Our friend Todd K7TFC in Portland found this in the 1950 ARRL Handbook at an, uh, opportune moment. TRGHS. This seems to describe what a I am hearing, especially that "airmass boundary" in the lower left of the diagram above.
I'm not a VHF guy, and I am a bit surprised at the persistence of this propagation path. It is 4:30 am here and the adult contemporary rock from Puerto Rico (Kokomo by the Beach Boys!) is full quieting here in the Dominican Republic. And it is of the same strength during daylight hours. I don't remember this from the winter months, but I may have just missed it.
Here is what AI (Gemini) says about this:
One other factor to consider: The island of Mona is about halfway across the path. There are few people there, and there is almost certainly not a repeater of any kind. But there may be a metal tower or two...
Gianfranco IU1DZZ and Mike WN2A both support the tropo hypothesis. Mike mentions the Hepburn Index. I will have to read up on that. Hamilton is also looking at this propagation path. Thanks guys.
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Bill, Try this site, too:
ReplyDeletehttps://www.ve2dbe.com/english1.html
Roger VE2DBE has a great path analysis software for online calculations. You can spend hours with this site, just register (free!), set up the sites and all the parameters and run it. A couple of minutes later you get your prop analysis. We use it for amateur repeater and simplex work.
For your FM BCB receiver, the wider bandwidth (~200KHz) makes for less sensitivity than typical amateur FM receivers, so just use whatever your FM BCB receiver is rated for. Something like -100 to -110 dBm, typ. Maybe less,~ -115dBm?
73-WN2A