[CQ-Contest] Meeting FCC Guidelines for Exposure to RF Fields

[Fred Laun K3ZO]

Since I have always endeavored to run a fully legal operation, and since I
live in a residential area, I have spent the past two days evaluating 13
different antennas against the FCC Guidelines for Exposure to RF
Electomagnetic Fields.  These guidelines must be observed by USA Amateur
Radio stations beginning 1 January 1998, or four days from now (see 47 CFR
Part 97.13c as amended).  I have a total of 18 antennas, but three are no
longer used, another is used for receiving only, and another is used only
for the VHF Packetcluster by a transmitter whose power never exceeds 45
watts, and is therefore exempt from having to be evaluated under the
guidelines.

I know that most of the people on this list are far more proficient in
technical matters than I am, but in the belief that there may be others who
need to evaluate their antennas quickly, just like I found myself, and that
I may be able to help them save some time by describing what I did, here it
is.  I hasten to add that Amateurs are not required to use the following
method to comply with the regulation, and I'm sure that many have done
their evaluations using the University of Texas Web Site or other methods. 

I have the W5YI Report to thank for showing me the way to get started on
this project.  The issue for 15 December 1997 was devoted almost entirely
to this subject. I learned that the information I needed could be
downloaded from the FCC's Web Site at:  
  
                  http://www.fcc.gov/oet/

What you are looking for there is OET Bulletin 65 and Supplement B to OET
Bulletin 65.  Though I downloaded and printed out the entire documents, a
total of 150 pages or so, all that you really need to perform the necessary
evaluations are the tables on pages 25 and 26 of Supplement B, and the nine
pages of instructions and worksheet pages 2, 4 and 5 of the Optional
Worksheet and Record of Compliance which is found at the end of Supplement
B.  Worksheet Pages 2, 4 and 5 are very "official-looking" and the 13
different copies of this three-page document that I have made up in a
manila folder should sufficiently impress the attorney of any neighbor of
mine who might come nosing around if they happen to hear about the new
regulations.

All of my antennas fell within the guidelines, though the 72-element array
I use on two meters for working auroras passed only because it is
side-mounted and has a limited rotation, and cannot be pointed at my shack
or the homes of my closest neighbors.

A few points which might help you save time:

1) I used the manufacturers' claimed gain figures for my antennas even
though I feel they are excessive in some cases.  For example Telrex claimed
14 dbd. for its 6-el 20 meter Yagi, even though the best the late Jim
Lawson, W2PV, could come up with for a 6-el 20 meter beam was 11 dbi.  I
found that manufacturers invariably rate their antennas in dbd., but the
FCC worksheet uses dbi. to arrive at its evaluations.  You can convert dbd.
to dbi. by adding 2.14 (ARRL Antenna Book) or 2.15 (W2PV).

2) The FCC worksheet uses distance measurements in meters thoughout. You
can convert feet to meters by dividing the figure in feet by 3.28.

A few other points:

-- The FCC worksheet includes factors for evaluating duty cycle and
emission type.  The practical effect of these calculations is to greatly
reduce the effective power that your antennas radiate with respect to the
guidelines, and it makes it much easier for an antenna to meet the
guidelines.  I used the "SSB voice, heavy speech processing" option for my
"emission type" factor, since if the antenna can pass guidelines using this
emission type, it will pass using any other emission type I employ at this
station.

-- There is no substitute for tall towers in meeting the guidelines.  All
of my quads and Yagis are at least 24 meters high and that made it easy for
them to meet the guidelines, usually by a factor of 4:1 or 5:1.

-- "Your League is working for you."  The forward to Supplement B includes
a long list of ARRL staffers who worked on Supplement B, including W1VT and
N6BV who are frequent contributors to this list.

Do not send you results to the FCC!  Just keep them on file in case you are
ever asked to show them.

Good luck!

73, Fred            


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