Here is an updated version of my RF Safety Worksheet. There were
no errors in Rev. B (as far as I know), just some enhancements in
this version. I hope you find it useful. Let me know if you find any
Dave Hachadorian, K6LL
SAMPLE RF SAFETY WORKSHEET (Not Officially Sanctioned) Revision C.
(Not for repeater or multitransmitter use) K6LL, author.
A. Callsign: AA7AAA
B. Frequency, MHz: 21.45
C. Maximum PEP transmitter output, watts: 1500
D. Type of feedline: RG-213
E. Length of feedline, feet: 80
F. Feedline loss, negative dB: -.8
Look this up in a book, or use the program TL
G. Line F divided by 10. (It will be a negative number). -.08
H. PEP power delivered to the antenna: line C antilog line G
1500 antilog (-.08) = 1248 watts
Scientific calculator keystrokes:
.08, +/-, inverse, log, times, 1500, equals
Note - Evaluation is not required if line H does not exceed:
160/80/40m, 500w; 20m, 225w; 17m, 125w; 15m, 100w; 12m, 75w;
10/6/2/1.25m, 50w; 70cm, 70w; 33cm, 150w; 23cm, 200w; 13cm and
shorter, 250 watts.
I. Worst case (highest) Emission mode duty factor: .4(cw/proc.
FSK, RTTY, AFSK SSB, FM Voice: 1.0
Conversational SSB, heavy speech processing: 0.5
Conversational CW: 0.4
Conversational SSB, no speech processing: 0.2
J. Transmit/Receive duty cycle over six minutes: .5
Longest conceivable percent transmit time in six minutes,
expressed as a decimal.
K. Transmit/Receive duty cycle over 30 minutes: .5
Longest conceivable percent transmit time in thirty
expressed as a decimal.
L. AVERAGE power to antenna, controlled case: H x I x J = 250
M. AVERAGE power to antenna, uncontrolled case: H x I x K = 250
N. Antenna Gain, dBi: 9.5 (large tribander)
Sample gains from OET Bulletin 65, supp B:
3 el triband yagi 20m/6.5 dBi, 15m/7 dBi, 10m/8 dBi
quarter wave vertical 1 dBi
half wave dipole 2 dBi
1/4 wave vhf/uhf whip or GP 1 dBi
5/8 wave vhf/uhf whip or GP 4 dBi
17 el yagi on 5 wavelength boom 16.8 dBi
Discone 2 dBi
O. Closest CONTROLLED human proximity to antenna, feet: 46
P. Closest UNCONTROLLED human proximity to antenna, feet: 51
Print this worksheet, and Proceed to the University of Texas
Wide Web Site: http://www.cs.utexas.edu/users/kharker/rfsafety
Select "Include Ground Reflections."
Input items L, N, O, B (controlled case). Print the output sheet.
Input items M, N, P, B (uncontrolled case). Print the output
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com