[bars] RF Exposure Calculator

[Andy Wallace]

I’m enjoying the questions and answers on this one. Thanks, Bruce!

Speaking of RF exposure…

My boss sent me a 9gag video clip of some guys trying very hard to win a Darwin Award next to a broadcasting tower. I found it on Youtube so here’s the link. Gary, you can probably explain why the voltage node is high at that location. 

Google “plasma speaker” afterwards. 

https://youtu.be/b9UO9tn4MpI

Andy
KA1GTT

On Aug 6, 2021, at 1:18 AM, Bruce Anderson <w1lus at hotmail.com> wrote:


We are all required to calculate the RF exposure to people from our transmissions.
The results should show that our antennas are located far enough from people so no one gets over exposed. 
Or inversely where to locate our antennas to prevent over exposing people to our transmissions.
The ARRL has provided a simple calculator for hams to determine this minimum safe distance.

http://arrl.org/rf-exposure-calculator
RF Exposure Calculator
The FCC has adopted guidelines and procedures for evaluating environmental effects of RF emissions. The new guidelines incorporate two tiers of exposure limits based on whether exposure occurs in an occupational or "controlled" situation or whether the general population is exposed or exposure is in an "uncontrolled" situation.
arrl.org

Below in a sample calculation I did for my FT 8 transmissions on 20 Meters running 100 watts to a half wave dipole.

The results show two feet away for myself and family is safe and 4.5 feet away is safe for Neighbors.
Of course, since the antenna is over 15 feet high there is no issue with this antenna and power on 20 Meters. 

RF Exposure Calculator
Parameters
Power at Antenna: 100 (watts)
Mode duty cycle: AFSK SSB (duty cycle=100%)  (FT 8)
Transmit duty cycle: (time transmitting)
You transmit for 1 minutes then receive for 1 minutes (and repeat).
Antenna Gain (dBi): 2.15 (1/2 wave Dipole)
Operating Frequency (MHz): 14.074
Include Effects of Ground Reflections

Results for a controlled environment:
Maximum Allowed Power Density (mw/cm2): 4.5437
Minimum Safe Distance (feet): 1.9897
Minimum Safe Distance (meters): 0.6065

For an uncontrolled environment:
Maximum Allowed Power Density (mw/cm2): 0.9087
Minimum Safe Distance (feet): 4.4490
Minimum Safe Distance (meters): 1.3561

Bruce
W1LUS

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