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*To*: <boston-radio-interest@khavrinen.lcs.mit.edu>*Subject*: Fw: Mexican Radio*From*: "Dan Strassberg" <dan.strassberg@att.net>*Date*: Wed, 22 May 2002 07:31:58 -0400*Sender*: owner-boston-radio-interest@bostonradio.org

----- Original Message ----- From: Dan Strassberg <dan.strassberg@att.net> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Sent: Wednesday, May 22, 2002 7:28 AM Subject: Re: Mexican Radio > Garrett: No. Over a perfect conductor (for the purposes of this discussion, > salt water is close enough), the coverage _radius_ increases as the square > root of the power, but the coverage _area_ is directly proportional to power > (A = Pi r^2). If you hold the antenna efficiency constant, the signal > strength at any point is directly proportional to the square root of the > antenna-input power. That relationship is exact. Moreover, over a perfect > conductor, the signal strength is inversely proportional to the distance > from the transmitting antenna. For medium-wave signals, it turns out that, > with typical soil conductivity, you can roughly (really roughly) approximate > the ground-wave signal strength at any point as inversely proportional to > the _square_ of the point's distance from the transmitting antenna. So > you might say that a 10X increase in power results in a > _fourth-root-of-10-times_ increase in coverage radius and a > square-rooot-of-10-times increase in coverage area, but that relationship > is only a rough approximation, because it depends on frequency and soil > conductivity. The lower the frequency and the better the soil conductivity, > the more inaccurate the approximation. Moreover, because a medium-wave > station's skywave signal stength allegedly does not depend on the soil > conductivity in the vicinity of the transmitter site (a point I question), > the station's _skywave_ coverage area should be directly proportional to the > station's power. > > -- > Dan Strassberg, dan.strassberg@att.net > 617-558-4205, eFax 707-215-6367 > > ----- Original Message ----- > From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> > To: Cooper Fox <fox893@yahoo.com> > Cc: <bri@bostonradio.org> > Sent: Tuesday, May 21, 2002 5:02 PM > Subject: Re: Mexican Radio > > > > <<On Tue, 21 May 2002 13:01:30 -0700 (PDT), Cooper Fox <fox893@yahoo.com> > said: > > > > > Even tho you would have a heck of a power bill... > > > think of what your broadcast area would be!!?? > > > > Wouldn't make much of a difference -- do the math. Even if the level > > of interference were the same (which it would not be), a tenfold > > increase in power would give only a threefold increase in coverage > > area, thanks to the inverse square law. > > > > Most of the big European and North African broadcasters are a megawatt > > or two -- just to get over the noise floor, thanks to all the other > > European and North African broadcasters running hundreds of kilowatts. > > > > -GAWollman > > >

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