Author Topic: F.C.C. Order: R.F. Exposure Safety Standards Rules Now Apply to US! MUST READ!  (Read 10841 times)

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Offline W1RC

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If you are reading this you may have recently learned that the F.C.C. has made some changes to the R.F. exposure safety standard rules as they NOW affect ALL RADIO AMATEURS including YOU.  They went into effect on Monday, May 3rd, 2021.

These radio frequency energy exposure limits and measurement requirements are not new; they have been in place since 1 January 1998 for all services except some amateur radio stations because back then the League was able to get many of us ?categorically exempted?.  Nothing lasts forever and so what?s new for us is we radio amateurs are no longer exempt and, henceforth, we will all be required to ?perform an R.F. environmental evaluation? to determine the ?Maximum Permissible Exposure? (MPE) initially and whenever we make changes to our transmitters or antennas.  This simply means we will either take measurements of our station RF field levels using a field strength meter or perform simple calculations to determine the RF exposure levels on all bands and with all antennas you will be using to transmit. You will then record these figures and keep them with your licenses or in your log book as part of your station?s required paperwork thus having this information on hand if requested by the F.C.C. 

The good news is that your station may be ?grandfathered?, albeit temporarily, in which case you will continue to be exempt.  However, the free ride only lasts until May 3rd 2023 after which all stations will be required to measure or calculate their RF exposure levels as detailed above. This includes mobile and portable stations.  However, even if you may still be exempt I strongly advise you to perform these calculations now even only to make yourself familiar with them and to see how simple it really is.

First thing to do is refer to the Power Thresholds for Routine Evaluation table below from 1998.  As of May 3rd, 2021, it is obsolete except to determine the following.  If your station was operating on these bands prior to May 3rd, 2021, with less than the maximum listed power levels for each band you are considered ?grandfathered? until May 3rd, 2023 UNLESS you make any changes to your transmitters, power amplifiers or antenna setup in the interim. Should this occur it means that you will have to comply with the new requirements immediately.

You may refer to the NEAR-Fest R F Exposure Safety Standards Technical Library below.  However my advice is before you dig into it and probably become completely overwhelmed by all the technical data, complex math formulas and bureaucratese one will encounter therein you first might want to take a quick look at one or two of the several calculator apps that will help you determine your RF exposure levels in order to remain compliant with the F.C.C. Order.  This calculator is online so you can try it now and see how it works:

Here?s how to use the RF Exposure Calculator1: Fill-in the screen form with your transmitter?s AVERAGE operating power2 (in Watts), select the emission Mode Duty Cycle (SSB, CW, FM,AM, etc), Transmit Duty Cycle (amount of time when you are transmitting) your antenna gain (over dBi)3, and the operating frequency (in MHz).

Here is a coaxial cable line loss calculator that is very useful to help you calculate your average power at your antenna:

Depending on how far above ground the RF source is located, you should also consider ground reflections as well ? just check the box. 

Then click ?Calculate?. 

Now read the results:  the Maximum Allowed Power Density is expressed in milliWatts per square centimeter (mw/cm2), and Minimum Safe Distance.  This calculator shows it in feet but others will show it in meters.  You will see results for both Controlled Environment and Uncontrolled Environment. A Controlled Environment is an area where the persons exposed to RF are aware of the exposure and its effects (you, your family, your home).  An Uncontrolled Environment is an area where the persons exposed to RF are unaware of the exposure and its effects.  An Uncontrolled Environment is where the persons exposed to RF are unaware of the exposure and its effects (your neighbours, the public, everyone else). 

Write down the Maximum Allowed Power Density and the Minimum Safe Distance numbers for each band and antennas at your station in your station logbook in case you are ever asked. That?s it.  That?s all.  You will not have to do this again unless you change your transmitter or amplifier output power or antenna configurations.

If you perform this evaluation using the highest power level, highest mode and transmitter duty cycles on each band and antenna combination that reading should suffice for reduced parameters for the same setup.

I hope you can see now that this is not really that complicated when all is said and done. Whether you are a ?Tech-in-a-Day wonder or an old-timer you should be able to handle this bit of technical housekeeping without too many tears and frustration. 

Further information can be found here:

Finally, before we all start blaming the League for letting this sneak up on us please consider that even though the R&O was released in December 2019 the F.C.C. only announced in April that the rule changes would be implemented as of May 3rd.

Kudos to Dan, W1DAN, Ria, N2RJ and Ed, W1RFI for their assistance and all the other engineering types who actually understand all this technical language and bureaucratic verbiage for explaining it to us.  You have just read everything you need to know here. 

I also want to thank N6NB, Wayne; K1TR, Ed; W4/VP9KF Paul; amateurs who wrote the calculator programs, and to K7LWH, the Lake Washington Club, in Kirkland WA whose project is to help 9-12 year olds earn their Amateur Radio License which I am sure you will agree, is a most worthwhile enterprise.

We will (hopefully) be hosting a forum/symposium on the subject at NEAR-Fest XXX, scheduled for October 15th and 16th 2021 at the Deerfield NH Fairgrounds.  Hope to see you there!


MisterMike, W1RC
Copyright 2021 Last update 10 May 2021.
May use freely if attributed to the source.

1More calculators you can download....

Ed Parsons, K1TR. This is a Windows program:
Excel spreadsheet -
Wayne Overbeck, N6NB: RFSAFETY
Paul Evans, W4/VP9KF Web-based calculator:

The N6NB/Lake Washington Club calculator now includes the duty factor emission type in the screen fill-in form.  However some do not in which case refer to Table 2 below to see how to make an average power estimate.  Use 40% of your carrier power for CW,  20% of your Peak Envelope Power (PEP) for SSB if you don?t normally use speech processing, 50% with speech processing and 100% for all other modes.  Finally, there is an average transmit % time (0.0 to 1.0 times power) that is also factored into the power value.

3Antenna gain is expressed two ways. Decibels over a dipole antenna (dBd) is +2.15dB over an Isotropic (dBi).  An isotropic is a theoretical antenna which radiates power uniformly in all directions but doesn?t exist in the real world. However antenna gain is often expressed in dBi and I am not quite sure why.  Perhaps it is good old American marketing!

4When downloading this you may see a malware warning or it may be blocked.  We are working on an alternative method to download it.  However if it comes from N6NB?s web site it is malware free.

It?s all in FCC OET 65b supplement:
Specific information for radio amateurs (OET 65b):

Shameless word from your sponsor:
SEE YOU AT NEAR-Fest XXX  ?Grand Homecoming?  Friday, October 15th 9:00 AM and Saturday, October 16th 2021 at Deerfield Fairgrounds, Deerfield NH (03037)!

Offline W1RC

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Three R.F. Exposure Calculators Explained and Reviewed.
« Reply #1 on: April 30, 2021, 04:45:19 PM »
I have received several requests for more information on the RF Exposure safety calculators that I am listing so I have compared and evaluated five of them here.  They are listed in no particular order.  They are all free of charge to use and many are in the public domain so you may distribute them but not for profit. One had a ?bug? and I contacted the developer who fixed the problem and made some improvements.  Another was onky available as a BASIC program and, again, the developer worked with me to update and improve his program so it now runs under Windows 10. They all work bery well and are simple to use so take your pick.

The first two are Web-based, one is an Excel .xls file and two are downloadable .exe files that runs nicely under Windows, even v10!
This calculator is a project of the Lake Washington Ham Club in Washington State,and is based on Prof. Wayne Overbeck, N6NB?s RFSAFETY BASIC program from 1997 described below.  The program has been recently updated and now includes operating mode based duty cycle and percentage of transmitting time calculations. NThe ?form? also asks for the antenna gain expressed in dBi so remember to add 2.15dB to your antenna gain spec if it is a dipole or other antenna whose gain is expressed in dBd. Wayne?s latest update is available below as an executable file that runs very well on all Windows versions up to and including Windows 10.
Written by Paul Evans, VP9KF:  The user interface is very clean and the calculator works well.  Paul?s instructions and explanations of average power calculations are clear and they explain the operating mode duty factor and the percentage of transmitting time factor because the average power estimate has to be figured out in advance of using this calculator.  This one also asks for antenna gain expressed in dBi so essentially you will need to add 2.15 dB to your antennas specification if it is expressed in dBd.

These two apps and spreadsheet calculator are downloadable and the computer does not need to be connected to the Internet in order to use them.

RFSAFETY.  Originally a BASIC program RFSAFETY written by Prof. Wayne Overbeck, N6NB, and published in CQ VHF magazine in January, 1997.  It has just been updated (May 2021) and includes power averaging (what percent of the time do you transmit?) and mode-based duty cycle corrections (e.g., key-down modes versus CW/SSB).  It will do a routine evaluation very quickly and print out a hard copy for your records.  The program tells you if your station is compliant in both controlled and non-controlled environments.  This program was reviewed for accuracy by the staff of the Office of Engineering and Technology at the FCC; it can be used with confidence to do routine evaluations.  Download it from Note: Because this is an .exe file your browser/virus software may give you a couple warnings, quarantine the file or even block the download.  We are working on a safe download method.

PWR_DENS, written by Ed Parsons, K1TR, is a nice, compact downloadable Windows application that runs well under Windows 10.  It may be downloaded at   Unzip and run the executable file.  Easy to use and you don?t have to be online when upu run it. The input screen asks for antenna gain in dBd and does the appropriate power caclulations. Also the program will print the results of the test which you can keep with your station records.

This next calculator from is an .xls file so you will need a spreadsheet program like Excel on your computer.    The thing I like about the spreadsheet is it tells you if your station is compliant in both controlled and non-controlled environments.  The downside is you need a spreadsheet pgm like Excel on your computer to use it.

More RF calculators:

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Shameless word from your sponsor,
SEE YOU AT NEAR-Fest XXX  ?Grand Homecoming?  Friday, October 15th 9:00 AM and Saturday, October 16th 2021 at Deerfield Fairgrounds, Deerfield NH (03037)!

Offline W1RC

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The NEAR-Fest R.F. Exposure Reference Library and Learning Resources.
« Reply #2 on: May 04, 2021, 09:53:39 AM »
The NEAR-Fest R.F. Exposure Reference Library

Here are some links and resources to help you understand this better and make the necessary calculations in order to be compliant.  The documents indicated with an asterisk * are highly recommended.

* RF Safety and You by Ed Hare, W1RFI. (PDF): Ed is the ARRL Lab Supervisor and an expert on R.F. Safety measurement among other things technical.  Must Have.  Download his 1998 book at

You should be aware that the information on categorical exemptions is no longer valid but the other material is as relevent as it was when the book was originally published.

* ARRL RF Exposure Rules Applicable to Amateurs after May 3rd 2021 FAQ
This document is being updated.

FCC Office of Engineering & Technology Bulletin OET 65:

* FCC Office of Engineering & Technology, Supplement B to Bulletin OET 65 (OET65b)
Specific information for radio amateurs.  THIS IS THE ONE YOU WANT!

* ARRL RF Safety info: 2019

From 1998:

American Cancer Society RF Safety information:

RSGB (UK) RF Safety:

Presentation by Dan, W1DAN, ARRL Technical Advisor, Eastern MA Section 5/4/2021.

Presentation by Ria, N2RJ ARRL Hudson Division Director

Presentation by N9GL: 

F.C.C. R&O all 166 pages of it......... released December 3rd, 2019. 

Last, but not least if you run into trouble:

ARRL Technical Information Service (TIS):

Please send comments to

SEE YOU AT NEAR-Fest XXX  ?Grand Homecoming?  Friday, October 15th 9:00 AM and Saturday, October 16th 2021 at Deerfield Fairgrounds, Deerfield NH (03037 for GPS)!