This subject comes up every so often, and the answer is basically unchanged from what I wrote a number of years ago. Basically if you are not in the direct beam of a recreational boat radar, and closer to it than 3 meters, there is no danger.
WHO has written a "white paper" on this.
RF fields below 10 GHz (to 1 MHz) penetrate exposed tissues and produce heating due to energy absorption. The depth of penetration depends on the frequency of the field and is greater for lower frequencies. Absorption of RF fields in tissues is measured as a Specific Absorption Rate (SAR) within a given tissue mass. The unit of SAR is watts per kilogram (W/kg). SAR is the quantity used to measure the "dose" of RF fields between about 1 MHz and 10 GHz.
An SAR of at least 4 W/kg is needed to produce known adverse health effects in people exposed to RF fields in this frequency range…..
The power that radar systems emit varies from a few milliwatts (police traffic control radar) to many kilowatts (large space tracking radars). However, a number of factors significantly reduce human exposure to RF generated by radar systems, often by a factor of at least 100:
Radar systems send electromagnetic waves in pulses and not continuously. This makes the average power emitted much lower than the peak pulse power.
Radars are directional and the RF energy they generate is contained in beams that are very narrow and resemble the beam of a spotlight. RF levels away from the main beam fall off rapidly. In most cases, these levels are thousands of times lower than in the main beam.
Many radars have antennas which are continuously rotating or varying their elevation by a nodding motion, thus constantly changing the direction of the beam.
Areas, where dangerous human exposure may occur are normally inaccessible to unauthorized personnel…..
Marine radars can be found on small pleasure boats to large ocean going vessels. Peak powers of these systems can reach up to 30 kW, with average powers ranging from 1 to 25 W. Under normal operating conditions, with the antenna rotating, the average power density of the higher power systems within a metre of the antenna is usually less than 10 W/m2. In accessible areas on most watercraft, these levels would fall to a few percent of present public RF exposure standards.
Add to this that we are not operating our boats, with very low power, but a fraction of the time that a professional mariner would be exposed to radar beams, the risks become far less.
I have at hand, the installation manual for the 4 KW Garmin 24" HD radar which is on my boat: It gives the total beam width of that radar as 25 degrees; 12.5 degrees above and below the direct "horizontal" of the radar mounting--some of us put a wedge under the radar to give a better approximation of the horizon of the boat when underway, and this averages 4 degrees.
The formal warning in the Garmin Installation manual is:
It is recommend that the radar be mounted out of range of personal (horizontal beam above head height). When the Radar is transmitting, do not look directly at the antenna at close range: eyes are the most sensitive part of the body to Electromagnetic energy. When properly installed and operated the use of this radar conforms to the requirements of ANSI/IEEE C95I 1992 standards for Safety.
I have put my radars (total of 6 I have owned) on some short pedestal for several reasons, but none of those related to health. As long as you stay out of the direct beam, there is no documented health risks. All of the studies involving health issues and small radars, have been done with much higher power radars, and with much longer exposure periods than we will ever have with the small units on our C Dory--even the open antennas, which are on a couple of the larger boats.
It is good practice to stay out of the beam, and I do criticize folks who put radars where it is only a few feet from the scanner and either eyes or genitalia--such as an installation on the front face of a flying bridge. Directly under the radar, the amount of energy would be difficult to measure, and should not present any health risks. I use 15 degrees to 20 degrees below the horizon just to be safe.
If you use the Garmin 12.5 degrees, you want your head below the
beam by approximately 5.5" at 2 feet, 11" at 4 feet, 16" at 6 feet, 21" at 8 feet and 26 inches at 8 feet from the center of the radar dome. Taking the super cautious 20 degrees, then these numbers become 9" at 2 feet, 18" at 4 beet, 21" at 6 feet, 24" at 8 feet and 33 inches at 8 feet from the center of the radar dome (which will be about 5" above the bottom of the radar to start with. Of course the further you are from the radar transmitter the less energy will be received.
Marie and I both have cardiac pacemakers which might be susceptible to this energy--and have never had any problems with the pacemakers.
