit looks
like an inductor at these frequencies.

Now, on the bright side, all of the IC manufacturers have been
hardening their ICs for electro static and EMP effects for at least
the last 20 years. They know the score, and don't want their stuff
fizzling with EMP. EMP hardened pads cost them nothing to include.

As to tube gear surviving EMP, every commercial tube rig made
in the '60s and 70s had some solidstate in it. The HW101 had a solid
state LTO, the HW100 was tube, with a varactor to shift the vFO for
usb/lsb. Same with the SB100/101. SB102 had a ss LTO. Diodes were
used here and there to aid in T/R switching....

If spamsink is really interested in having a rig that will survive EMP
he should look at some of the US military solid state gear. It is all
hardened. Or, on a cheaper note, put an ICOM in a copper can.

-Chuck, WA3UQV

One of the best RF shielded structures is available for a couple of dollars
at your local hardware store. Just buy a couple of 1 gallon steel paint
cans. Drop in your survival radio and a battery, and tap the top back on. (A
true survivalist would also can a good revolver and a couple of boxes of
ammo; not for NEMP protection, just for convenience.) The mechanical wiping
interference fit of the lid makes for an excellent RF shield. Watch out for
some cans with an internal plastic film; either get the metal plated cans,
or buff off the plastic film from the can and lid seal faces.

The scenario for NEMP is 50,000 volts per meter electric field strength at
the Earth's surface. If you want to protect your equipment from this threat,
then you have to treat every interface to your rig. That means shielding the
case and filtering / limiting the power cable, any computer I/O lines, any
external meters or speakers, and the antenna cable. The easiest way to do
all this is to put the rig, plus speakers and meters, into a very conductive
box (Faraday cage). Use a powerline filter with transient limiters to bring
power into the box. Use a fast-acting limiter (designed with NEMP in mind)
on the coax. Provide ventilation through honeycomb or multiple small
diameter holes.

By now, you may have noticed that although the rig is protected, you have
created a very difficult to use station. OK, just make your shielded box
bigger, and climb inside. A decent home-made shielded box should easily give
you 80 dB or so of shielding effectiveness, which is a 10,000x reduction,
thus exposing the rig to only 5 V/M of the 50,000 V/M NEMP.

Remember that you are only protected when the access door is properly
closed. It won't do any good if you do everything else correct, but leave
the door hanging open an inch.

Finally, a note about military gear. Not all mil equipment is procured to
the same performance level. Since shielding and other protection adds
weight, bulk and cost, some mil equipment is built tougher than other mil
equipment. An RF transponder used in a submarine has less need for NEMP
hardening (the sub hull and the water provide a lot of shielding) than a
composite airframe missile. OTOH, what are the odds of a missile being
in-flight during a nuclear event? (Harden the launcher box, not the vehicle
itself.) So, although any mil equipment is more likely to survive an NEMP
than civilian stuff, some mil stuff is a lot better than other mil stuff. If
you are buying surplus mil gear, consider the original mission scenario and
the threats to that mission.

Ed
WB6WSN