Re: "Scotty, Beam me up!"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

This is a useful data point to compare against TC measurements...

30 Volts into 10k is 90 mW.  If you were to assume that the 20 kW were
spread into a hemisphere (which it isn't, but anyway...) you would expect
the power density at 1.5 miles (2.4 km) (36 sq km surface area) to be 552
W/sq km, or about 0.55 mW/sq meter.  A vertical antenna 50 feet (15 m) high
probably has an effective aperture of around 100 square meters (15x7), so a
ballpark figure for the amount of power intercepted would be 55 mW, which is
very close to your measured 90 mW (i.e. less than 3 dB difference... )

The difference can be explained by:
a) The transmitting pattern is not a hemisphere, but is weighted towards the
ground
b) The effective aperture is probably bigger, because of the "image" of the
vertical in the ground
c) You are close enough that you probably aren't in the "far field"
(wavelength is 500 m, so you'd want to be careful at least out to 2*pi
wavelengths, or 3 km)


There are lots of electronic devices that can run perfectly happily on 90
mW...

>
> OK.  Not my idea of wireless "power" transmission, but each unto his
> own tastes.  By the way, I have a 20 kW 1540 kHz BC station about 1-1/2
> miles from here.  When I series tune my 50 foot vertical I can get about
> 250 ma of RF in the series circuit.  If I rectify the voltage across the
> loading coil I can get 30 or 40 volts with a 10 k load.  No violation of
> the laws of nature, though.
>