Ground wave propagation is a fascinating, under-used propagation mode in the ham HF bands. Sure, we all know (or should know) how well it works on the AM broadcast band down around one MHz, where you can receive powerful stations well over the horizon, but does it work up in the tens of MHz? Surprisingly, yes. But don't take my word for it, here are a couple of well-researched articles on the matter:
Radio Waves and Communication Distance (QST, January 1985)
The ground wave part is on the first page under the heading "Close-In Contacts." Particularly interesting is Fig. 1, which shows approximate useable ground wave ranges as a function of frequency. Ten-plus miles from a ground-mounted 6BTV antenna on 10 meters? Sure, I've done it. Surprised me too.
An Empirical Investigation of High-Frequency Ground Wave Propagation (JHU/APL, 1992)
A thorough investigation of GW propagation in the 20–30 Mhz range. There is a lot to unpack there, but it's very much worth the read. Mostly it's about getting over mountains when repeaters and the ionosphere are unavailable.
One application immediately comes to mind: Using an on-the-dirt ground plane 10 meter antenna to "crawl" RF over the hills and into the valleys at the Clear Springs bike trails in the Homochitto NF. It's heavily wrinkled terrain, where both VHF/UHF bands and cell phone coverage are patchy. Take along my FT-817nd on a mountain bike and try to stay in touch with the base, while using "control" 2m/70cm band HTs to show where line-of-sight paths do and don't work. It might make for an interesting ham camp-out this spring or next winter. Will have to mention it around at the next Club meeting.
Thinking about this for a moment, ground wave propagation's ability to roll over and down in between the hills may explain the continuing popularity of CB with the deer hunters and off-roaders. They tend to be practical people who use what works.
Effective ground wave propagation at 10 meters? Looks like, out to 14 miles; YMMV.
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