Quote from N6CMB - Chris on 05/11/2020, 1:38 PM

So, it's ducting?

https://www.youtube.com/watch?v=2aoN0s-eafE

 

But ducting is propagation... right?

Propagation : prop·a·ga·tion

transmission of motion, light, sound, etc. in a particular direction or through a medium.

"the propagation of radio waves through space"

Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather. In this propagation method, when the signal encounters a rise in temperature in the atmosphere instead of the normal decrease (known as a temperature inversion), the higher refractive index of the atmosphere there will cause the signal to be bent. Tropospheric ducting affects all frequencies, and signals enhanced this way tend to travel up to 800 miles (1,300 km) (though some people have received "tropo" beyond 1,000 miles / 1,600 km), while with tropospheric-bending, stable signals with good signal strength from 500+ miles (800+ km) away are not uncommon when the refractive index of the atmosphere is fairly high.

Very interesting subject to study!

Quote from Cold War Jesus on 05/16/2020, 6:59 AM

Hi Chris,

No, ducting is not propagation. The ITTU generally states the RF signals must be reflected off layers of the earth’s atmosphere etc. to be considered propagation.....so that doesn’t include VHF and higher frequencies.

Cheers......Rod

Quote from N6CMB - Chris on 05/20/2020, 9:19 AM

It seems a bit like semantics.... but I can't argue with the ITTU!  🙂