On Sun, 7 Sep 3903 14:51:24, wrote:


I think I mentioned elsewhere in these discussions that the main
reason I'm looking for an all-tube SSB/CW transceiver is for when (not
"if", unfortunately) terrorists manage to smuggle a nuclear weapon
into this country and set it off.

(Hell, no, I'm not paranoid, which one of my enemies told you that?)
:-(

No, you didn't mention it but most folk can read between the
lines.


I'm looking for something that has a reasonable chance of surviving
the resulting EMP, and that means tube gear.

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.


Now, someone else here said something about the KWM-2 having germanium
diodes in the balance modulator. Those aren't likely to survive any
meaningful EMP (they can't even survive a little heat from a soldering
iron, for Pete's sake) so that seems to let the KWM-2 out of the
running.

Of the other tube rigs mentioned ... Swan 260/270/350/500, Heath
SB100/101 and HW-100 (also HW-101?), Hallicrafters SR-150, NCX-5, etc.
.... how many of them have germanium diodes here and there that are
likely to get smoked? What other considerations are there that would
rule one of these other rigs in or out?

Rick WA1RKT

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.

Anyway, I'm guessing that the EMP risk is overstated. If my
radios can ride out an electrical storm a mile away, what is the
risk of a one nuke in the entire country?

At the 50 mile range, I'd guess that it would be just some static.
Anyone know how big a problem this is?



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

ckh wrote:
On Sun, 7 Sep 3903 14:51:24, wrote:


I think I mentioned elsewhere in these discussions that the main
reason I'm looking for an all-tube SSB/CW transceiver is for when (not
"if", unfortunately) terrorists manage to smuggle a nuclear weapon
into this country and set it off.

(Hell, no, I'm not paranoid, which one of my enemies told you that?)
:-(

"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

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

wrote in message
...
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