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RF Safety

How Close is Too Close

 
by: John 'Miklor'
July 2016

 
 
 
Your Home Owner Association doesn't permit outside antennas, so you want to mount one inside your residence.  You are aware the RF floating around could be a hazard but how much is too much?

One of my antennas is a Nagoya UT-72 mag mount here in the computer room. It sits above my computer console mounted on a large cookie sheet as a ground plane. It's about 10' away.
 
I picked this distance based on this"
        Amateur Radio RF Safety Calculator

My parameters were:
     Power - 50W
     Distance from center of antenna - 10' (3m)
     Antenna Gain - 2.2 dBi
     Frequency - 150MHz

Based on the results, the recommended distance is 4.3 to 9.6'  (1.3 to 3.0m), so I placed it at 10'

If you are running an HF rig with an antenna in the attic, here are Average Power Estimates to factor in.
 
Operating Mode Duty Factor
Morse Code (CW) 40%
SSB 20%
FM 100%
RTTY/Digital 100%
AM 100%
 
This calculator will serve as a guide for recommended safe distances.
It is claimed to be accurate for handheld radios based on their disclaimer below. 
 
"This program is intended for approximate far-field calculations. It may overestimate the actual field strength of high-gain antennas in the near field."
 
When it comes to RF Safety, always error on the side of caution and safety.
 
 
 

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