[sdiy] generators/antennas analogy?

[David Halliday]

What the radio station is doing is figuring out the diameter of where their
signal can be comfortably received and using census or demographic data to
determine the target population within that circle.

This is a statistical number and does not represent an actual head-count of
listeners.


A receiver requires a certain number of microvolts of RF to deliver a clean
audio signal.  The stations engineer knows that a given number of watts into
the antenna will yield a certain number of microvolts at any specific
distance and direction from that antenna.  ( some antennas are directional
and the signal can be "pointed" - others radiate uniformly throughout a
circle )

There is no feasible way to determine the number of receivers "tuned in" to
a station by measuring the signal absorption.



-> -----Original Message-----
-> From: owner-synth-diy at node12b53.a2000.nl
-> [mailto:owner-synth-diy at node12b53.a2000.nl]On Behalf Of Lincoln Fong
-> Sent: Sunday, April 22, 2001 3:29 PM
-> To: Synth-Diy
-> Subject: [sdiy] generators/antennas analogy?
->
->
-> Whilst I am familiar with the idea of 'back emf' in a
-> generator there is
-> something I have never understood which Im sure someone can clear up.
->
-> I once heard that Radio and TV stations can judge audience
-> figures by the
-> amount of power 'absorbed' ie the Watts or MWatts they have
-> to pump out. On
-> one level this makes sense. A popular station would need
-> only the weakest of
-> transmitters if this were not so. But can the resonance of
-> millions of tuned
-> circuits really indicate power usage that accurately? And if
-> not then how do
-> they judge audience figures? I don't really buy the argument
-> that grid power
-> usage can accurately reflect these things when so many
-> programmes start at
-> exactly the same time.
->
-> Lincoln
->