Range tests with HamShield: LoRa Edition (440MHz, 1 Watt Version)
There is a lot of hype over LoRa and its purported range. As an amateur radio operator and commercial radio professional, I cringe every time I hear the word range. I have seen "up to 20 miles" advertised for unlicensed 100mW variants in the 900MHz band. However, in my testing, this is absolutely absurd and impossible. Unless you have an antenna on the top of a tall tower or mountain, you will probably see about half a mile or less at ground level. Still pretty good, but not 20 miles.
Now, instead of a puny 100mW, lets lower the frequency to the 70cm / 440MHz band and give it a good 1 watt. And to go even more crazy, lets put that into a 13.5 dBi Yagi. That's 25 watts EIRP of chirp spread spectrum goodness.
Then, we will pick the absolute worst, most terrible conditions possible:
- LoRa configured to sacrifice distance for increased speed
- Dense forests in a rural area
- Antennas at ground level (6 feet off the ground)
- Flat area with no elevation gain, forcing all RF to go through forests and houses
- Moving vehicle through all these obstructions
- $70 13.5 dBi yagi antenna
- $25 Amazon magmount antenna
Okay, so maybe we gave it a chance with our yagi. While I have tried a ground level discone antenna to one of our Smiley antennas laying in the seat of a car (and got a couple miles), we will step it up a notch with this setup.
Our software was very simple, we configured our Arduino as a LoRa beacon, transmitting this over and over: "KC7IBT,HamShield: Lora Edition".
The results were a little surprising. Driving around the area, we received many transmissions from our beacon for miles on end. Through dense forests, houses, and all sorts of obstructions. The weakest signals were between -124 and -130dBm, some which a signal to noise ratio of -20 dB! Now that is impressive.
Our furthest copy was at Cape May Airport and vicinity, which was 6.5 miles away. Not only was it absolutely, definitively, in all senses of the word, not line of sight, (with likely 6 miles of contiguous forest) there were some serious fresnel zone violations, which was 96% obstructed. That's right, the zone was 140 feet wide in its center. All of these factors tell us it shouldn't be possible. Although, likely due to the extremely weak signal required for an approximately 3000 bps transmission.
We will have a video soon showing our little adventure. We will also raise the antenna to roof height, and see how far we can push LoRa. This may be the next big thing in high speed, weak signal transmission in Amateur Radio. It may also completely replace APRS. Stay tuned.