[Elecraft] Miles per Watt

[Pierre Desjardins]

----- Original Message ----- 
From: "Pierre Desjardins" <ve2pid at sympatico.ca>
To: "S55M" <s55m at siol.com>
Sent: Friday, January 07, 2005 17:39
Subject: [Elecraft] Miles per Watt


> Miles per Watt is nonsense data to impress
> people.because nothing happens in linear mode!!!
>
 Not a linear behavior for sure...

 Lets say that a 500 mW signal at 7,4 mHz is received 4000 km away and that
 both antennas are half-waves dipoles. We could be tempted to say that an 1
 watt signal would reach 8000 km in the same conditions.

 But according to the Friis transmission formula, the first 500 mW signal is
 reduced to 0,00000096 microwatts at the received end, and the second one (1
 watt) is a whooping 0,00000048 microwatts! Still readable? Not sure...

The inverse of the square of the distances is working there, hyperbolic, not
 linear. Twice the power, but the distance doubled,  squared makes 4 and the
 fraction becomes 1/2.

 72/73, de VE2PID
KX1 # 442