Many articles books and standards have been written on lightning protection. But even if you do it next to perfect if will still disrupt services. See http://stichting-vitaalpendrecht.nl/2014/05/10/blikseminslag-in-toren-waalhaven-in-beeld/ which took out local Radio broadcasting and 3G/4G service showing once again that it’s next to impossible to protect fully against a massive direct hit. However you can minimize collateral damage. Implementing lightning protection can get quite expensive but you can learn from the principles, see what’s done by professionals and then see what’s doable for yourself.
The mantra in lightning protecting is grounding, grounding and…grounding. But ground properly.
So start with an Antenna with an internal DC short and mount it on a pole which is thoroughly grounded with >= 25 mm2 wiring. Of the Antenna’s mentioned above only the Procomm has this short. Now the Procomm is a bit costly but it’s perfectly possible to make something yourself which has a DC short. The Rothammel Antennenbuch has plenty of ideas and even a folded dipole with a 1:4 balun can be grounded in the middle to meet the DC short requirement.
Another alternative is the “fietspomp” antenna which is a half lambda radiator fed by a quarter lambda stub, open on the top to match the radiator, shorted at the bottom. Impedance matching is done by tapping on the quarter lambda stub at the 50 Ohm point
Next is grounding the Coax cable. That usually only get’s done for long run’s with a maximum distance of 20 m between grounding collars.
After this when you need to go inside a building put an Over Voltage Protector outside at the building border and ground it with a cable kept running along the outside of the building.
Huber & Suhner makes real nice Over Voltage Protectors but they are not cheap. Count on 200 Euro’s minimum, see http://literature.hubersuhner.com/Technologies/Radiofrequency/Lightningprotection/?Page=66 Now the LORA band is very close to a cellular band so you might find something usable on E-bay. If you have the choice pick one based on the pure quarter wave principle The ones with a gas discharge tube are second choice since:
- They have a higher rest voltage;
- If you suspect it has handled a strike the gas discharge tube should be replaced. (Nobody does ).
But also here a bit of mechanical ingenuity can save money. A shorted quarter wave piece of good coax like RG214 or 1/2" Cellflex in parallel to the Coax feed line and properly grounded works just as well. Make sure to take the velocity factor of the cable into account and keep the cable grounding this device at the short also outside the building.
Now if you want to keep the Gateway outside, an Antenna with a DC short to ground, fiber optics data line and an isolated power supply is a good way of doing things. (Look closely at a cellular site, that’s exactly what they do!)