Hi Christopher,
Looking at the lora board it looks like your lora is in the 860-900 Mhz (approx) Range,
the following is not really telling you what to get, as I would need to get all the details of the link(s), the specifics.
Some things need to be kept in mind. the higher the frequency, the more line of site is needed/highly recommended. If you have lots of hills, trees and buildings, it may or may not even be possible for a single hop. You really need to be trying to setup/install things such the line of site (or close to it) can be achieved. This may need a “repeater” to get an end to end link to work as you need; if it can work with the trees/hills and buildings, the lora radio settings needed my end have having very very low speed, which may not be an issue depending on your needs.
The next thing to keep in mind, lora will have Max Power limit set. As such the radio output power will have a fixed upper limit, so the only way to get a power gain (and I use that term loosely) is by antenna gain. But physics gets in the way… When an antenna has gain, what it really is doing is taking the energy from one direction or plain and putting that into a different direction or plain.
Without looking at the antenna radiation patterns for each antenna, as a rule of thump the higher the gain the longer distance you can push the link, at the expense of needing things to be better aligned. e.g. a High gain antenna may push the signal in a more horizontal plan so good for flat ground, but not so good for hills. Beams at each end of a point to point link can be really good, but will need to be correctly aligned.
That said, you may not need the extra power for the distances you need to cover and if you do, a repeater, if possible could be better.
With the coax run, as a rule of thumb, shorter will be better, but some coax is better then others. You can get the specs and do the math an see if it will be an issue or not,
In some of my local playing, I made a portable lora unit, with a small 2dbi omni. (half wave) and a 3dbi on a base antenna.
With that setup, it easily covered 4Km line of site and could go longer based on the signal levels. but I could only just get it to work with 2 houses in the way to about 800m and 3 houses in the way, I could not get to work (over the approx 500m)
So what I hope to have covered is that the answer really is going to be… it depends on you exact needs.
To be able to select an antenna, you/we really need to know the actual path to evaluate the issues along the path. e.g. Amount of trees, can you get line of site, if not how much is blocking line of site and where in the path.
