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I read this article which said I could get upto 50 km with a LoRa module.

But when I read the product description it says the in-built range is only 16 km, so I obviously need an antenna. But what kind of antenna can I use that can get my 16 km LoRa module to 50 km?

Will something like this work?

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It seems that a range of at least 440 km is possible with the LoRa protocol (i.e. there is no time-of-flight assumption as in GSM).

The correct way to answer this question is by looking at the link budget for your transmit/receive arrangement. Although the basic calculations are simple, knowing the right way to do the calculation is not so simple.

To receive a usable signal, the receiver needs a certain signal-to-noise ratio (determined by the tolerable error rate and the modulation characteristics). You may find some online examples of how to calculate this (for LoRa or something similar).

Signal comes from transmit power, plus antenna gain, minus free-space loss (the range calculation) minus any shading from non-line-of-sight, plus antenna gain.

Noise comes from the receive environment or thermal noise (whichever is greatest) and amplifier noise figure, plus any multi-path interference which is not delay compensated in the receiver.

Assuming a 16km range is possible with a simple antenna (spherical uniform radiation), you're asking for a 3.125 times range increase or a 9.77 times increase in power. This is conveniently about 10 dB, so as a rough approximation you need a 5 dB antenna gain above the 'trivial' antenna at each end. If you aim for 7 dB at each end, this gives you a small margin for other factors you've not accounted for, imperfections in your assembly, etc.

A further complication is that the quoted 16km range is plausibly within the horizon of an antenna close to the earth, but to achieve 50km line of sight, you would need to raise one or both ends by many metres.

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    Free space path loss calculations are relatively unimportant unless you have actual line of sight - which typically means talking to an aircraft or mountain top. In more usual applications, obstructions (including the horizon) and interference are the drivers.
    – Chris Stratton
    Jan 20 '18 at 17:58
  • @ChrisStratton in link budget lingo, free space path loss includes the 1/r² term. The difference between total path loss and free space path loss includes the effects you mention. In this very extreme case it's a whopping -317 dB! This is probably the largest actual free space loss ever measured.
    – uhoh
    Nov 13 '18 at 7:35
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    The point was that if you do not have line if sight, that, rather than the free space loss, is the dominant driver, hence the free space path loss is not really that informative. This answer tries to apply a flat unobstructed earth model at distances where only unusual topography or a raised antenna would make that true, so it is for most practical purposes misleading and wrong: the question asker will probably not get what they want, while in neglecting the real issues this incorrectly implies they will.
    – Chris Stratton
    Nov 13 '18 at 13:16
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First, your question is unanswerable by the way as no one could tell what will work in an unknown environment. For example if there is a huge hill between the two modules, or a big city then it won't work. But if your module is attached to a ballon which has an altitude of 38 km, then you are possibly good.

While the balloon was at an altitude of 38.772 km (about 127204.7 feet) somewhere close to the border between Germany and the Netherlands, it was spotted by a The Things Network node in Wroclaw, Poland, at a distance of 702.676 km, or about 436 miles.

But what I would consider this as more realistic data. They achieved roughly 18.3 km with a good line-of-sight and a better antenna than the one you have linked.

  • It may be possible to achieve a greater range, especially with a higher gain gateway antenna [...]

  • For best range performance, line-of-sight or near line-of-sight is desirable. Elevating the gateway antenna (for example, on a building or a mast) is recommended along with a site survey to determine the best location to site the gateway antenna. [...]

  • Range within an urban environment was beyond the scope of this test but 1-2 kilometers (depending on the environment) should be possible in an urban environment with some degree of building penetration.

In summary to increase range:

  • Elevate your antennas.
  • Use antennas with higher gains.
  • Use directional antennas and not omnidirectional ones.

But keep in mind that at the end you will be always limited by the environment.

Here is a quite detailed study about the topic that worth reading.

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    That's a really interesting study and link!
    – uhoh
    Nov 13 '18 at 7:44
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Try a Yagi antenna. Both receiver and transmitter will need an antenna, and they must be aligned with each other (direct line of sight). Just a few degrees of inaccuracy will cause bad reception. There are various DIY yagi antenna guides online, and open source yagi calculator programs that will compute the required dimensions for a 868MHz antenna and balun. You can buy most of the supplies, such as thick copper wire or aluminum rods, at most hardware stores (Home Depot, Lowes). You will probably have to look online for SMA adapters (know the difference between SMA and RP-SMA) to attach the antennas, and decent coaxial cable. If you're going to try it out, I suggest you buy an RTL-SDR ($20USD) for radio debugging. I doubt you will achieve 50km though. If you upped the power level enough to achieve 50km range, at least in the US, you'd probably be violating FCC laws. I think max power is 25mW

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  • An RTL-SDR is not useful for this. While universal (to the point of feeding software LoRa decoding) it is a truly horrible receiver with a dynamic range best categorized as a joke, especially compared to something actually engineered for weak signal work like a typical LoRa chip. Essentially you use an RTL-SDR for exploring nearby signals or downstream of an impressive front end.
    – Chris Stratton
    Jan 20 '18 at 18:00

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