On Sun, 09 May 2004 17:26:05 GMT, Dave Shrader
wrote:

Taking Cecil's example a step further. The radiation resistance [Rr] of
an 8 foot antenna at 3.9 MHz is in the range of 1 to 2 ohms depending
upon coil location. The antenna losses, I^2*R, can be in the range of 10
to 20 ohms [Ra], and the ground losses can be in the range of 10 to 20
ohms {Rg]. So, your nominal '50 ohm load' is comprised of Rr + Ra + Rg = RL.

So you can use the formula I^2*R (which is for finding P) without
knowing the variable "I" to find the resistance (Ra)?

I don't think so. Unless you have a magic wand, Harry Potter :-)

Ron


Efficiency is (Rr/RL)*100%. So, 2/50 = 4% or 1/50 = 2%. Take your pick!

The energy is NOT reflected back. It is wasted as heat in the antenna
and ground losses!

Deacon Dave, W1MCE
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