Hi Rbbarral,
I found the receipts for the dozen or so antennas that I ordered back in Feb of 2021. I matched up the photos from the websites to the actual antenna that I’m currently using on my rover and as near as I can tell, this is the best onmi-directional LORA antenna (it specs refer to it as a 5db antenna) for me and my area. Your mileage may vary.
I found that directional (9 to 13 db yagi) antennas would perform better, but they became too bulky and hard to carry though our difficult terrain (wooded mountains). Perhaps a yagi would be a great choice in your area, just be sure to point the Rover’s directional antenna directly towards your base (you can use the standard Emlid antenna at the base). You can mix and match antennas: you can use an omni-directional antenna on the base, and you could use a highly directional antenna on the rover (or vice versa) - just be sure you understand antenna polarization and directional patterns.
While you can mix and match Omni-directional and Directional antennas, be sure to keep the polarity of the antennas the same. If you’re using a vertical antenna at the base (e.g. the Standard Emild antenna) be sure to keep your rover’s antenna oriented in a vertical direction (and NOT horizonal)
A directional yagi antenna(s) can also be a great choice where you’re doing a “point to point” survey (such as setting just one control point miles from a base station) or a “point to small area survey” (such as setting a group of points in close proximity to one-another from a single base location). The yagi will concentrate all of the power in a narrow beam, both horizontally and vertically:
The above image shows that usable beam width (the RED line) of the antenna is only about +/- 10 degrees from the direction the antenna is pointing. If you’d put this antenna on the base and the rover, and carefully point one antenna to another, you could greatly increase the distance between the 2 radios. As soon as you move out of the usable beam width (the area inside the red lines), signal strength will decrease very quickly.
I only work in the mountains of southern New Mexico, where terrain varies by +/-500’ or more on any given day, so I’ve found the standard Emlid antenna to work best on the base (the Emlid antenna produces a signal pattern that resembles a ball - a low gain antenna will radiate power in all directions.) The standard Emlid antenna gives a good horizontal and fair vertical signal. If I were to put a higher gain omni-directional antenna on the base, it would produce a higher gain in the horizontal directions (greater distance horizontally), while sacrificing signal strength in valleys (less signal strength above & below the horizon).
Feel free Google “onmi-directional antenna patterns” for some great images of various db antennas. Be sure to look at both horizontal and vertical radiation patterns if you work in hilly / mountain area.
If you’re working in the “flat lands”, you will most likely benefit from the above mentioned 5db antenna on both the base and rover. Perhaps a 7db or 9 db omni-directional antennas on on one or both units would help if terrain is really flat, just be sure to get the base antenna at reasonably high point (10’ or more above nearby obstructions) and a clear of all line of sight for maximum range.
As a real-world example how much the antennas matter, I have installed about 100 Ubiquiti directional (parabolic dish) antennas for point-to-point communications. Using no more power that your average home wifi wireless router (which has about a 100’ range on a good day), I can use a pair of Ubiquiti 24 db dish antennas & radios to send the signal 10 miles or more with no problems (at 200 Mb to 1 Gb speeds). Of course, the beam width of the antennas is very narrow, and pointing of the antennas is critical. For such long distances and low power, line-of-sight is essential and you’ll have to carefully consider the Fresnel Zone of the signal (you can google Fresnel for more info).
Simply put, the range you’ll get is all about the Signal to Noise Ratio (SNR) of your application, Line of Sight, & your local area (terrain).
1st REDUCE THE NOISE, you can’t really reduce nearby radio inference (noise), but by selecting the quietest frequency in your area you can double or triple your range. Select the lowest noise channel for your area (this may be difficult without a spectrum analyzer, or some other way to measure the radio interference in your area). FYI, I’m currently experimenting with a low cost (amazon.com), portable spectrum analyzer - more on this later… Also, if you can find an out-of-production 900mhz Ubiquiti WIFI radio (Ubiquiti locoM9 NanoStation 900MHz radio) it has a spectrum analyzer built in.
If you can find a clear channel in your area for LORA, you can double or even triple your range between the base and rover. Unfortunately most folks can’t accurately measure background noise. For a simple example of background noise, manually tune your AM car radio slowly across the entire band about two hours after your local sunset (yes, night time matters). Take your time and you might be amazed just how many faint, distant signals you can pick up on a single frequency. Some local radio stations are really strong, some distant stations are really weak. On some frequencies you’ll be able to pick up 3 or 4 distinct stations on the same frequency. Each and every one of the signals contributes to the noise at that frequency. – Yes, I know the AM band and Emlid LORA operate at different frequencies, this is just an example. You don’t want your Emlid frequency to be the same frequency that a local factory is using in your area. You want your Emlid radio on the quietest channel in your area.
If you don’t have a way to measure the noise in the 900mhz band, you can always try a few different random channels in your area. In my local area, we have a very low noise part of the 900mhz band (I use the spectrum analyzer from my Ubiquiti 900mhz locoM9). On average, the noise is about 6db quieter than all other channels.
Every 3db in noise reduction (or increase signal strength) is roughly equivalent to doubling the power of the radio.
Along with selecting the lowest noise frequency, be sure to use a fiberglass (non conductive, invisible to Radio Frequency) extension pole near your antenna. Metal poles can (and do) wreak havoc with the Radio Frequency signals.
2nd. INCREASE THE SIGNAL STREGTH by using a more directional antenna(s) on either the rover and/or the base (or both). Study antenna radiation patterns (both omni-directional and directional antennas), and match the antenna(s) to your terrain. Too many of the really cheap antenna are garbage, and the don’t live up to their claims. Buy from a reputable supplier(s) and use what works best for you.
By finding the quietest frequency (-6db) and using a better antenna (+5db) on my rover I’ve improved my Signal to Noise Ratio by about 11db (its simple math), that’s roughly equivalent to increasing the power at the radio by about 15 times.
If, for example, I were to add a 5 db omni-directional antenna on the base (with my existing setup), it would increase the SNR to 16 db in the horizontal direction (and power would be reduced in vertical directions), which would be equivalent about 32 times increase in power horizontally and I’d lose signal in the valley (refer to antenna radiation patterns). The directional radiation pattern of the 2nd 5db Omni-Directional antenna on the base would make signal unusable with my steep mountain terrain.
3rd INCREASE POWER AT THE BASE AND/OR ROVER Easier said than done. A few members are have great success with this method. I’m still watching and waiting, with great anticipation.
Good Luck. Be sure to stay legal with your antenna and power booster choices.