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I'm trying to plot a radio wave propagation plot of an isotropic antenna. I've found a collection of equations that I've tried to use, but the results that I'm getting, aren't exactly what I expect (not a circle or sphere, since the power is equally distributed).

Here is the equation that I'm currently using.

ReceivedPower(RxP) = TransmitPower(TxP) - FreeSpaceLoss(FSL)

Receive gain is equal to the transmit gain, which is equal to 1 or 0dB.

FSL = -27.55 dB + 20*log[frequency(MHz)] + 20*log[distance(m)]

TxP = InputPower / 4*Pie*Radius^2

TxP = EIRP, Effective Isotropic Radiated Power

So the only variable that I have would be the distance & radius, which I believe to be the same. All the images of an isotropic antenna power distribution demonstrate a spherical (or in a 2d space, a circle with an intensity radiating outwards). Instead I have a spike in the middle of high power, which drastically goes to zero as the distance grows.

My question is whether or not I'm using the correct equations. If so, is this the sort of output that I should be seeing? Lastly, EIRP generates a unit [W/m2], can is this a valid unit to be using to be measuring dB, or is there a conversion that I should be using?

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# Isotropic Radiation Equation

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