LoRa Distance Record

[Blaise]

OK, here's one for the folks that actually understand how EM propagation works in practice:

A couple of years ago, the current distance record was set for LoRa at more than 800 miles.  The communication was between a fishing boat and one of the buoys in its fishery across open ocean.  https://www.thethingsnetwork.org/article/new-lora-world-record-1336-km-830-mi

Frankly, I'm confused as to how that happened when, by my best guestimates, the unit on the buoy has a horizon at around 4 miles.  The one on the boat, due to its greater height, had a horizon at more like 15 miles, but that still doesn't make it better!

Now, I was under the impression that signals in the 800-1000 MHz range sere strictly line of site, with neither ground nor sky propagation.  Nonetheless, this event would imply that either I'm completely wrong about how EM propagation works, or somebody's fibbing...

[SteveShannon]

7 minutes ago, Blaise said:

OK, here's one for the folks that actually understand how EM propagation works in practice:

A couple of years ago, the current distance record was set for LoRa at more than 800 miles.  The communication was between a fishing boat and one of the buoys in its fishery across open ocean.  https://www.thethingsnetwork.org/article/new-lora-world-record-1336-km-830-mi

Frankly, I'm confused as to how that happened when, by my best guestimates, the unit on the buoy has a horizon at around 4 miles.  The one on the boat, due to its greater height, had a horizon at more like 15 miles, but that still doesn't make it better!

 

Now, I was under the impression that signals in the 800-1000 MHz range sere strictly line of site, with neither ground nor propagation.  Nonetheless, this event would imply that either I'm completely wrong about how EM propagation works, or somebody's fibbing...

UHF is line of sight until it is reflected or refracted by some atmospheric condition.  Google Tropospheric Ducting.

Physical features such as mountains can also cause reflection or refraction.

[WRYZ926]

Our GMRS repeater is at least 100 miles away from any other repeater that uses the same channel and tones. I am 80 miles away from the other repeater. Normally there is not any issues. But when tropospheric ducting happens, one of the other repeaters can be heard at full strength and will also key up our repeater. 

I have another GMRS repeater that is 50 miles west of me. On occasion I talk to a guy that lives 150 miles east of me on that repeater that is 50 miles west of me. It's amazing how far you can reach when atmospheric conditions are just right.

This goes for any band/frequency from HF all the way up to 900 MHz and higher.

[Blaise]

Ahh!  So it was just luck of the draw...

Well, I suppose that still really validates the strength of the technology.  A milliwatt transmitter that can be detected 800 miles away under *any* circumstances seems pretty impressive...

[Blaise]

*Researches*

 

Holy shit!  Of course the atmosphere has different refractive properties depending on density!  With all the "Fields and Waves" bullshit they shoved into my head, I have no idea how I never realized this.

 

The atmosphere is a gradient prism...

[WRYZ926]

Here is another example of how changes in the atmosphere effects UHF radio waves.

My bother and I both have Allstar nodes and both were set to the same frequency and PL tones. These nodes only put out about .05 to 1 watt of power on transmit. And we have our radios set to 5 watts or less when using the nodes. We are 19 miles apart and 5 watts is normally not enough for us to hear each other.

The other day there was a storm cell in between us and we could hear each other. My brother was using his Allstar node to talk to guys in Texas. I could hear him but not the other people. He could also hear me when I was using my node. The storms and low cloud cover was bouncing the 5 watt signal 19 miles. Granted neither one of us had a very strong signal as the signal strength meters barely moved, but it was enough of a signal that we could hear each other.

We both ended up changing the frequency that our Allstar nodes use to stop this from happening.