Someone asked a while back as to whether a LoRa device\module could be improved by adding bandpass filters and\or an LNA.
I eventually got around to writing up some tests I had done, initially at 434Mhz, BW125000 and SF7.
By using software that counts packets sent at different powers you can work out at which point (transmit power) the link fails. You can then make a change, add a bandpass filter, LNA, antenna then run the test again and measure the change in dB.
In summary, adding a bandpass filter made the link worse, due likely to the filter insertion loss.
Adding a high specification LNA, SP7000 @ £500, improved the link by +5dBm
Adding a more modest LNA (G4DDK @ £55), improved the link by +4dBm
Both the LNAs are high specification units, yet the improvement in link budget is modest. It is conjecture as to how much gain a much simpler LNA added to a typical LoRa module might add.
The full details of the test, how it was done, and the graph of results will be found here;
I will be testing SF12 shortly, and I suspect that since this mode operates much further below noise level than the SF7 used above, the performance improvement will be less.