Hand Grenades

[surfrescue]

I've been told that certain radio frequencies can set off hand grenades. I don't know the specifics behind it, just that I'm supposed to clear my beach and call the fire marshall. My question is if digital or cellular phone frequencies can have the same effect and detonate a live grenade? Thanks.
I'm asking because I work as an ocean lifeguard and there have been instances where WWII era live grenades have been uncovered by people with metal detectors on the beach.

[bmf]

O.K. I'll try to answer your question and keep it fairly simple.
It is true that Electromagnetic Radiation (or EMR) can set off electrically initiated explosives. (basically things that require and electrical current to detonate). The key ID is usually some type of wiring. Cell phones and handheld radios could provide the necessary means of EMR to detonate an extremely sensitive electrically initiated device.
BUT- I can't think of any WWII grenades that used electrical fuzing. Even if there were any, the salty atmoshpere at the beach would seriously corrode any electrical components to the point that they would be electrically safe.
In short you are safe to use your radio around old world war 2 stuff. I would however always maintain about 10 ft of distance between your radio/cell and any unknown ordnance item. NOT picking it up is also a big suggestion. (that's what we get paid to do).
Also, if you call up the nearest Navy EOD team there is a chance they may be able to give your team a brief training session. (if they're not too busy)
Hope this answers your Q.
bmf

[surfrescue]

Yeah that helps. Thanks. The Ocean City Fire Marshall did a brief training seminar at our weekly meeting a few weeks ago and the question about the cell phones popped into my head after the meeting. Most of the ordinance we would deal with involve undetonated fireworks from 4th of July that wash up. We are told not to touch anything, clear the beach in a 100 yard radius and let the bomb technicians do the work. Tim

[colmurph]

Until I retired in 1993 ALL U.S. and Foreign Hand Grenades that were in current use were MECHANICALLY FIRED, that is with a firing pin that initiated a fuze train. None of them were elictrically fuzed. What this means is that you can operate a 15 Megawatt transmitter right next to it and it will not explode. Since your cell phone is probably putting out less than 50 watts I wouldn't worry about it.

[surfrescue]

Thanks for the responses. So far I've never had to deal with ordinance washing up, but you never know. I guess the fire marshall was just giving us general safety guidelines since none of us are EOD techs on the beach patrol. We were told to do all communications via landline if ordinance washed up or was uncovered by treasure hunters.

[colmurph]

The signs that you see around blasting sights "Do not transmit with a radio" are referring to electric blasting caps that can concievingly detonate if their wires have been unravelled to place the charge and the bridge is off the wires. During the short time that the wires are apart and not hooked to the main circuit they can act as an antenna and in theory at least, any strong signal with a wave length the same, 1/2 or 1/4 the length of the wires to the electric cap could set it off. Probably the only "Real" danger would be if a ham radio operator on the 10 meter band was transmitting while parked next to a blasting site.