I am curious about real life experiences, but also about theoretical thoughts about the following:
If a Gateway is located on a mountain, lets say 500 vertical meters above the surrounding terrain, whats the typical range that can be reached using SF7 (or SF8, 9, a “good” SF)?
If I am not mistaken, the total link budget of SF7 is 137db. Hacking this data into a free space loss calculator results in a theoretical possible distance of about 200km. Of course, this is not realistic. But, seeming more realistic, if the signal has to go through a single concrete wall (20dB absorption), SF7 could still achieve 20km range.
So, regarding gateway placement, it seems to me that a gateway further away but on very elevated ground (lets say 5 or even 10km away from a city) could produce much better connectivity results than a gateway directly in the city but level with the typical building height.
Much better connectivity results in terms of a good spreading factor as well as in terms of better overall coverage.
Dont forget the other factor that influences good reception is SNR - and whilst LoRa is great for subnoise floor signal extraction there are still (SF determined) limits. Height is almost alway best for range but one consequence is a high mounted antenna also then picks up more (additive) RF noise from the surroundings (that’s why broadcast TV/Radio works welll from a hill top transmitter sending out a signal, where cellco’s typically place their (2-way) base stations at lower levels and closer to the target coverage area…
The sensitivity of SF7 is quoted as -123dBm (so a link budget of 137db with 14dBm TX) but its also a requirement that the signal is at no more than -7.5dB below noise, so implying a noise level of -130dBm, which is very low for Earth.
If you want to know how the coverage of a gateway could look like, use TTNmapper. Choose a gateway in a comparable environment and altitude and you will see what should be possible.
E.G. North-East of the town where I live (DE-Cologne, 60m MSL) there is a gateway abt. 400m MSL high in DE-Remscheid. In direction S to NW this gateway has a coverage of more than 50 km.
Or install a gateway and do it yourself by using TTNmapper.
Regarding Noise Floor: I already thought about this, but getting indications about the typical noise floor levels for LoRa proves difficult: I found values from 105 - 120dBm, which makes huge differences for calculations.
What I found interesting is that the noise floor on a mountain does not seem to differ much from urban environments (to be honest I only found one information about this so far) - I would have guessed that the noise floor in a city is worse.
@wolfp@hellebauer
Thanks for the real life information. Using TTNMapper, I was able to see the information for the GW you mentioned and another similar one here in southern germany.
