[mdlug] OT - IR jamming

[Aaron Kulkis]

Robert Meier wrote:
> Aaron,
> 
>> The statement that a device *MUST* accept interference did
>> not come about by forgetting to exclude it.
>> It's an act of commission...which means someone TOOK AN ACTION to include
>> that specification within federal law.
> 
> I disagree.
> 
> See 47 CFR 15.5, cited earlier in this thread.
> The "Class C warning stickers"  omit the "that may be caused by
> [authorized users of the frequency]".
> 
> Intended use of Part 15 radiators must yield to authorized
> users of the radio spectrum, just as off-road-vehicle drivers
> may not block public roads, and when intersecting a public road
> from off-road must yield right of way to the drivers on the road,
> but are not prohibitted from driving off-road (where otherwise allowed)
> nor prohibitted (where otherwise allowed) from driving on the public road.
> 

And "authorized users of the frequency" means people
specifically granted permission by the government to
use that frequency.

Numbers 1 and 2 in line to be "authorized users"
are government entities: military and police.

> 
> 
>> When I was in Baghdad, we had equipment which takes practical
>> advantage of these sorts of mandated weakness in electronic
>> devices (these same requirements are in place in practically
>> all countries where modern electronic devices are manufactured),
>> so the same thing applies to electronics in Iraq as what you
>> buy here in the States.
> 
> Much of the world has no recognized legal rights of the individual.
> Much less has right of free speech, free press, or peaceable assembly.
> I do not recognize the absence of such legal rights elsewhere as
> the vacation of those rights in the United States.
> Promoting rights of the individual and rule of law,
> opposing violent suppression of same,
> are among the reported reasons we are involved in Iraq.

And it's coming...slower than we wish, but quite fast
considering the society in question.
(it took the U.S. over 10 years to replace the Confederation
of the Revolutionary War with the present Federalist system).

> 
> 
> 
> The right of free speech, free press, the right
> to peaceably assemble, and their enforcement,
> the authority of the individual to listen, to observe,
> and to communicate (when not infringing the rights
> of others), has been demonstrated to be necessary to
> keep a "good" state from reacting to its fear,
> by becoming the tyranny that it would oppose.
> 
> IIRC, US civil servants (including the president)
> annually take an oath "to defend the Constitution
> of the United States against all enemies domestic
> and foreign".

And then practically every elected official then proceeds
to trample upon that oath :-(

> 
> 
> 
> Armed bank robbers are notorious for speeding and ignoring driving laws.
> A mandated kill-switch on automobiles is unlikely to
> stop armed bank robbers, but very likely to benefit carjackers.
> Murderers are not likely to observe "government-mandated
> weakness" in their IEDs.

It turns out is that off-the-shelf wireless systems which
are resistant to jamming are quite expensive compared to the
typical cell phone or FRS radio...by pushing up the cost of
the equipment, it has an impact on the numbers of devices
employed.

As it is, we're not finding the enemy is using jamming-resistant
radios (despite their availability)...they're opting for
cheap cell-phones and bottom-of-the-line Motorola FRS radios,
even though THEY DO KNOW that the equipment they are using
is getting jammed by our equipment.


> I hope our soldiers protection equipment does not depend
> on any assumed compliance of IEDs with laws of government,

Very little is assumed.
The "picture" (for lack of a better term) is composed of
whatever data is available.

Initially, most IEDs were detonated by command wire.

When allied forces started training to look for command
wire (or signs of command wire being concealed), the
opposing forces started switching to wireless devices
as the arming mechanism.

When our engineers developed a variety of jamming
systems, they opposition forces have switched away
from wireless control back to command wire and
passive devices hooked to timers.

Everything is changing...and the best picture is
provided by whatever EOD picks up after a detonation
(the thing about a bomb is...other than the explosives
themselves...the rest of the bomb's components,
particularly the control mechanisms, are still all
around (although usually singed and twisted/crumpled),
and readily identified when collected up and spread
out on a table.

> as I fear this would put our soldiers unnecessarily in harms way.
> I hope our soldiers protection equipment does depend,
> in this matter, on the laws of physics (mandated by God, not government)
> of electromagnetic radiation with which IEDs must comply,
> and compliance with which is not onerous to the honest citizen.

Right now, the worst thing out there is a device called
an EFP (explosively formed projectile).  It's an upgrade
of a successful assassination method -- the platter charge
attached to the bottom of a man-hole cover.

An EFP is a steel can, normally set in concrete...the can
is filled with explosive, with the detonator near the front,
and then covered with a shallow dish made of copper (concave
into the can.  When the explosive charge blows, the copper
blows-outwards while still maintaining a bond with the
rim of the steel can...as pressure builds, the copper
distends (easily because it is a ductile metal)...the
center of the now outward-bowing bowl is travelling
faster than the edges...once the edges release/tear from
the rim of the can, they snap inwards...forming a very
slender projectile, which by this time is moving at a
speed in the range of Mach 4 to Mach 6.

As you can imagine, this is extremely devastating to
anything it runs into -- even an M1 tank :-/

These devices are triggered by $15 off the shelf
motion-detectors like you would use to turn on
exterior security lighting, or to automatically
turn office lights when someone enters a room,
and turn them off some time after the room is empty.

There are some counter-measures for this device,
but the effectiveness is variable.



> 
> Concerned,