On Sun, 27 Jul 2003 22:16:15 -0500, "Richard" anom@anom wrote:


"Elmer E Ing" wrote in message
news:VM_Ua.12050$ff.5596@fed1read01...
Oh boy -- lets assume an antenna is totally resistive -- 50 ohms or
better
still a dummy load of 50 ohms that exhibits no inductance or capacitance.

Now since Power in watts = I squared R where I is the current and R is a
pure 50 ohm resistance
transpose and solve for I = square root of P over R

I get about 4.9 amperes RF current

now

E=I times R so 4.9 times 50 = 244 volts RF volts

That's what you should see at the antenna. Try that on old knucklehead.

With any inductive reactance or capacitive reactance --- different ball
game.

Gurus check my math please

RF power is not electrical power.
As audio power is not electrical power.

Square root of P or 1200 watts in our case = 34.641
34.641/50 = 0.6928 amps.

E=IIR

(0.6928*0.6928)*50 = 23.99 volts.

Therfor, the wire can easily handle the power.
Use of a calculator helps.
Your theory was correct. The decimal point was not.




Elmer's calculations were correct.

Power(P) = voltage (E) x current (I), and
voltage (E) = current (I) x resistance (R)

so... P = I * I * R

and I = square root( P / R )
= sqr( 1200 / 50 )
= sqr( 14 )
~= 4.898979 Amps

and E = I * R = 4.9 * 50 ~= 245 volts

RG-58C/U (Belden 8262) is rated at 1,400 volts RMS. The 20 AWG center
conductor of RG-58C/U (Belden 8262) is good for about 6 amps RMS.

Ref:
http://ecom.belden.com/static/ZZBLDN...TA.HTM?P0=8262


73 de Leigh W3NLB