Add a transmitter Help!
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The Transmitters tab is where you should start. In this tab, you add a transmitter for each one you want to run calculations for. You get to pick the name, but the names must be unique, so if you have three of one radio, give them a suffix or something.

After clicking on "Add a transmitter", you will be prompted to "Add a band" for that transmitter. Just like your real radio, each transmitter here can have its own bands. It will continue to prompt you to add new bands until you hit "Cancel". If you decide at some later time to add more bands, you can manually click on the "Add a band" link inside the transmitter box. Deleting or editing the bands and/or transmitters can be done with those links as well.

As you add the bands, you specify information on how you will be using that band for this calculator. For example, if you typically use 50W on the 80m band while using CW, you should enter that data there. This way, you can model your real-life usage of the radio. In addition, you should enter your usage windows for controlled and uncontrolled exposure. Remember that the controlled exposure window is six minutes long and the uncontrolled window is 30 minutes. These two fields here are not in minutes, but rather in percentage. So fill in the percentages appropriately.

If you are using an amplifier with your radio, you can just assume that the radio is putting out the amplifier's output for the sake of simplification.

You only get to fill out each band once per transmitter, so use the highest power configuration you plan on using. Note that the various modulation modes and exposure percentages will also reduce the total RFE in the calculations.

After adding all your transmitters and transmitter bands, go on to the Antennas tab.

Add an antenna Help!
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The Antennas tab is where you enter information about your antennas. This includes the controlled and uncontrolled distances for which we are making calculations. Also, it gives you a chance to enter the gain for each band that the antenna will be used with.

Click on "Add an antenna" to start with and enter the basic information. The "Ground reflections" entry is whether or not to use the formula to incorporate ground reflections in the RFE totals. I use it, but you should refer to Bulletin 65 for what you think you should do. The controlled and uncontrolled distances are basically how close you and your household can get to the antenna and how close anyone else can get to it.

After saving the antenna, you will be prompted to add bands until you hit the "Cancel" button. This allows you to set the gain for each band. This gain is used in the formulas for calculating RFE. It should be listed as dBi, not dBd. If your antenna specs are in dBd, take the dBd number and add 2.15 to it.

If you need to, you can always go back and add, delete or edit the bands that you have created. When you have entered all your antennas, move on to the Connections tab.

Add a connection Help!
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The Connections tab is where you define the connections that are between your transmitters and your antennas. Each transmitter/antenna pair can only have one connection, but each transmitter can connect to multiple antennas and each antenna can be connected to multiple transmitters, with each connection having different characteristics.

Things that are included in the connection properties are wire type, wire length, tuner losses, and any other losses (lightning suppressors, line splitters, etc.) This allows you to have a wide range of flexibility in accurately modeling your connection setup. All losses are specified in dB, so be sure to enter them that way. If you need to add multiple losses to put in the other losses field, you just add the dB values together.

Currently, I only have specs on a few wire types available, but if you want this application to have more, feel free to send the specs to me and I will add them. Just make sure that they cover a wide range so they can be used on lots of bands.

Add a connection for every physical connection you plan on modeling. You will see a section for each connection in the Results tab.

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The Results tab is where all the results of the calculations are shown for each of the radio/connection/antenna groups that you have specified.

Listed in convenient tables, you see the data you entered in the first few columns and then starting with "Power at Antenna", you see the ERP for each band. Then, using that number, the calculations show the RFE at both the controlled and uncontrolled distances, the minimum allowable distance for each band and then whether or not the band is within the limitations set by the FCC.

For each connection shown in the Results tab, and for each band within those connections, you should make sure that both the controlled and uncontrolled exposures are within the limits. There is a box that will say "yes" or "no" for each entry. If any of the boxes say "no", then you need to look into your setup to see what you can do to reduce the RF exposure for that band. Some options are to:

  1. Use a lower output power
  2. Use a smaller operating window (i.e. transmit for less time in each six or 30 minutes segments)
  3. Use a modulation that is less power (FM is 100% modulation whereas CW is only about 40%)
  4. Use a lower-gain antenna or a more lossy network (it would be a better idea to just turn down the power)
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In the Import/Export tab, you can save your information for another day or copy it to send to a friend. All the data is already stored in your browser (only locally—the application transmits no data back to the server—all the calculations and data are done on the client).

To export, hit the Export button and the data will all show up in a weird looking format that can be copied and saved in a text file. Then you can send it to a friend or use it later.

To import, paste exported data into the text area and hit the Import button. This will try to slurp up all the data and make sense of it. If something goes wrong, it should gracefully die, without destroying what is already on your system.

To clear all the data off your system, press the "Clear all data" button. This will remove all saved settings from this application from your browser, allowing you to start over with a clean slate.

To view some sample data, you can click on the "Reset to sample data" button. This will remove all previous settings and replace them with some canned settings.

Your Web Browser is Not Supported

Sorry for the inconvenience. The N7OH RFE Calculator requires just about anything except Internet Explorer. Rumor has it that it works on IE 8 (and later versions), but you run that at your own risk; I am not able to test that browser. Try FireFox, Opera, Chrome, or maybe even Safari. Whatever you try, make sure it is a new browser that supports HTML 5. In addition, you must have JavaScript enabled for this page or it will not work at all.

Vernon Mauery, N7OH

RF Exposure Calculator - Helping hams understand the mysteries of RF Exposure
Copyright © 2009-2014 Vernon Mauery (N7OH)

The idea originated from the power density calculator written by W4/VP9KF. I started writing my own javascript version only to find that it was really annoying to need to retype everything in each time I visited the page. I wanted something that would store my data. And I wanted to be able to share the application with others, but I didn't want to store their information. I finally learned about local storage with HTML 5 and decided that I could use that for this application.

If you have questions, comments, suggestions, flames or anything else you would like to tell the author, please send an email: [my call sign] at arrl dot net

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see