VHF Radio Safety

[StickFish]

There has been lots of radio discussions going on the Salty Dogs lately and I thought I'd cross post this.

With all the talk on radios lately - I thought I'd add one more to the pile of stuff for us boat owners to be aware of. All two way radios transmit RF radiation with the intended purpose of communicating with others. RF radiation is a form of energy that can be absorbed by human tissue and bone (not to mention the other animals on our vessels). That radiation is absorbed and the effect is tissue heating.

The most sever form of tissue heating occurs in our microwave ovens which we use to heat our snacks and other food items. Microwave ovens operate for the most part at 2450mhz using continious wave (CW - same mode used for Morse Code by the way).

Title 47 Part 80 which is the Federal Law that governs the Marine Radio service contains a specific section relating to RF safety on board vessels.

47CFR80.83 states, "Protection from potentially hazardous RF radiation.

Any license or renewal application for a ship earth station that will cause exposure to radiofrequency (RF) radiation in excess of the RF exposure guidelines specified in Sec. 1.1307(b) of the Commission's Rules must comply with the environmental processing rules set forth in Secs. 1.1301-1.1319 of this chapter.

While the law deals with license or renewal applications which for the most part none of you have it doesn't negate the attention we should have for ensuring that RF exposure on our boats is minimized.

As an Amature Radio Licensee, I had to perform RF safety calculations to insure that people could not be exposed to unsafe levels of RF radiation at my home and mobile radio stations. While planning the installation of my Marine VHF radio I became just as concerned.

Our VHF rigs can transmit a maximum of 25 watts. I'm installing an antenna with 4dbi of gain. Using the following web site I'm able to determine in a controlled environment (My boat) people need to be at least 3.76 feet from my antenna when using 25 watts.

RF Safety Calculator

I had been planning on locating that antenna a tad closer to my operating location in the boat - not any more. With the 8' that a lot of you use on the ocean (I would to if I had a salty boat) the distance is 4.72 feet.

Something important to note about the distance is in any direction to a person. I consider my boat to be a controlled environment - uncontrolled is like an antenna structure in my back yard where I have no control over people other than a fence. On my boat I can ask people to stay away from the antenna.

For those of you planning Marine SSB installations the same web site can be used to calculate exposure levels. For instance a 150 watt SSB signal on 4.096mhz using a 23' Shakespeare 390 antenna (Gain is Unity or 1) you must be at least 2.93 feet away from the antenna.

I hope this is useful to everyone -