"Understanding VHF Propagation" by Rohde and Schwarz

Thanks to John, EI7GL, for posting details of this YouTube video. Anything which suggests that VHF propagation is almost never "line of sight" is OK with me.

A link to John's site is on the side bar. It is a very useful place to look for the VHF enthusiast. 

Cover image from the presentation. See links below.

OK, so some of us think we might already know something about this topic. Maybe. But I certainly benefitted from seeing some things in a different context. Others may wish to look at it.

I learned that duct widening causes lower frequencies to be included in tropo ducts as time goes on. Now I had experienced that tropo ducts are "downwards" (I heard them first on higher frequencies, say 1296, then 432, then 144MHz over time), whereas sporadic E is "upwards" (starts on 50, then 70, then 144MHz). What I didn't know was why this applied to tropo ducts. So I learned a few things.

I knew that sometimes raising my antenna can lose a duct, whereas other times it can get me into a duct. So I had no idea that there were two forms of duct (surface and elevated), and now I know what that might mean for me.

It was good to see it suggested that because no certain mechanism for the sporadic appearance of Es events exists, then prediction of Es events will be a pretty futile exercise.

And it was also good to see a correct time for peak meteor activity. The presentation agrees with the texts that from about 04:00 to about 08:00 local time is the best (not "around dawn" as some sites say, which is too limited even this far north).

So I learned some things, and some things were confirmed, and some things were reinforced.

This video is not intended for radio amateurs, but it does a good job for our hobby nevertheless.

If you are interested you can find it by searching YouTube for "Understanding VHF Propagation" by Rohde and Schwarz.

I will try to post a link here too  https://www.youtube.com/watch?v=DTXJ3bS2UcE

73 Jim

GM4FVM