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Author Topic: Long distance wifi exposure concern  (Read 258 times)

N2KD

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Long distance wifi exposure concern
« on: February 21, 2023, 07:00:57 AM »

At work the company has installed a Cisco
wifi setup for a security booth approximately 400 feet fom the main building.

Employees were concerned that wifi antenna is about 2 feet from their heads where they sit for hours.

Is this a concern for 2.4 to 5ghz ?

Should the company be doing a exposure worksheet?

Installer had no idea of power, exposure etc
and I figured those on this forum would know
if it's proper practice, or a concern?

Thanks, rc



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K5LXP

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Re: Long distance wifi exposure concern
« Reply #1 on: February 21, 2023, 07:25:23 AM »

You can't assume just by a model number what it's configured for (band(s), power level) so unless you're privy to it's settings, you might have to measure it over the air (spectrum analyzer, incident power meter).  Often EH&S departments will have a simple exposure meter they'll use to ensure compliance to nonionizing radiation limits.  Maybe as a WAG you can do a worst case calculation based on the equipment spec and see if it's even possible to exceed the safe limit.

Mark K5LXP
Albuquerque, NM
« Last Edit: February 21, 2023, 07:33:48 AM by K5LXP »
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WX7Q

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Re: Long distance wifi exposure concern
« Reply #2 on: February 21, 2023, 08:53:39 AM »

https://www.emrss.com/blogs/emr-shielding-solutions-blogs/is-wi-fi-an-emf

Me thinks you need to get this checked out for your own safety and mental health.

Your favorite search engine is your friend.

HTH
WX7Q
Jim
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K9AO

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Re: Long distance wifi exposure concern
« Reply #3 on: February 21, 2023, 10:08:23 AM »

Can you get the equipment model numbers and the antenna model number?
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K7NI

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Re: Long distance wifi exposure concern
« Reply #4 on: February 21, 2023, 06:51:10 PM »

Calculations can be made if you know the conducted output power and antenna gain.
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W7XTV

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Re: Long distance wifi exposure concern
« Reply #5 on: February 21, 2023, 09:16:49 PM »

Calculations can be made if you know the conducted output power and antenna gain.

If the device operates under FCC Part 15.249, as unlicensed WiFi routers do, the maximum field strength is 50 mV/m at 3 meters on both 2.4 and 5.8 GHz.  This calculates to about 0.5 mW ERP into a dipole, or 0.75 mW EIRP.  There is no way this power level can cause any risk to humans in any location or at any distance.  Unless you're clipping the antenna to your ear, that is.  ;D

In other words, don't worry about it.
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WA3SKN

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Re: Long distance wifi exposure concern
« Reply #6 on: February 22, 2023, 02:39:46 PM »

OK, 2.4 GHz would be a concern if working at higher power levels.  However, at router power levels I doubt that there is an antenna combo available that could cause any issues... no matter the time limit.
Have you measured any levels with a meter?  I have seen a lot of hype about this on the internet but the level limits were determined back in the mid 70s and safe levels are now known.

-Mike.
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W1VT

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Re: Long distance wifi exposure concern
« Reply #7 on: February 22, 2023, 02:50:43 PM »

This paper describes how to more accurately predict the near fields for a parabolic dish.
http://www.arrl.org/files/file/Technology/RFsafetyCommittee/ntiatm-90-145%20(1).pdf

One way to minimize exposure is to use a pair of parabolic dishes to focus the beam so a minimal amount of power can be used.

Sometimes you will see this demonstrated at Science Museums.  There will be a pair of parabolic dishes at either end of a yard, allowing two people to communicate over a long distance without shouting.
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K7NI

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Re: Long distance wifi exposure concern
« Reply #8 on: February 22, 2023, 03:42:53 PM »

Calculations can be made if you know the conducted output power and antenna gain.

If the device operates under FCC Part 15.249, as unlicensed WiFi routers do, the maximum field strength is 50 mV/m at 3 meters on both 2.4 and 5.8 GHz.  This calculates to about 0.5 mW ERP into a dipole, or 0.75 mW EIRP.  There is no way this power level can cause any risk to humans in any location or at any distance.  Unless you're clipping the antenna to your ear, that is.  ;D

In other words, don't worry about it.

I'm not sure this is exactly right. I'm not an expert on all of the rule parts but I have looked at the test reports for some WiFi extenders and other WiFi devices that use a 1 Watt conducted limit with a 6 dBi antenna.  Even at that level it would be safe at 20 cm.

If you can get the FCC ID of the device, there is an RF an exposure report asscoiated with it.
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