fact it's how I get my home internet.
Me to.
I used 2.4ghz band for years. (5 miles 8km) When it rains or there is a fog then there is no connection. Almost never rains.
Now I have moved to 5ghz band and it works in the rain.
----why----
Micro wave cooker works at 2.4ghz. Water adsorbed energy at 2.4ghz. Good radio band indoors. Has some problems outdoors. As you can see we are using it outside.
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I have internet in my "green house". One end of the connection is a stand router, no special antenna. The other end has a 2.5 foot dish from satellite TV. I removed the antenna form the dish and put a standard router there. Strong signal at 1km.
---edited----
The "mesh" network will not need a large antenna. If you have a radio every 1km and you can not talk 10km, then the radios can talk to each other.
Example: Radio-0 can talk to Radio-1 & 2. Radio-2 can talk to Radio-0,1,3,4. Radio-4 can talk to Radio-2,3,5,6. etc. So if you broadcast a message "I am Radio-0 and I want to talk to Radio-10" The message will hop from 0 to 2, 2 to 4, 4 to 6, 6 to 9, 9 to 10. You do not need to know how the message gets there. Yes this will be a little slow. In my case; if I want to turn on water valve-9, a delay of 1 second is nothing.