"Spin" wrote in message
...
I read that an AM BCB radio station transmits through a vertical antenna.
If this is true why does the signal diminish when i turn the ferrite rod
antenna & radio receiver in a vertical position?


A ferrite rod antenna responds to the magnetic-field component of the radio
wave radiated by the transmitting station.

All significant AM medium-wave and long-wave stations use one or more
vertical conductors as their transmitting antenna and the current passing
through this conductor generates a magnetic field. The current path is
vertical so the resulting lines of magnetic force are loops surrounding this
vertical path - that is, loops in planes parallel to the surface of the
earth. Some distance away from the transmitting antenna, the outgoing radio
wave can be described by a magnetic field component aligned the same as
these loops, that is horizontal lines at any point of inspection, or by an
electric field component aligned perpendicularly, that is vertical. By
convention, the 'polarisation' of a single radio wave is the direction of
its electric field component and vertical polarisation is used for MW/LW
because it yields much better range for the same power than horizontal
polarisation (which would try to develop an electric field on the surface of
the conducting earth).

To couple power out from this radio wave requires a coil or loop to draw
current from the magnetic field or a dipole to derive voltage from the
electric field (from which to draw current). A coil couples to a magnetic
field when the lines of magnetic force pass through it ... so your ferrite
rod antenna works best when it is aligned with its axis horizontal.

Chris

.... let the flames begin!