Atmospheric Ducting

congrats on passing both tests. i learned cw when i was about 13, then had to sit thru the army teaching me AGAIN !! but i got up to 43wpm which i’m sure i’ll attain ever again. I’ve missed extra 3 times i think so far.
addittional: a radio wave ‘bends’ 10% across the surface of the planet.
I have not read "lady be good’’ for many years but I do believe they maintained radio silence on their return from the Polesti oil fields. The flight engineer managed to walk just at 90 miles before he also succumbed. two of the crew has yet to be found in the ever shifting dunes.
Who has seen the new book which supposedly documents WW2 radio signal that was recently heard? The theory being this signal is stuck in F region and continues to propagate? certainly possible i suppose but it’d be pretty weak RF by now!

I’d have been licensed around '65 if not for the code requirement.
My present status is much more due to what I consider the joke tests currently being administered than to my depth of knowledge. I’m not remotely qualified to operate a proper station (though I will be if I decide to become active).

Now that we are at it there is another phenomenon called Diffraction. It is the bending of a wave as it passes an obstruction. Because of diffraction there is some illumination, scatter of the region behind an obstruction or target by the radar beam.

IMG_5419

Diffraction effects are greater at the lower frequencies. Thus, the radar beam of a lower frequency radar as for example a 10 cm radar, tends to illuminate more of the shadow region behind an obstruction than the beam of radar of higher frequency as a 3 cm radar or shorter wavelength.

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Ducting areas.

Area ③︎ is the one where I experienced quite a number of times extensive ducting. That happened on medium wave telephony, we could for instance almost every time we sailed there communicate with the Dutch coastal radio station Scheveningenradio. I witnessed also in this area the radar screen showing the entire map of Italy. It is funny that I cannot remember having met these conditions on my home turf, area ②︎!?

Mediterranean Sea and Persian Gulf are famous for ducting because they tend to have long-lasting temperature inversions.

https://journals.ametsoc.org/doi/full/10.1175/JAM2452.1

Here’s a pointer to a huge trove of papers about propagation. Contrary to what you might think from the link, the particular paper pointed to is the 43d of 45 papers, about radiosonde mapping of ducts. The shipboard radar paper with illustrations on page 105 may also be of interest, possibly along with many others.

https://www.researchgate.net/profile/Karin_Stein/publication/252155585_Impact_of_coastal_environment_on_point_target_detection/links/576a7cbd08ae787b7e5ca6bb/Impact-of-coastal-environment-on-point-target-detection.pdf#page=319

Page 105

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