On Wed, 21 Nov 2007 11:58:03 -0600, Ignoramus4770
wrote:

On 2007-11-21, Leon Fisk wrote:
On Tue, 20 Nov 2007 15:12:19 -0600, Ignoramus10223
wrote:

I would be amazed if simple "wrap it in foil and use twisted wire"
approach did not 100% prevent premature detonation through any kind of
RF generator.

i

I worked in two-way radio/RF for most of my career. It
really isn't all that easy to shield things from RF. What
looks good to the eye can leak horribly and what you would
swear could never work does...


But would RF deliver enough amps to cause detonation?

i

IF you got lucky and hit a resonate frequency, maybe, but I
really doubt if this is useable. Remember these guys have
their own communication equipment that can't be knocked
off-line for any length of time either. If you make
something powerful enough to detonate the IED's they will
most likely wipe out their own communications. I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Most of out local commercial broadcast radio and TV stations
are pumping out at least 50,000 watts, some more. Do these
seem to have any noticeable effect on stuff that you've
seen? Think about how much power it would take to do
something like what you are considering when a 50,000 watt
station does bother things all that much.

If I was going to try and make something it would look like
a four wheel dumpster that you push down the road ahead of
the vehicle. An angled heavy blast plate towards the vehicle
to deflect blasts up/over and wheels that track the same as
the vehicles. It should be heavy enough to trip the IED
pressure plate. A quick disconnect hook-up so it could
quickly released and jettisoned from the inside of the
vehicle (shrug). KISS

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Wed, 21 Nov 2007 15:10:43 -0500, Leon Fisk
wrote:

On Wed, 21 Nov 2007 11:58:03 -0600, Ignoramus4770
wrote:

On 2007-11-21, Leon Fisk wrote:
On Tue, 20 Nov 2007 15:12:19 -0600, Ignoramus10223
wrote:

I would be amazed if simple "wrap it in foil and use twisted wire"
approach did not 100% prevent premature detonation through any kind of
RF generator.

i

I worked in two-way radio/RF for most of my career. It
really isn't all that easy to shield things from RF. What
looks good to the eye can leak horribly and what you would
swear could never work does...


But would RF deliver enough amps to cause detonation?

i

IF you got lucky and hit a resonate frequency, maybe, but I
really doubt if this is useable. Remember these guys have
their own communication equipment that can't be knocked
off-line for any length of time either. If you make
something powerful enough to detonate the IED's they will
most likely wipe out their own communications. I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Why do you think it would take so much power? How much power do you
think it takes to initiate an electric cap?

Hint: U.S. military caps are specified to initiate with 16.3
millijoules of energy delivered in a period of not less than 10
milliseconds nor more than 24 milliseconds. That's a power level of
between 0.67 and 1.63 watts.

This isn't to say that the notions of flails and heavy blast-proof
non-manned vehicles aren't viable or even possibly best approaches,
only to argue that while they seem to be obviously viable approaches
they are not obviously the only viable approaches.

nick hull wrote:

In article
,
wrote:


I have been wondering if there is any way to inductively couple enough
current to prematurely detonate these suckers. Maybe an R/C car with
a rotating coil sort of thing. My knowledge of electricity pretty
much ends with "Don't stick coathangers into the wall socket". I know
that high-tension lines will sometimes induce power in fences running
parallel to the lines. Could this effect be useful against pressure
plate IEDs at a range of a foot or so? If any one has any thoughts on
the subject, no matter how bizarre, I'd love to hear 'em. (Other than
"Just Leave." While effective, it's not in the cards.)


Time tested method is to herd sheep over the area. The Russians used
troops that lacked dicipline.

May be they did, may be they did not. But what they would definitely
say - "get the hell out of this country, it's not yours".

C.

On Wed, 21 Nov 2007 17:09:08 -0600, Don Foreman
wrote:

On Wed, 21 Nov 2007 15:10:43 -0500, Leon Fisk
wrote:

On Wed, 21 Nov 2007 11:58:03 -0600, Ignoramus4770
wrote:

On 2007-11-21, Leon Fisk wrote:
On Tue, 20 Nov 2007 15:12:19 -0600, Ignoramus10223
wrote:

I would be amazed if simple "wrap it in foil and use twisted wire"
approach did not 100% prevent premature detonation through any kind of
RF generator.

i

I worked in two-way radio/RF for most of my career. It
really isn't all that easy to shield things from RF. What
looks good to the eye can leak horribly and what you would
swear could never work does...


But would RF deliver enough amps to cause detonation?

i

IF you got lucky and hit a resonate frequency, maybe, but I
really doubt if this is useable. Remember these guys have
their own communication equipment that can't be knocked
off-line for any length of time either. If you make
something powerful enough to detonate the IED's they will
most likely wipe out their own communications. I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Why do you think it would take so much power? How much power do you
think it takes to initiate an electric cap?

Hint: U.S. military caps are specified to initiate with 16.3
millijoules of energy delivered in a period of not less than 10
milliseconds nor more than 24 milliseconds. That's a power level of
between 0.67 and 1.63 watts.

This isn't to say that the notions of flails and heavy blast-proof
non-manned vehicles aren't viable or even possibly best approaches,
only to argue that while they seem to be obviously viable approaches
they are not obviously the only viable approaches.

I don't know much about blasting caps Don, but if it was as
easy as you say they would be going off all over the place
prematurely. Fire up an RF spectrum analyzer and take a look
around (preaching to the choir here , the airwaves are
filthy nowadays. A key tower site probably has 2 to 3+
50,000 watt transmitters, plus numerous (25-100) other
transmitters. The RF fields around these sites is pretty
impressive. Most of the people that used radios that I
serviced never bothered to read the warning tags that were
attached to the microphone.

I have read/know about the warning about using two-way radio
equipment in "blasting zones", but have never heard any
accounts of it touching off explosives. Have you heard/know
of any reputable examples of this happening? I get a lot of
Google hits on this and read some of the more promising
ones, but the radio involved wasn't to blame in the ones I
chose. I'm sure it has happened, otherwise there would be
dire warnings concerning this.

I've heard a lot of interesting tales through the years and
seen some stuff myself concerning radio. I'm not saying it
can't be done, but I think it would take a lot of power and
some luck. It would also probably wipe out/interfere with
their own communications too. Crap, just the onboard vehicle
computers used to wipe out a radios receiver at times.

I wonder if they still use blasting caps like you described
today. The use of radio type equipment has skyrocketed in
the Armed Forces. I would be concerned about them setting
off their own stuff prematurely.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Thu, 22 Nov 2007 14:24:15 -0500, Leon Fisk
wrote:

I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Why do you think it would take so much power? How much power do you
think it takes to initiate an electric cap?

Hint: U.S. military caps are specified to initiate with 16.3
millijoules of energy delivered in a period of not less than 10
milliseconds nor more than 24 milliseconds. That's a power level of
between 0.67 and 1.63 watts.

This isn't to say that the notions of flails and heavy blast-proof
non-manned vehicles aren't viable or even possibly best approaches,
only to argue that while they seem to be obviously viable approaches
they are not obviously the only viable approaches.

I don't know much about blasting caps Don, but if it was as
easy as you say they would be going off all over the place
prematurely.

Wires to caps are usually twisted. It's pretty hard to couple much RF
into twisted pair. They're kept shorted at the user end until just
before detonation.

In an IED, the wires must spread enough to at least accomodate a
battery. That isn't much, but very short wavelength could do it, like
10 to 20 GHz. Very directional antennae of managable size are
possible (and usual) at those wavelengths.


I wonder if they still use blasting caps like you described
today. The use of radio type equipment has skyrocketed in
the Armed Forces. I would be concerned about them setting
off their own stuff prematurely.

Yup. I took those numbers from a 2005 spec.

On Thu, 22 Nov 2007 14:09:38 -0600, Don Foreman
wrote:

On Thu, 22 Nov 2007 14:24:15 -0500, Leon Fisk
wrote:

I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Why do you think it would take so much power? How much power do you
think it takes to initiate an electric cap?

Hint: U.S. military caps are specified to initiate with 16.3
millijoules of energy delivered in a period of not less than 10
milliseconds nor more than 24 milliseconds. That's a power level of
between 0.67 and 1.63 watts.

This isn't to say that the notions of flails and heavy blast-proof
non-manned vehicles aren't viable or even possibly best approaches,
only to argue that while they seem to be obviously viable approaches
they are not obviously the only viable approaches.

I don't know much about blasting caps Don, but if it was as
easy as you say they would be going off all over the place
prematurely.

Wires to caps are usually twisted. It's pretty hard to couple much RF
into twisted pair. They're kept shorted at the user end until just
before detonation.

In an IED, the wires must spread enough to at least accomodate a
battery. That isn't much, but very short wavelength could do it, like
10 to 20 GHz. Very directional antennae of managable size are
possible (and usual) at those wavelengths.


I wonder if they still use blasting caps like you described
today. The use of radio type equipment has skyrocketed in
the Armed Forces. I would be concerned about them setting
off their own stuff prematurely.

Yup. I took those numbers from a 2005 spec.

The biggest problem I see with trying to do this is jamming
up your own equipment, causing either radio or vehicle
malfunction. How long do you think it will take for the
creator to use this to their advantage, ie plant the IED
knowing fully well that the Military will help detonate it
for you with a transmitting device.

Trying to create a tool to work against a morphing target
won't be simple, if not impossible. I would be curious to
know too if the majority of the IED's even use a blasting
cap or some other sort of detonator. Are they buried in a
dirt road, paved, culvert? Not knowing some of these
questions makes it even harder to suggest remedies.

I can think of lots of ways to defeat what we are trying to
create, I suspect the bad guys can too (shrug).

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

"Leon Fisk" wrote in message
...
On Thu, 22 Nov 2007 14:09:38 -0600, Don Foreman
wrote:

On Thu, 22 Nov 2007 14:24:15 -0500, Leon Fisk
wrote:

I wouldn't be
surprised if on-board computers in vehicles went berserk and
shut down too at the levels it would most likely take.

Why do you think it would take so much power? How much power do you
think it takes to initiate an electric cap?

Hint: U.S. military caps are specified to initiate with 16.3
millijoules of energy delivered in a period of not less than 10
milliseconds nor more than 24 milliseconds. That's a power level of
between 0.67 and 1.63 watts.

This isn't to say that the notions of flails and heavy blast-proof
non-manned vehicles aren't viable or even possibly best approaches,
only to argue that while they seem to be obviously viable approaches
they are not obviously the only viable approaches.

I don't know much about blasting caps Don, but if it was as
easy as you say they would be going off all over the place
prematurely.

Wires to caps are usually twisted. It's pretty hard to couple much RF
into twisted pair. They're kept shorted at the user end until just
before detonation.

In an IED, the wires must spread enough to at least accomodate a
battery. That isn't much, but very short wavelength could do it, like
10 to 20 GHz. Very directional antennae of managable size are
possible (and usual) at those wavelengths.


I wonder if they still use blasting caps like you described
today. The use of radio type equipment has skyrocketed in
the Armed Forces. I would be concerned about them setting
off their own stuff prematurely.

Yup. I took those numbers from a 2005 spec.

The biggest problem I see with trying to do this is jamming
up your own equipment, causing either radio or vehicle
malfunction. How long do you think it will take for the
creator to use this to their advantage, ie plant the IED
knowing fully well that the Military will help detonate it
for you with a transmitting device.

Trying to create a tool to work against a morphing target
won't be simple, if not impossible. I would be curious to
know too if the majority of the IED's even use a blasting
cap or some other sort of detonator. Are they buried in a
dirt road, paved, culvert? Not knowing some of these
questions makes it even harder to suggest remedies.

I can think of lots of ways to defeat what we are trying to
create, I suspect the bad guys can too (shrug).

Excuse me for jumping in at this late date, but what are you guys trying to
do, transmit a lot of radio-wave energy to IEDs? If so, you're going to have
to get 'way up into the microwave region to transmit any significant energy,
right? E=hf or E=hv, where h is Planck's constant and all that.

If I'm missing the point, then never mind. d8-)

--
Ed Huntress

Ed Huntress wrote:
"Leon Fisk" wrote in message
...
(...)

I can think of lots of ways to defeat what we are trying to
create, I suspect the bad guys can too (shrug).


Excuse me for jumping in at this late date, but what are you guys trying to
do, transmit a lot of radio-wave energy to IEDs? If so, you're going to have
to get 'way up into the microwave region to transmit any significant energy,
right? E=hf or E=hv, where h is Planck's constant and all that.

If I'm missing the point, then never mind. d8-)

You got it Ed.

I figure a 200 W microwave amplifier should result in ca 100 KW ERP at
the feed horn of a 30" diameter parabolic dish. After allowing for
space attenuation and shielding, would it reduce the IED to carbon
quickly enough to make it safe?

--Winston

"Winston" wrote in message
news:41m1j.25967$9h.16202@trnddc07...
Ed Huntress wrote:
"Leon Fisk" wrote in message
...
(...)

I can think of lots of ways to defeat what we are trying to
create, I suspect the bad guys can too (shrug).


Excuse me for jumping in at this late date, but what are you guys trying
to do, transmit a lot of radio-wave energy to IEDs? If so, you're going
to have to get 'way up into the microwave region to transmit any
significant energy, right? E=hf or E=hv, where h is Planck's constant and
all that.

If I'm missing the point, then never mind. d8-)

You got it Ed.

I figure a 200 W microwave amplifier should result in ca 100 KW ERP at the
feed horn of a 30" diameter parabolic dish. After allowing for space
attenuation and shielding, would it reduce the IED to carbon quickly
enough to make it safe?

Practical microwaves are not my department; I only have brushed with
theoretical stuff, from long ago when I was studying for a radar
endorsement.

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

I guess the needs here fall somewhere in between. d8-) There's a lot of
comment that's been published on microwave weapons, so it should be
researchable.

--
Ed Huntress

Ed Huntress wrote:

(...)

I guess the needs here fall somewhere in between. d8-) There's a lot of
comment that's been published on microwave weapons, so it should be
researchable.

--
Ed Huntress

Thanks Ed.

I am sure there is enough microwave talent on this NG to produce a
reasonable guess as to practicability, frequency and power level.

--Winston

Winston wrote:

I figure a 200 W microwave amplifier should result in ca 100 KW ERP at
the feed horn of a 30" diameter parabolic dish.

You may be confusing ERP and presumably ERIP (power relative to that
radiated by a dipole or an isotropic radiator respectively) with raw
power. ERP is the amount of power you would have to feed to a dipole to
get the same energy that the directional antenna delivers to a given
area. A high gain antenna does not generate power; it puts a given
amount of power into a smaller area. If you need 200 Watts of power
coupled into something for some purpose, you will need to feed the
antenna with a lot more than 200 Watts.


Kevin Gallimore

axolotl wrote:

Winston wrote:

I figure a 200 W microwave amplifier should result in ca 100 KW ERP at
the feed horn of a 30" diameter parabolic dish.


You may be confusing ERP and presumably ERIP (power relative to that
radiated by a dipole or an isotropic radiator respectively) with raw
power. ERP is the amount of power you would have to feed to a dipole to
get the same energy that the directional antenna delivers to a given
area.

Yes, if you couple 200 W into a ~30 dbi parabolic antenna, it will
radiate as much power (into a spot) as would a dipole driven by ~100 KW
(into the same area, though the dipole is radiating isotropically).

(Power != field strength, always.)

A high gain antenna does not generate power; it puts a given
amount of power into a smaller area.

Yes. Just the ticket for inducing eddy current and the resulting power
dissipation in conductors within a limited, steerable aperture.

If you need 200 Watts of power
coupled into something for some purpose, you will need to feed the
antenna with a lot more than 200 Watts.

Yes. But the necessary power into the load (sans resonance) could be as
little as say 2 W given Don's range of 0.67 W to 1.63 W. My question
is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the initiator,
would that reliably disarm or failing that, trigger the device?

--Winston

In article ,
"Ed Huntress" wrote:

"Winston" wrote in message
news:41m1j.25967$9h.16202@trnddc07...
Ed Huntress wrote:
"Leon Fisk" wrote in message
...
(...)

I can think of lots of ways to defeat what we are trying to
create, I suspect the bad guys can too (shrug).


Excuse me for jumping in at this late date, but what are you guys trying
to do, transmit a lot of radio-wave energy to IEDs? If so, you're going
to have to get 'way up into the microwave region to transmit any
significant energy, right? E=hf or E=hv, where h is Planck's constant and
all that.

If I'm missing the point, then never mind. d8-)

You got it Ed.

I figure a 200 W microwave amplifier should result in ca 100 KW ERP at the
feed horn of a 30" diameter parabolic dish. After allowing for space
attenuation and shielding, would it reduce the IED to carbon quickly
enough to make it safe?

Practical microwaves are not my department; I only have brushed with
theoretical stuff, from long ago when I was studying for a radar
endorsement.

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

I guess the needs here fall somewhere in between. d8-) There's a lot of
comment that's been published on microwave weapons, so it should be
researchable.

The problem is more fundamental. While high-power microwaves (HPMs) can
and have set ordinance off, it's very random as it depends on accidental
resonances and shielding flaws and is in any event quite inefficient.
Safety regulations are designed to make a low rate essentially zero, to
cut down on fratricide. However, the natural low rate is really too low
to be militarily effective.

Nor is the enemy stupid - if we start neutralizing too many IEDs with
HPM, pretty soon IEDs will have improved shielding. Shielding is far
cheaper than deployment of sufficient HPM gear, making the economic
tradeoff unattractive. Some other way will be found.

Joe Gwinn

On Thu, 22 Nov 2007 16:21:20 -0500, "Ed Huntress"
wrote:

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

Funny you should mention this. I just read an article in the
paper last night about this, gives me the creeps. They have
some portable units now (if you call a Humvee portable) and
are just itching to deploy them in Iraq. See:

http://www.telegraph.co.uk/news/main...wdenial118.xml

http://www.telegraph.co.uk/news/main...wdenial218.xml

There are plenty more articles around if you care to search.

I don't think that it will produce the results that they are
hoping for...

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

"Leon Fisk" wrote in message
...
On Thu, 22 Nov 2007 16:21:20 -0500, "Ed Huntress"
wrote:

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable
degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

Funny you should mention this. I just read an article in the
paper last night about this, gives me the creeps. They have
some portable units now (if you call a Humvee portable) and
are just itching to deploy them in Iraq. See:

http://www.telegraph.co.uk/news/main...wdenial118.xml

http://www.telegraph.co.uk/news/main...wdenial218.xml

There are plenty more articles around if you care to search.

I don't think that it will produce the results that they are
hoping for...

But they could soup them up a little bit and they'd have a novel way to cook
a turkey. d8-)

--
Ed Huntress

On Fri, 23 Nov 2007 13:58:30 -0500, "Ed Huntress"
wrote:


"Leon Fisk" wrote in message
.. .
On Thu, 22 Nov 2007 16:21:20 -0500, "Ed Huntress"
wrote:

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable
degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

Funny you should mention this. I just read an article in the
paper last night about this, gives me the creeps. They have
some portable units now (if you call a Humvee portable) and
are just itching to deploy them in Iraq. See:

http://www.telegraph.co.uk/news/main...wdenial118.xml

http://www.telegraph.co.uk/news/main...wdenial218.xml

There are plenty more articles around if you care to search.

I don't think that it will produce the results that they are
hoping for...

But they could soup them up a little bit and they'd have a novel way to cook
a turkey. d8-)

I'm already wondering if another parabolic dish could
reflect this right back at them or other "good guys". Also
what type of surface or objects may do the same. Interesting
to ponder and I'm sure others are thinking along the same
lines.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Winston wrote:

My question
is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the initiator,
would that reliably disarm or failing that, trigger the device?


I don't know. The MIL-STD for EEDs is MIL-STD-1576. The "safe current"
(the max current/power/time for the squib not firing) listed in the spec
is 1A/1W/5min. Do the bad guys use parts made to the same spec? Do you
want to have to get within 24" for it to work?

A Friis equation calculator is available he

http://www.learningmeasure.com/cgi-b...ators/friis.pl

When you start playing with power/frequency/and antenna gain, it backs
you into path loss and radiator size.

You will have a polarization mismatch (circular (presumably) to
something random), and what is probably a lousy match between squib and
antenna.

It would be interesting to experiment, and the task is a worthy one.

You could measure the result of your effort the way EEDs are checked on
aircraft. An optical fiber coated with temperature dependent phosphor is
brought into contact with the squib active element. The other end of the
fiber is coupled to a flashtube and a sensor. The phosphor is flashed
and the decay time of the phosphor is measured. the decay time is
proportional to temperature. You hit the aircraft with 200V/meter and
check the squib for a temperature rise.


Kevin Gallimore

Leon Fisk wrote:

On Thu, 22 Nov 2007 16:21:20 -0500, "Ed Huntress"
wrote:

You may want to look at the millimeter-wave (95 GHz) Active Denial system,
V-MADS, to see if it provides any clues. They don't seem to transmit much
power, just enough to heat up the target (human) to an uncomfortable degree.
And the systems tested for missile defense run around 4 trillion Watts: a
12-16 million Amp pulse with a rise time of 400 nanoseconds. These are
powered by big flux compressors.

Funny you should mention this. I just read an article in the
paper last night about this, gives me the creeps. They have
some portable units now (if you call a Humvee portable) and
are just itching to deploy them in Iraq. See:

http://www.telegraph.co.uk/news/main...wdenial118.xml

http://www.telegraph.co.uk/news/main...wdenial218.xml

There are plenty more articles around if you care to search.

I don't think that it will produce the results that they are
hoping for...

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

all you need to have is a tin foil beanie for protection and a satalite
dish to redirect the beam back to the source.

Its the same crap as shooting down missles with lasers. All the
protection needed is to coat the missle with a flashed copper film which
is over 90 % reflective to a co2 laser.

John

axolotl wrote:

Winston wrote:

My question

is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the
initiator, would that reliably disarm or failing that, trigger the
device?



I don't know. The MIL-STD for EEDs is MIL-STD-1576. The "safe current"
(the max current/power/time for the squib not firing) listed in the spec
is 1A/1W/5min. Do the bad guys use parts made to the same spec? Do you
want to have to get within 24" for it to work?

I googled and found a 1 KW amplifier good for 30 W at 24". Kewl.


A Friis equation calculator is available he

http://www.learningmeasure.com/cgi-b...ators/friis.pl

Bookmarked. Thanks!

When you start playing with power/frequency/and antenna gain, it backs
you into path loss and radiator size.

You will have a polarization mismatch (circular (presumably) to
something random), and what is probably a lousy match between squib and
antenna.

It would be interesting to experiment, and the task is a worthy one.

You could measure the result of your effort the way EEDs are checked on
aircraft. An optical fiber coated with temperature dependent phosphor is
brought into contact with the squib active element. The other end of the
fiber is coupled to a flashtube and a sensor. The phosphor is flashed
and the decay time of the phosphor is measured. the decay time is
proportional to temperature. You hit the aircraft with 200V/meter and
check the squib for a temperature rise.

Very clever!

--Winston

On Fri, 23 Nov 2007 19:33:01 -0500, axolotl
wrote:

Winston wrote:

My question
is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the initiator,
would that reliably disarm or failing that, trigger the device?


I don't know. The MIL-STD for EEDs is MIL-STD-1576. The "safe current"
(the max current/power/time for the squib not firing) listed in the spec
is 1A/1W/5min. Do the bad guys use parts made to the same spec? Do you
want to have to get within 24" for it to work?

A Friis equation calculator is available he

http://www.learningmeasure.com/cgi-b...ators/friis.pl

When you start playing with power/frequency/and antenna gain, it backs
you into path loss and radiator size.

You will have a polarization mismatch (circular (presumably) to
something random), and what is probably a lousy match between squib and
antenna.

It would be interesting to experiment, and the task is a worthy one.

You could measure the result of your effort the way EEDs are checked on
aircraft. An optical fiber coated with temperature dependent phosphor is
brought into contact with the squib active element. The other end of the
fiber is coupled to a flashtube and a sensor. The phosphor is flashed
and the decay time of the phosphor is measured. the decay time is
proportional to temperature. You hit the aircraft with 200V/meter and
check the squib for a temperature rise.


Kevin Gallimore

200 V/meter is only about 106 W/m^2. That'd be a pretty good radar
smack on an airframe so it's certainly a reasonable level for the test
you describe ... but it isn't necessarily telling here.

The Friis equation and other path loss calculations assume far field,
not the case here.

The squib will be a good match to its antenna at some frequency,
because Zo of a dipole depends on length /wavelength.

An xmit antenna or feed working against a reflector of about 1 sq
meter will have a footprint not much larger than that at distance
comparable to reflector dimensions, so if the xmtr is 1KW then
there'll be power density of about 1 KW/m^2 beneath it. This need
not be a parabolic reflector, could be a planar array. If the squib
+ lead separation is ca. 60 mm (length of a flashlight battery), then
aperture might be ca. 3.6E-03 m^2, capturing 3.6 watts per kilowatt.
3.6 watts is more than ample to fire a cap.

Again, I don't assert that this is the best or even a viable
approach, but only a politician, bureaucrat or seat-of-pants "expert"
could dismiss it out of hand with arguments presented thus far.
Shielding would certainly be an issue, though achieving effective
shielding is not nearly as easy as it has been made out to be by most
here.

I agree that some experiments would be interesting and that some
investigation is merited. It's probably most likely to happen by
motivated and skilled people on the ground working with a scrounged
radar, a bit of expertise and more than a bit of creativity.

On Sat, 24 Nov 2007 00:40:16 -0600, Don Foreman
wrote:

On Fri, 23 Nov 2007 19:33:01 -0500, axolotl
wrote:

Winston wrote:

My question
is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the initiator,
would that reliably disarm or failing that, trigger the device?

By the way, a 1.2 KW 2.2 GHz transmitter is not at all difficult to
come by, maybe 60 bux. Look in the microwave oven department at
Wal-Mart. A half wavelength at 2.2 GHz is about 68 mm, close to the
length of a flashlight battery......

Don Foreman wrote:
On Sat, 24 Nov 2007 00:40:16 -0600, Don Foreman
wrote:


On Fri, 23 Nov 2007 19:33:01 -0500, axolotl
wrote:


Winston wrote:

My question

is: if we provide a 30" diameter field that has a power density of 2 W
at 24" and we are radiating at the resonant frequency of the initiator,
would that reliably disarm or failing that, trigger the device?


By the way, a 1.2 KW 2.2 GHz transmitter is not at all difficult to
come by, maybe 60 bux. Look in the microwave oven department at
Wal-Mart. A half wavelength at 2.2 GHz is about 68 mm, close to the
length of a flashlight battery......

We've come full circle to Bill's magnetron gadget.
Old but functional microwave ovens are free for the asking in my
neighborhood.

--Winston