Mike Luther wrote:
A friend of mine cited a claim in a brand new book, "The Lost Symbol" by
Dan Brown. So said, in it is a claim of a new weapon of choice that is
installed in some USA military helicopters which is cable of aiming an
actual EMP pulse at a target below that destroys computer and electronic
equipment of focus to the pulse! Same as a 'normal' 30Megavolt/Meter
EMP pulse from a nuclear device, or even a huge Solar Burst. As told me
they used it recently to silence an Email production site they had to
quickly do so that they couldn't do any other way, per this book....

Duhh .....

Few people seem to recall the last huge Solar Burst we got here in the
USA in the mid-1800's about the time of the Golden Spike. So history
says, it completely took out most of all the at-the-time telegraph
systems which all had to be rebuilt or replaced.

At any rate, can anyone here conjecture, or better still, teach me how
it would be possible to create and focus an EMP pulse that could be used
as described in an airborne delivery machine? What might the antenna be
like?

Just curious.

W5WQN


Gyrotron, driven by a Flux Compression Generator.

basically a very high power microwave transmitting tube at a high enough
frequency where a moderate sized antenna gives a narrow beamwidth (e.g.
at 10GHz, a 2 meter antenna has about a 1 degree beamwidth.. 100GHz with
a 20 cm antenna does the same.) , with a HV pulse generator that uses
the mechanical energy from an explosion to generate the HV high current
pulse to run the tube.


Now.. 30 MV/m at a distance of say, 200 meters..

Assuming you're in the far field, so E/H = 377 ohms.. H = 30MV/m/ 377 =
0.08 MA/m. 30MV/m * 80kA/m = 2.4E12 W/m^2... that's a pretty high power
density (far higher than you'd need, in this application by the way...
a few tens of kW/square meter would probably do)

But, continuing on.. let's say you've got a 0.57 degree beamwidth.
That's about 0.01 radian, so at 200m, the "spot" is 2 meters in
diameter, or, call it 3-4 square meters.

That means the source has to put out a peak power of about 1E13 Watts..
Say the pulse is a microsecond long.. that's 1E7 joules (10 Megajoules)
which isn't a lot of energy. But a terawatt peak power? That's hard to
believe.

So lets move on.. Average powers of a megawatt are certainly
reasonable.. Let's scale back our field to 30 kV/m (so the power density
is now 2.4E6W/m^2... still 2400 times brighter than the sun)

That's a lot more realistic, and still enough to zap stuff.

"Jim Lux" wrote in message
...
Mike Luther wrote:
A friend of mine cited a claim in a brand new book, "The Lost Symbol" by
Dan Brown. So said, in it is a claim of a new weapon of choice that is
installed in some USA military helicopters which is cable of aiming an
actual EMP pulse at a target below that destroys computer and electronic
equipment of focus to the pulse! Same as a 'normal' 30Megavolt/Meter EMP
pulse from a nuclear device, or even a huge Solar Burst. As told me they
used it recently to silence an Email production site they had to quickly
do so that they couldn't do any other way, per this book....

Duhh .....

Few people seem to recall the last huge Solar Burst we got here in the
USA in the mid-1800's about the time of the Golden Spike. So history
says, it completely took out most of all the at-the-time telegraph
systems which all had to be rebuilt or replaced.

At any rate, can anyone here conjecture, or better still, teach me how it
would be possible to create and focus an EMP pulse that could be used as
described in an airborne delivery machine? What might the antenna be
like?

Just curious.

W5WQN


Gyrotron, driven by a Flux Compression Generator.

basically a very high power microwave transmitting tube at a high enough
frequency where a moderate sized antenna gives a narrow beamwidth (e.g. at
10GHz, a 2 meter antenna has about a 1 degree beamwidth.. 100GHz with a 20
cm antenna does the same.) , with a HV pulse generator that uses the
mechanical energy from an explosion to generate the HV high current pulse
to run the tube.


Now.. 30 MV/m at a distance of say, 200 meters..

Assuming you're in the far field, so E/H = 377 ohms.. H = 30MV/m/ 377 =
0.08 MA/m. 30MV/m * 80kA/m = 2.4E12 W/m^2... that's a pretty high power
density (far higher than you'd need, in this application by the way... a
few tens of kW/square meter would probably do)

But, continuing on.. let's say you've got a 0.57 degree beamwidth. That's
about 0.01 radian, so at 200m, the "spot" is 2 meters in diameter, or,
call it 3-4 square meters.

That means the source has to put out a peak power of about 1E13 Watts..
Say the pulse is a microsecond long.. that's 1E7 joules (10 Megajoules)
which isn't a lot of energy. But a terawatt peak power? That's hard to
believe.

So lets move on.. Average powers of a megawatt are certainly reasonable..
Let's scale back our field to 30 kV/m (so the power density is now
2.4E6W/m^2... still 2400 times brighter than the sun)

That's a lot more realistic, and still enough to zap stuff.


.... but how much damage is a pulse of 10 GHz RF going to do? The
effectiveness of a nuclear EMP much to do with its very broad bandwidth (as
well as its rise time).

Not that I know anything about the subject, Officer.

Chris

On Tue, 6 Oct 2009 10:43:10 +0100, "christofire"
wrote:

... but how much damage is a pulse of 10 GHz RF going to do?

Stand in front of an unfocussed emitter such as an open microwave oven
for 10 minutes (say, a meter back); that would be about 100,000
pulses; divide your noted effects by the same number and report back.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 6 Oct 2009 10:43:10 +0100, "christofire"
wrote:

... but how much damage is a pulse of 10 GHz RF going to do?

Stand in front of an unfocussed emitter such as an open microwave oven
for 10 minutes (say, a meter back); that would be about 100,000
pulses; divide your noted effects by the same number and report back.

73's
Richard Clark, KB7QHC


If you believe that's the basis of EMP then I won't argue with your opinion.

Chris

On Wed, 7 Oct 2009 00:26:44 +0100, "christofire"
wrote:

If you believe that's the basis of EMP then I won't argue with your opinion.

Hi Chris,

Your statement implies that a "basis" can lead to some new unique RF
phenomenon.

If EMP is co-opted for some trendy single purpose definition that
denudes the former understanding of its general (and still no less
applicable) meaning, then, yes, we have descended into opinionated
belief systems which depend upon faith.

What you infer by "basis" is that this particular pulse (with the
unstated nuclear detonation, or an e-bomb as the initiator) is somehow
different from all other pulses. No, not in the least. By whatever
"basis," there are very ordinary formulas that allow for rise time,
fall time, pulse duration, magnitude, and such artifacts as ringing
(undershoot, overshoot, crest, and the rest).

"Basis" is not another engineering term for magnitude. What was
astonishing through nuclear detonation was corralled and managed into
an e-bomb, which is nothing more remarkable than clever engineering of
shorting a capacitor. Each of the three could be cleverly induced to
give the same RF signature - what price "basis?" It happens a
trillion times a day with all the microwaves ovens on this earth.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 7 Oct 2009 00:26:44 +0100, "christofire"
wrote:

If you believe that's the basis of EMP then I won't argue with your
opinion.

Hi Chris,

Your statement implies that a "basis" can lead to some new unique RF
phenomenon.

If EMP is co-opted for some trendy single purpose definition that
denudes the former understanding of its general (and still no less
applicable) meaning, then, yes, we have descended into opinionated
belief systems which depend upon faith.

What you infer by "basis" is that this particular pulse (with the
unstated nuclear detonation, or an e-bomb as the initiator) is somehow
different from all other pulses. No, not in the least. By whatever
"basis," there are very ordinary formulas that allow for rise time,
fall time, pulse duration, magnitude, and such artifacts as ringing
(undershoot, overshoot, crest, and the rest).

"Basis" is not another engineering term for magnitude. What was
astonishing through nuclear detonation was corralled and managed into
an e-bomb, which is nothing more remarkable than clever engineering of
shorting a capacitor. Each of the three could be cleverly induced to
give the same RF signature - what price "basis?" It happens a
trillion times a day with all the microwaves ovens on this earth.

73's
Richard Clark, KB7QHC


The effects on equipment of repetitive cycles of incident electric field
strength with alternating polarity, constant period and equal rise and fall
times (AKA a sine wave), whether continuous or 'pulsed', are different from
the effects of an incident pulse of electric field strength with a short
rise time that is not broken up into harmonic cycles. The latter can induce
a high voltage pulse that is wideband in the same manner as the result of a
lightning strike, and this can propagate through an installation causing
damage. The former cannot do that. Of course, I appreciate the difference
is the spectral width of the incident 'signal'.

The example you gave was of the former type, radiation from a microwave
oven, whereas I had written about the latter type. An open microwave oven
may well cook a human but it won't have much effect on a power cable feeding
a computer other than, perhaps, melting the insulation! A wideband pulse of
electric field of sufficicient strength will damage the computer. But,
evidently, you disagree ...

Chris

On Wed, 7 Oct 2009 02:13:52 +0100, "christofire"
wrote:

The effects on equipment of repetitive cycles of incident electric field
strength with alternating polarity, constant period and equal rise and fall
times (AKA a sine wave), whether continuous or 'pulsed', are different from
the effects of an incident pulse of electric field strength with a short
rise time that is not broken up into harmonic cycles. The latter can induce
a high voltage pulse that is wideband in the same manner as the result of a
lightning strike, and this can propagate through an installation causing
damage. The former cannot do that. Of course, I appreciate the difference
is the spectral width of the incident 'signal'.

Hi Chris,

You are mixing frequency domain with time domain descriptions. Example
repeated from above:
a short rise time that is not broken up into harmonic cycles.

"A short rise time" is made up of an increasingly dense spectrum of
harmonic cycles. It cannot be otherwise.


The example you gave was of the former type, radiation from a microwave
oven, whereas I had written about the latter type.

You are now mixing modulation into the time domain to argue against a
frequency domain solution. Modulation, if anything, adds even more
spectral (harmonic cycle) products.

Besides, I offered you simply reduce the number of modulation cycles,
by their count, to reduce the effect to that of one cycle (of
modulation). A pulse is a modulation of one cycle (however poorly
shaped it may be, and it envelopes a pluarity of SHF cycles).

An open microwave oven
may well cook a human but it won't have much effect on a power cable feeding
a computer other than, perhaps, melting the insulation! A wideband pulse of
electric field of sufficicient strength will damage the computer. But,
evidently, you disagree ...

No, not evident at all. Any "effect" is more a function of amplitude
than a failure to warm insulation:
On Tue, 6 Oct 2009 10:43:10 +0100, "christofire"
wrote:
but how much damage is a pulse of 10 GHz RF going to do?
"How much damage" speaks specifically to that function of amplitude,
not pulse shape, not rise time, fall time, or the rest; and as you are
explicit in giving a specific frequency.... The microwave oven
example suitably answers this. A RADAR example does even better (and
still the results, save for amplitude, are the same).

73's
Richard Clark, KB7QHC

Richard Clark wrote:

"Basis" is not another engineering term for magnitude. What was
astonishing through nuclear detonation was corralled and managed into
an e-bomb, which is nothing more remarkable than clever engineering of
shorting a capacitor. Each of the three could be cleverly induced to
give the same RF signature - what price "basis?" It happens a
trillion times a day with all the microwaves ovens on this earth.

73's
Richard Clark, KB7QHC

Richard

To see you write that the "clever engineering of shorting a capacitor"
is remotely similar to standing in front of a microwave oven is very
disappointing to say the least. You are losing your edge.

You know very well that they aren't remotely similar in the effects
produced. For one thing the "clever engineering of shorting a
capacitor" is very misleading without at least some explanation of how
different it is from simply shorting a capacitor.

tom
K0TAR

On Tue, 06 Oct 2009 21:52:46 -0500, tom wrote:

To see you write that the "clever engineering of shorting a capacitor"
is remotely similar to standing in front of a microwave oven is very
disappointing to say the least. You are losing your edge.

You know very well that they aren't remotely similar in the effects
produced. For one thing the "clever engineering of shorting a
capacitor" is very misleading without at least some explanation of how
different it is from simply shorting a capacitor.

Hi Tom,

EMP is a fast charge/discharge event. EMP products come in three
flavors, I will only discuss the fastest. The fastest is rarely
described with a risetime less than 1nS, but I have seen others bandy
about the frequency of 10GHz, so we have to assume they have links to
literature that claim a risetime on the order of 33pS. Be that as it
may, mercury switches can switch a 1000V pulse into a 50Ohm load in
500ps. This is laboratory stuff, not armament. Armament can be
engineered to perform with larger supplies as one-shot disposable
switches (you don't run lab equipment to failure, new out of the box
on the first application of power). Such switches are controlled
access and limited sale items.

To generate this 10GHz pulse would require very, very short very, very
low resistance leads; which would, of course, become part of a tuned
(to 10GHz) circuit. The trigger device often employs a charge driven
shorting bar. It is only a matter of capacitance and low resistance
metalurgy from there.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Tue, 6 Oct 2009 10:43:10 +0100, "christofire"
wrote:

... but how much damage is a pulse of 10 GHz RF going to do?

Stand in front of an unfocussed emitter such as an open microwave oven
for 10 minutes (say, a meter back); that would be about 100,000
pulses; divide your noted effects by the same number and report back.

73's
Richard Clark, KB7QHC

More like, put your radio in a microwave and turn it on.

60 pulses/second (in the US).. 600W average power. Figure the power
density is probably in the 10 W/cm^2 rough order of magnitude, or
100kW/square meter. Peak to average ratio in a microwave oven is pretty
low (3?), so thermal effects on a lossy medium will be significant.


The 30kV/m (which is achievable as described earlier, a megawatt over
that 2 meter circular area) is around 24 times that. I think it's safe
to say that 30kV/m sorts of fields will fry stuff, in general, pretty
much independent of its resonant properties. Crumpled aluminum foil
sparks pretty well, as does steel wool.


As for personnel exposure..

Yep, you'll get a burn.. probably cook your eyeballs too. Although, at
100GHz, the penetration depth is small..Might just cook your skin off
like a horror movie.

I don't know what the penetration scale depth at 10 GHz is, off hand.
Certainly several cm (I'd expect it to scale as sqrt(1/f), and 2.45 GHz
in a microwave oven clearly penetrates 10 cm at least, or you couldn't
cook a big roast at all evenly)

That's the challenge, of course.. High enough fields to cause
arcs/breakdown to destroy the electronics, but low enough average power
that thermal effects are minimal, so you don't kill or injure the people.


1-10 MW peak powers at pulse lengths of microseconds are pretty standard
radar fare. Fire it at 1pps, and the average power will be down in the
few watts area, so personnel safety isn't as big a problem. There are
lots of cases of folks being exposed to fields of this magnitude
accidentally, and they don't die as a rule.

There is a tale in the FCC enforcement literature about a guy working on
a FM broadcast tower where he noticed sparking and smoke from his
protective garments after the station manager remotely turned the
transmitter on to full power.


On a smaller scale, I've accidentally killed quite a few pieces of
electronics with fast HV pulses. It kind of goes with the territory when
you fool with Marx banks and solid state electronics. Even fairly low
powered Tesla coils will do a number on garage door openers, but I think
that's because the GDOs are kind of cheap designs, with long wires
hanging out of them, and it doesn't take much to kill one. That's
basically discharging a 50pF cap charged to 100-200kV in a few tens of ns.