Topband: 160 One Way Propagation

[Tom Rauch]

> There is a 160 one way propagation phenomena and it's tied to the E-F
> Layer ducting/E valley propagation mechanism. Most mediumwave

Who has heard that phenomena in some manner that strongly 
indicates it happens? Certainly I haven't!

> 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.

I think what you are really trying to say is there must be adequate 
field strength at angles lower than around 30 degrees, not that the 
takeoff angle must be 30 degrees or less. Takeoff angle is 
commonly accepted as the angle where maximum radiation 
occurs, and is almost useless for talking about performance at a 
given angle other than the maximum.

For example, I can have an antenna with a TO angle of 50 degrees 
that has more radiation (field strength) at 20 degrees than an 
antenna that has a TO angle of 15 degrees.

> 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.

So if this "duct" shuts down...how can a signal can arrive without a 
signal launched from the arrival point being able to go on the 
reverse path??

Having worked with this stuff most of my life, I've never seen a one-
way path of any type. What physical mechanism causes the path 
to be unidirectional?
73, Tom W8JI
W8JI@contesting.com