"BlackBeard" wrote in message
...
On Apr 8, 7:41 am, "William Black"
wrote:
"Juergen Nieveler" wrote in message

. ..



BTW, do those jammers send white noise, or are they smart enough to
fake a signal? Say, I build a small detonator from RC car parts, and it
depends on the transmitter sending "left, right, left..." every 30
seconds, with a timer starting on every signal, counting down until the
opposite side timer is started.

With a white noise jammer, no signal gets through anymore, 30 seconds
later you get *bang*...

All this stuff came out at the inquest into the people shot in Gib. The
claim was made that the security forces should be able to jam the signal.

They explained in some detail why they couldn't.

It seems that the IRA people used a Trio Radio Amateur 144 MHz pocket
radio
system that requires a sequence of reversals transmitted by VHF FSK to
trigger an open channel. The sequence is set by a row of five thumbwheels,
each of ten digits.

So you've got a million, minus one, possible combinations.

I leave as an exercise for the reader the calculation of the linear
recursive sequence necessary to trigger the thing prematurely...

This, of course, assumes the security forces know the radio frequency and
the FSK baud rate and frequency shift.

White noise generators don't work once the bad guys get up to 'radio
amateur' levels of knowledge of triggering technology...


Gibraltar was 20 years ago. They've learned a lot since then and
deaths from IED's have dropped dramatically since the USN's EW experts
have trained the soldiers to use the equipment correctly.

"They called themselves "sand sailors," and they did their job well by
reducing IED fatalities at their bases. Monthly U.S. troop deaths from
IEDs have dropped since reaching a high of 90 in May to 17 last month,
in part because of their efforts, the military said in awarding Bronze
Stars to Dye and others."

----------------------------

Almost certainly the big drop was caused by training people how to spot the
bloody things.

Messing with the trigger mechanism is very much a secondary thing, the best
solution is not to park next door to one...

--
William Black


I've seen things you people wouldn't believe.
Barbeques on fire by the chalets past the castle headland
I watched the gift shops glitter in the darkness off the Newborough gate
All these moments will be lost in time, like icecream on the beach
Time for tea.