[IRCA] Isotropic is the topic and the inverse is worse!

[Charles A Taylor <MWDXer@xxxxxxx>]

At 08:19 PM 7/4/2007 -0700, you wrote:
>Hi Charles
>
> > I think you can legally do 100 mW at 1720 kHz.
> >
> > Anyone know anything contradicting that statement?
>
>http://a257.g.akamaitech.net/7/257/2422/13nov20061500/edocket.access.gpo.gov/cfr_2006/octqtr/47cfr15.223.htm
>
>Section 15.223 (link is above) says "The field
>strength of any emission within the band 1.705-10.0
>MHz shall not exceed 100 microvolts/meter at a
>distance of 30 meters". There are some exceptions, of
>course.
>
>Question: if the limit is 100 microvolts/meter at a
>distance of 30 meters, using the inverse square law,
>would that be roughly the same as 3 watts at the
>antenna?
>
>
>Hope this helps
>
>73 de Joe AB8YP

Joe,

I'm not sure what you mean here.

Using an "isotropic" (point-source, perfect) antenna, you'd get far
more than 100 uV/m at 30 meters for 3 watts.

Just on a guess, maybe 1 V/m.

When I pirated and got 2.6 mV/m at 1 mile, I used the equations for
an isotropic antenna and calculated we were getting 86 mW ERP.

That's for 10 watts into the antenna.

Pretty miserable efficiency for having a poor radial system.

As I wrote to Almost Lost Mike at Los Alamos Quiere Decir Más De
Un Alamo (Y Nada Más), Nuevo Méjiko Gulch Negev Desert: field
intensity varies as the inverse of the distance.

Charles
Assistant Professor in Hoptoad Valve Technology,
University of Grinder's Switch, Tennessee



   Charles A Taylor, WD4INP
  Greenville, North Carolina 



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