Topband: 160 One Way Propagation

[KN4LF, Thomas Giella]

Tom W8JI Said:
I've never experienced "one-way propagation" on 160 without noise,
QRM, or the radiated power on one end of the path easily
explaining it.

Thomas KN4LF Says:
There is a 160 one way propagation phenomena and it's tied to the E-F Layer
ducting/E valley propagation mechanism.
Most mediumwave frequency RF signals in excess of 3100 miles is via the E/F
layer ducting and/or E Valley propagation mechanism. High solar flux values
can aid in long haul medium wave propagation in excess of 3100 miles, as a
high solar flux value ensures a strong E and F layer duct mechanism.
Typically a transmit antenna takeoff angle must be under 30 degrees to enter
the E-F layer duct.

High solar activity in the form of increased ionization created by
ultraviolet and x-ray radiation can fill in the E Valley region with
absorptive ionization and interfere with the E-F layer ducting mechanism. In
a sense the E-F layer duct is shut down and the mediumwave frequency RF
signal only propagates between the E layer and land/ocean surface, with a
higher angle and more loss.

This temporary shutdown of the E-F layer duct on one end of a propagation
path only, creates the main but not only one way propagation phenomena on
160.

However W8JI's premise is basically correct, as most all seeming one-way
propagation on 160 can be explained by QRN,
QRM, or the radiated power on one end of a propagation path.


73,
Thomas Giella, KN4LF