great explanation! I actually learned something. BTW, my answer was gonna be
,," majic"..


"Jim - NN7K" wrote in message
m...
Nah-- Think is is referred to as " Fresnel Zones", and other
nomenclature- It has to do with multi-path - phase relationships
of the recieved signal- similar to the drive down a country road
at midnight, listening to an A.M. broadcast station (DX) fadeing
in-out - if you measure the distance between the 2 fades, it
equals 1/2 wavelength ! this effect works also in the verticle plane!
and, at vhf- the effect is quite noticeable in the fades (every 40
inchs at 2 meters, and about 18 inchs on 450) has to do with the
multi path signals arriveing in phase, or out of phase (cancelling
each other)! as info-- Jim - NN7K