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Author Topic: Solar 'death ray'...  (Read 4755 times)
KC8OYE
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Posts: 297




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« Reply #15 on: February 02, 2011, 11:15:31 PM »

The worst are gun myths, although they've gotten better.

These tracers are ILLEGAL! This gun is ILLEGAL!

Yeah, in your one state out of 50.

Good Ol' Commi-fornia

one of the myths I think they explored VERY throughly tho, was the cell phone at the gas station.. being a ham.. we all know that 1/4watt transmit power isn't going to cause an arc of any significance. I've Tx'd with far more power then that in a gas station with a bare stainless steel antenna...
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G3RZP
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« Reply #16 on: February 03, 2011, 12:21:32 AM »

Over here, the business with gas stations and ignition was when CB was illegal and people found that running 200 watts or more when refuelling sent the pump mad and it under-registered the amount of fuel.

Years ago, there was a paper at a radio conference here from Sheffield University on the subject. There is a certain amount of energy necessary in a spark to ignite fuel or vapour, and it's a lot more than 1 watt. But it's a modern myth.
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KC8IUR
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« Reply #17 on: February 03, 2011, 04:51:56 AM »

20kv potential is necessary to arc through air.
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KI4SDY
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« Reply #18 on: February 03, 2011, 08:27:39 AM »

Where do you get a permit for a "solar death ray?"  Shocked
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KC8OYE
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« Reply #19 on: February 03, 2011, 12:10:19 PM »

Where do you get a permit for a "solar death ray?"  Shocked

a buddy of mine had a 300w motorola and he'd dead key going over the scales at the scrap yard and it would make the scale read high by a thousand pounds or better.. making him look heavier then he was.

it didn't take the yard long to figure out that there was no way he had thousands of pounds of scrap in a 1/4 ton truck tho.. lol
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N1DVJ
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« Reply #20 on: February 03, 2011, 02:20:48 PM »

Just because it failed on mythbusters doesn't mean squat.  Most of their experiments are entertainment for show, and NOT a valid test of the myth.  They pick one aspect of it and make it appear to be the global definition of something working or not.

But they are entertaining...

Back in the 60's when I was in grade school I was a real geek.  One of my favoring books (other than the Brains Benton Mysteries, and Sherlock Holmes too) was 'Solar Science Projects.  Had a lot of neat things in it.  One of which was a 'solar cooker'.  A 'dish' you made out of posterboard cutouts.  Could grill a steak in a pan, even with the sloppy focus.  All it took was posterboard, foil, and a glue stick.  Then there were things with a 14" fresnel sheet you could get from Edmonds back then.  Slip it over a bee on a clover, then raise the lens and the bee would vaporize...


one of the myths I think they explored VERY throughly tho, was the cell phone at the gas station.. being a ham.. we all know that 1/4watt transmit power isn't going to cause an arc of any significance. I've Tx'd with far more power then that in a gas station with a bare stainless steel antenna...
But there IS a real danger with cell phones at gas stations.

Gas vapors COULD (not will, but could) reach dangerous concentrations near the ground from spills under certain conditions.  The danger is not from talking, but from DROPPING the phone.  There COULD be the potential for a spark if the battery is knocked off WHILE the phone is being used, as it strikes the ground.
« Last Edit: February 03, 2011, 02:25:06 PM by N1DVJ » Logged
N0SYA
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Posts: 369




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« Reply #21 on: February 03, 2011, 02:24:42 PM »

ever since that show i cant take anyone with a goatee or van dyke seriously, especially if they wear a beret
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If you have a clumsy child, you make them wear a helmet. If you have death prone children, you keep a few clones of them in your lab.
KC8OYE
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« Reply #22 on: February 03, 2011, 02:59:26 PM »

Quote

But there IS a real danger with cell phones at gas stations.

Gas vapors COULD (not will, but could) reach dangerous concentrations near the ground from spills under certain conditions.  The danger is not from talking, but from DROPPING the phone.  There COULD be the potential for a spark if the battery is knocked off WHILE the phone is being used, as it strikes the ground.


i seriously doubt that.. most cell phone batteries are only 3v, and there just isn't enough potential energy in 3v to ignite fuel vapors.  Mythbusters intentionally shorted a battery in a chamber filled with the most combustible ratio of  fuel and air... that failing, they intentionally removed the safety's in the batteries and tried again... again, just not enough energy.

the single biggest danger in a gas station is STATIC electricity...namely getting in your car and getting back out, and not properly grounding yourself to the pump body before grabbing the nozzle.
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N1DVJ
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« Reply #23 on: February 03, 2011, 03:45:43 PM »

I wasn't talking about a shorted battery.  I was refering to a phone with a 'slide off' battery pack being disconnected while under load.  And I didn't say it WOULD ignite the vapors, I said it COULD.  Chances are slim...
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KC8IUR
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« Reply #24 on: February 04, 2011, 07:14:58 AM »

Added to that, I haven't seen a phone with a slide off battery since the late 90's.
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AA4PB
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« Reply #25 on: February 04, 2011, 07:40:43 AM »

Regardless of the type of phone, I suppose there is always the "slight chance" that it could ignite if you dropped into a puddle of gas on the ground.  I guess there is also the "slight chance" that the hose will break and spray gas all over your hot muffler. You might also shut the car door on your finger. Not to worry - the gov't will protect us from it all. Grin
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N1DVJ
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« Reply #26 on: February 04, 2011, 09:12:07 AM »

Well, I HAVE personally seen phones dropped at filling stations.  Before bluetooth ear pieces became common, it seemed people would try to run the pump while the used their shoulder to hold the phone.  You can do that with a 500 or 2500 sets, but not most cellular phones.

I've NEVER heard of an accident, but like I said, the pieces are there and it COULD happen.
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KC8IUR
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« Reply #27 on: February 04, 2011, 02:23:57 PM »

Monkeys could fly out of my anus. There's no documented case of a cell phone igniting a gas station. Ever.
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W6RMK
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Posts: 660




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« Reply #28 on: February 05, 2011, 03:51:58 AM »


one of the myths I think they explored VERY throughly tho, was the cell phone at the gas station.. being a ham.. we all know that 1/4watt transmit power isn't going to cause an arc of any significance. I've Tx'd with far more power then that in a gas station with a bare stainless steel antenna...



the fire in the gas station problem was NOT from RF...  This goes back about 7-8 years..

At the time, the theory was that it was from a spark/short in the battery of the phone, back when phones had removable external batteries (so you could have spares on a charger, just like with a HT).  Unlike HTs, the phone batteries had much higher energy densities (and there are just more cellphones than HTs) and when dropped, there are scenarios (not entirely plausible, I might add) where the phone and battery could partially separate, causing a short circuit in a battery pack with a high short circuit current, etc.

The other reason they have the "turn off phones while using the gas pump" signs is that they want you paying attention to pumping gallons of a volatile fuel, not talking on the phone. 

While there aren't any documented cases of cellphones actually proven to start a gasoline fire, there are plenty of case of people driving off with the nozzle still in the filler when the driver leaves while talking on the phone.  And those breakaway hose replacements aren't cheap.

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N2EY
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« Reply #29 on: February 05, 2011, 05:27:00 AM »

There's no documented case of a cell phone igniting a gas station. Ever.

I think the issue isn't that the RF or the battery will cause a fire.

I think the issue is that cell phones are distracting, and that you do NOT want to be distracted while pumping gasoline. Or driving.

You see it all the time - people talking on a cell, or texting, and not paying attention to what they're doing. Usually they get away with it; sometimes the results aren't pretty.

What ticks me off the most is that, way back in the '80s or so, there was a lot of noise made about "multitasking". About how we should be able to do several things at the same time.

And so people got the idea that doing just one thing at a time was old-fashioned. It meant a person was stupid, lazy or both.

Now it turns out that "multitasking" often means "doing several things poorly at the same time.

But now we have to get people to pay attention to what they're doing.

73 de Jim, N2EY
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