If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Does anyone know the specific model the IEEE and FCC guidelines are based on?
For example, if I have a isotropic emission from my phone's WiFi, does the safety limits supersede normal regulatory guidelines.
The phone section: 17dBm at 2450 MHz we get roughly Pt = 50mW into the antenna Antenna is a Gt= +-1dB gain matched 3.2mm * 1.6mm * 1.3mm ceramic style chip
This chart says 1mW/cm*2 in uncontrolled settings:
Given: wavelength of about L=0.12m distance from human skin to antenna of R=0.05m assumed skin is around Gr = 0bBi
And used the ideal calculator from here:
Max Received power Pw = (Pt*Gt*Gr*L^2)/((4*Pi*R)^2) Pw=0.0023 Watts (or 3.6dBm) thus, a little over double the safety limits...
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
part 2, as unable to edit my own post... :/
Now if I increased distance R=0.077m Pw=0.001 Watts (or = 0dBm) Or seems to fall within the safety margins...
If I used a Planar Inverted-F antenna, than near field behavior is unlikely isotropic making it even more ambiguous. Any corrections in my approach would be welcome, as it has been awhile since I encountered the problem.
Registered Member #230
Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284
Yep the phone companies know this this is why the inband limit for phones is much higher as they think you are only going to be on it less than 15 minutes per day. do not stand near one of those masts with the panel antennas for cell big sites are up in the multi kW with all carriers on at once
Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
Convert dBm to dBi, every 3 dBi you double the distance, work function type things, might not be ionized, its still not enough to release alpha,gamma,xray or beta, so cancer is out, maybe eyes and head have extra heat that will need to be protected from.
I don't think you can use the Friis equation to calculate a power density mentioned in the FCC regulation. The Friis equation tells you something about the total power received by an antenna and uses an effective receiving aperture (see Step 4 in the derivation). The power density is given by Step 2.
For an isotropically radiating antenna Gt=1 and the power density is simply the total power Pt divided by the sphere surface 4*pi*R^2, i.e. 50mW/314cm^2 = 0.16mW/cm^2. That's at a distance of 5cm.
Generally antennas don't radiate isotropically, though, a better approxiamtion is a dipole field. That depends much on the type of antenna. Also the near field (R less or around lambda) of the antenna is stronger than the radiative field, so one should account for this too. That's more complicated and has to include interactions of skin and flesh with the antenna near field.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
completely anecdotal ... a friend and colleague of mine used to service and repair equipment in an amateur radio shop, when amateurs go 'silent key' the family often sell equipment to the shop, and my friend could recognise who's equipment it was as he knew most amateurs in the area. Talking to relatives he discovered that at least two 2m (typ. 5W@145MHz) walkie-talkie users had cancer in the right side of the head !
Neither of us use handheld transmitters (including cellphones) near our bodies, and especially not near our heads. I did a little research some years ago; I believe that ionisation is unlikely, thermal damage is likely at high power densities, and MITOSIS can be affected by surprisingly small electric fields.
To add to the confusion, I just found this article
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Maximum Permissible RF Exposure FCC Regulations
