[Elecraft] Was Amplifier

[Edward R Cole]

Brian,

First off,its apparent you did not look at the program I gave the 
link to.  Had you done that you would see factors for modulation, 
duty-cycle, antenna gain, etc.

Next,I could not recall the FCC paper: OET 65B, but VK3UM based his 
spreadsheet on this paper a similar papers done by European 
authorities; note the "safe"levels differ between which gov't 
authority is used.  The FCC did thorough study and came up with the 
guideline since they realized not all parties had the equipment or 
expertise to measure near-field RF power density.  Thus the 
simplifying guide which will generally suffice.

More likely one can enter a few known parameters about their station 
vs a total field density measurements.

I was responsible for 62 FCC commercial licenses and seven 
transmitting sites, so I did the FCC calcs by hand with calculator 
way before Doug wrote his  EMR program.
Also did mw safety measurements in the 1970's at NASA Goldstone 
Facility.  The 25mw/cm^2 measured at two miles would not pass today's 
limits.  85-foot dish pointed at you running 20KW CW at 2115 MHz.

I too have experience effects of mw radar testing with open waveguide 
(3kW peak).  Took about ten minutes to start getting a 
headache.  Then I threatened the stupid tech doing that with certain 
bodily injury if he did not use the dummy loads - duh!

I merely wanted all you on the list to know of this handy resource 
for calculating your RF exposure per gov't standards.  Its a minimum 
to try for.

73, Ed - KL7UW



Date: Fri, 07 Apr 2017 16:27:18 +0000
From: brian <alsopb at comcast.net>
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Was Amplifier
Message-ID: <58E7BDE6.1000107 at comcast.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

"Considered dangerous" isn't quite right.  The jury is out of the exact
danger levels of RF for all the various frequencies.  These distances
are more of an accepted limit that protects you from inquiries regarding
RF exposure.  Pointing to the distances being met helps get you off the
hook.

People will be surprised to see how small the distances these
calculations are-- especially at lower frequencies.

One note often overlooked. The distance is defined as the distance from
feedpoint (usually center) of the antenna.

Also the duty cycle can be considered in the calculation.  There are
stock duty cycles for SSB and CW given in the documentation.

Antenna gain may have to be included.

It used to be that anything at 100 watts and below at HF was exempted.
I believe that has changed.

73 de Brian/K3KO


73, Ed - KL7UW
   http://www.kl7uw.com
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