# Road sign -'Turn Off Two-Way Radios and Cellular Telephones'?
**URL:** https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166
**Category:** Factual Questions
**Created:** [August 26, 2013, 1:07am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166 "2013-08-26T01:07:13Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Smapti](https://boards.straightdope.com/u/Smapti)
#### Post date: [August 26, 2013, 1:07am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/1 "2013-08-26T01:07:13Z")
While driving along I-90 from Seattle to Ellensburg yesterday, and again on my return trip the following day, I saw orange diamond signs (temporary ones close to the ground, not on poles) with the above message on them while traveling through Snoqualmie pass. There was only one sign with the instruction on it in each direction, with no corresponding sign saying it was safe to turn them on again.
I never did turn mine off, mainly because I was using it as a GPS at the time, and as far as I can tell I suffered no adverse consequences as a result thereof. What could be the purpose of such a message? Assuming I’d been pulled over and my phone wasn’t turned off, would I have faced any penalties for having disregarded the sign?
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### Author:  [@running\_coach](https://boards.straightdope.com/u/running_coach)
#### Post date: [August 26, 2013, 1:12am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/2 "2013-08-26T01:12:40Z")
One reason I’ve seen was blasting nearby. Radio controlled detonations.
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### Author:  [@Nametag](https://boards.straightdope.com/u/Nametag)
#### Post date: [August 26, 2013, 1:13am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/3 "2013-08-26T01:13:36Z")
Blasting. The reason for the state law requiring this is fear that a an electronic detonator might be activated by consumer devices that broadcast radio signals. There is no chance that this will happen, but the law is still on the books…
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### Author:  [@Fubaya](https://boards.straightdope.com/u/Fubaya)
#### Post date: [August 26, 2013, 1:14am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/4 "2013-08-26T01:14:02Z")
It’s usually due to blasting for construction in the area.
[This article](http://www.katu.com/news/local/Overnight-blasting-to-begin-on-Highway-43-197778031.html) says it wouldn’t really set off a blast but the signs are required under some old law. Of course, that’s just a county spokesman quoted in the article, I wouldn’t bet my life on it without a second opinion.
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### Author:  [@Driver8](https://boards.straightdope.com/u/Driver8)
#### Post date: [August 26, 2013, 1:47am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/5 "2013-08-26T01:47:37Z")
I guess I think of this the same way I would turning off your phone on a plane: if there was a real risk of this causing a crash or an unexpected explosion they’d have to setup road blocks, perform thorough searches of everyone’s vehicles and confiscate all phones found.
If they just rely on a sign (or on a plane telling people to turn them off without checking) a huge number of people are going to have powered on phones, and planes would be falling out of the sky and construction crew workers would be detonating all over the place.
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### Author:  [@smithsb](https://boards.straightdope.com/u/smithsb)
#### Post date: [August 26, 2013, 2:32am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/6 "2013-08-26T02:32:36Z")
Cell phone - probably never. Someone with a juiced up Ham or CB signal - maybe but the latest equipment - caps and receivers - have better rejection and higher thresholds of initiation.
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### Author:  [@picunurse](https://boards.straightdope.com/u/picunurse)
#### Post date: [August 26, 2013, 3:28am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/7 "2013-08-26T03:28:51Z")
They were doing some blasting over Snoqualimie pass for the last several days.
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### Author:  [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)
#### Post date: [August 26, 2013, 4:30am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/8 "2013-08-26T04:30:03Z")
> [@Fubaya](#):
>
> …I wouldn’t bet my life on it without a second opinion.
Well, but you may really only be betting someone else’s life, because the guy setting the charge may be close enough to receive your signal but not so close that you’d be caught in the blast radius with him. 🆒
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### Author:  [@racer72](https://boards.straightdope.com/u/racer72)
#### Post date: [August 26, 2013, 11:38am UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/9 "2013-08-26T11:38:09Z")
> [@Driver8](#):
>
> I guess I think of this the same way I would turning off your phone on a plane: if there was a real risk of this causing a crash.
I went through a training class last week at my employer, Boeing. Yes, there are documented cased of airplanes having problems due to interference with consumer electronics. That was the reason for the class, I am now certified to test HIRF (High intensity radiated fields) on Boeing aircraft.
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### Author:  [@SmartAlecCat](https://boards.straightdope.com/u/SmartAlecCat)
#### Post date: [August 26, 2013, 1:17pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/10 "2013-08-26T13:17:28Z")
> [@racer72](#):
>
> Yes, there are documented cased of airplanes having problems due to interference with consumer electronics.
Cite?
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### Author:  [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)
#### Post date: [August 26, 2013, 2:39pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/11 "2013-08-26T14:39:52Z")
When I visited the [Arecibo Telescope](http://www.naic.edu/general/), I was told at the facility gates to turn off my cell phone because radio signals from it might interfere with sensitive instrumentation they had running. It was just applicable to the observatory grounds though - no problem at all having it on in [Arecibo](http://en.wikipedia.org/wiki/Arecibo,_Puerto_Rico) itself or on the mountain roads between the town and the telescope, though I don’t remember service being exceptionally good anyway.
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### Author:  [@leahcim](https://boards.straightdope.com/u/leahcim)
#### Post date: [August 26, 2013, 3:00pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/12 "2013-08-26T15:00:59Z")
> [@robert\_columbia](#):
>
> When I visited the [Arecibo Telescope](http://www.naic.edu/general/), I was told at the facility gates to turn off my cell phone because radio signals from it might interfere with sensitive instrumentation they had running. It was just applicable to the observatory grounds though - no problem at all having it on in [Arecibo](http://en.wikipedia.org/wiki/Arecibo,_Puerto_Rico) itself or on the mountain roads between the town and the telescope, though I don’t remember service being exceptionally good anyway.
There were similar issues at the Dominion Radio Astronomy Observatory. In addition, gasoline-powered vehicles were not allowed within a certain range because of the emissions from their spark plugs (diesel was OK), and the on-site staff couldn’t have a microwave in the kitchen.
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### Author:  [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)
#### Post date: [August 26, 2013, 3:22pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/13 "2013-08-26T15:22:29Z")
> [@leahcim](#):
>
> There were similar issues at the Dominion Radio Astronomy Observatory. In addition, gasoline-powered vehicles were not allowed within a certain range because of the emissions from their spark plugs (diesel was OK), and the on-site staff couldn’t have a microwave in the kitchen.
If I was managing there, at some point I’d be tempted to start ratcheting up new restrictions just to see how far I could mess with people.
[ul]
[li]Employees may not use sweetener in their coffee.[/li][li]Employees must wear pirate hats to distribute static electricity, and touch them together while in conversation.[/li][li]Employees may not use more than three vowels in one sentence.[/li][/ul]
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### Author:  [@racer72](https://boards.straightdope.com/u/racer72)
#### Post date: [August 26, 2013, 3:24pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/14 "2013-08-26T15:24:19Z")
> [@SmartAlecCat](#):
>
> Cite?
[http://www.boeing.com/commercial/aeromagazine/aero\_10/interfere\_textonly.html](http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html)
Read the part about loop resistance testing. That is what I was certified to do.
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### Author:  [@Doug\_K](https://boards.straightdope.com/u/Doug_K)
#### Post date: [August 26, 2013, 4:18pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/15 "2013-08-26T16:18:08Z")
> [@racer72](#):
>
> [http://www.boeing.com/commercial/aeromagazine/aero\_10/interfere\_textonly.html](http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html)
>
> Read the part about loop resistance testing. That is what I was certified to do.
From your link:
> [@](#):
>
> As a result of these and other investigations, Boeing has not been able to find a definite correlation between PEDs and the associated reported airplane anomalies.
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### Author:  [@XanderCrews](https://boards.straightdope.com/u/XanderCrews)
#### Post date: [August 26, 2013, 5:54pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/16 "2013-08-26T17:54:15Z")
I’ve driven by NASA Goldstone and there were signs to turn off FM radios, but no mention of cellphones.
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### Author:  [@UncleFred](https://boards.straightdope.com/u/UncleFred)
#### Post date: [August 26, 2013, 8:36pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/17 "2013-08-26T20:36:56Z")
> [@smithsb](#):
>
> Cell phone - probably never. Someone with a juiced up Ham or CB signal - maybe but the latest equipment - caps and receivers - have better rejection and higher thresholds of initiation.
You may be on to something here. Cell phones are limited to about 3 Watts transmit power.
However, CB sets can be 5 watts.
And going back further in time, to the 40’s and 50’s, this article;
> **[DIRECTORY OF MOTOROLA POLICE RADIO EQUIPMENT 1942-](http://www.wb6nvh.com/Moto42/Moto42.htm)**
says mobile radios used of the 'Broderick Crawford" variety (i.e. police, fire, public safety) may have been as high as 50 watts.
So there may have been a chance of mobile radios causing a problem. It may have been a conservative action to post those laws. Though they may no longer be necessary, it could be hard to get old safety laws repealed.
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### Author:  [@UncleFred](https://boards.straightdope.com/u/UncleFred)
#### Post date: [August 26, 2013, 8:47pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/18 "2013-08-26T20:47:45Z")
This article
[ ](http://www.arrl.org/img/file_types/missing.png)
says mobile ham radios can be in the 10-50W range.
(I have no idea how old the article is…)
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### Author:  [@Arthur\_See\_Clarity](https://boards.straightdope.com/u/Arthur_See_Clarity)
#### Post date: [August 27, 2013, 2:03pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/19 "2013-08-27T14:03:41Z")
> [@Tom\_Tildrum](#):
>
> If I was managing there, at some point I’d be tempted to start ratcheting up new restrictions just to see how far I could mess with people.
>
> [ul]
> [li]Employees may not use sweetener in their coffee.[/li][li]Employees must wear pirate hats to distribute static electricity, and touch them together while in conversation.[/li][li]Employees may not use more than three vowels in one sentence.[/li][/ul]
how could you miss the opportunity to have people seriously (in their minds) wear tin foil hats??
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### Author:  [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)
#### Post date: [August 27, 2013, 2:52pm UTC](https://boards.straightdope.com/t/road-sign-turn-off-two-way-radios-and-cellular-telephones/667166/20 "2013-08-27T14:52:29Z")
Interesting anecdotes. One question I have is, “What’s the penalty?” Does anyone know what can happen to you if you have a radio transmitter (e.g. CB radio, cell phone) on too close to an observatory or other non-aircraft related sensitive area? Can you be charged with Aggravated Radio Transmission with Intent to Interfere with Science? Is it not a crime but the observatory can sue you for the grant money it lost because it couldn’t find any quasars? Is it not a matter of law at all but the observatory could ban you from the observatory grounds itself if you won’t turn your phone off?
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