I work exclusively in mountainous, wooded, rugged terrain of southern New Mexico. Line of Sight (LOS) with LORA is pretty much non-existent in my part of the world - at most I’ve got about 300’ of LOS. Between the trees, mountains, valleys and our rugged terrain, LOS is pretty limited. But, I can get well over a mile distance between the Base & Rover with my Emlid RS2s, built-in LORA radios. Just as a suggestion, you may want to look at your Base’s location, your antenna(s) and your local noise level before you start adding external radios, power boosters and other such equipment.
The ability to receive a solid signal at your rover depends upon many factors, including data speed (I use the lowest available data rate on the base & rover), the noise floor (interference from other radio emissions), the location of the base unit, the gain of the antennas, and other such factors.
I’ve been able to get over 1 mile solid RTK with my Emlid RS2s, NON Line of Sight, with 2 mountain tops separating the base & rover with just a few simple and cost effective changes.
First, get your Base up as high as practical, a few extra feet on the base unit helps. Even when my base is located on a mountain top, I always try to add a few extra feet, if possible. Be sure to locate your Base in a clear area, even if it means setting a new ground control point in a better location.
Second, choose the best frequency for your location. I dug out one of my Ubiquiti M900 Loco (nano bridge m-9) wireless network radios (these radios may be hard to find as they are older units). As part of the $200 M900 radio, it comes with a software package which is called “AirView”. Airview is a 900 Mhz Spectrum Analyzer and I was able to determine the noise floor over the entire 900 Mhz band by letting the AirView program run & rotating the M900 radio 360 degrees (the M900 has a built-in directional antenna). By selecting the frequency with the lowest noise floor, I’m able to get 6 db less noise at 914.8 mhz versus the rest of the band (your location will have a different frequency). As noise varies due to local conditions, I’ll be keeping the Ubiquiti M900 in my tool box for times when long distance Lora is the only way to get RTK corrections.
Radio (Lora) is all about Signal to Noise Ratio. To get better reception, you can either increase your signal strength by 6db (which requires 4 times more power at the transmitter), or select a frequency which has a lower average noise level by 6db at the receiver. The 6 db power increase is equivalent to a 6db noise reduction by selecting the best frequency.
Third, consider using a different antenna on the base and/or rover. There are many different antennas available that will work out of the box. The simplest is 5 to 7 dbi onmi-directional antenna. You can get a little more range by purchasing a 9 to 13 dbi directional yagi antenna, but you may have to add your own coax connector to mate with the Emlid. Keep your coax cable short as reasonably possible.
In my case, selecting the best frequency gains about 6db in noise reduction (less interference). Selecting a better antenna at the Rover adds about 10 db (or more) to the signal strength (assuming you point the directional Rover antenna towards the Base). I generally use the stock Emlid Lora antenna at the base, as it provides a great omni-directional signal. You add the two numbers together (6db + 10db) and it equals 16 db, which is equivalent to a 40 times increase in power. If you need more range, you can consider a higher gain antenna at the Base, but you should study the directional pattern of the antenna. High gain antennas can be very directional in their Horizonal and Vertical patterns.
FYI, you may want to buy several antennas from different suppliers, as the quality varies greatly, and so does their real-world performance. Some of the “high gain” antennas that I bought were complete junk.
Radio (Lora) is all about Signal to Noise Ratio. Noise is reduced by selecting the best, local frequency. Signal can be boosted by increasing power or selecting a more directional antenna.
One last tip for the best LORA range, use a fiberglass range pole (or a pole extension) along side the antenna. The metal range poles can (and do) alter the antenna’s radiation pattern and signal strength.
Those of you who choose to increase the power, please share your results and your equipment recommendations.