I have two CubeCell AB01 V2 and tried the pingpong sketch to test the range (16db output power SF12).
I’m in an urban area and I want the signal to go through a building, from my appartment on the second floor to my basement.
Unfortunately my pingpong stops at -111dB after 10-15m in the building, first node on the 2nd floor and the other in the -1 parking.
Signal path is not line of sight but it shouldn’t be blocked much by concrete because first node is at the window and there’s an opening from outside to the -1 basement.
Are the boards / antennas faulty or are my expectations too big for Lora ?
CubeCell AB01 V2 Bad range?
Well, there’s a lot more than just concrete in the average [multi-storey] building. Most likely, the steel reinforcing mesh will be acting like a Faraday cage and your range will be limited accordingly. If you really want to test the range of your boards, you should probably be testing them with an essentially clear line of sight path. Either way, you may get better performance with a [frequency matched] higher gain antenna.
At these frequencies the signal path doesn’t bend. If you are really lucky it may bounce off an intervening building. But UHF is no banana - line of sight means a straight line between one device & another - SLF using vibration of nitrogen & oxygen molecules rather than electromagnetism may yield better results - joking aside, ultrasonics may be worth looking at.
If you can mount a relay outside, forming a triangle that may work. Or just run some very discrete cable or just enamelled wire out your window and then back in to the basement.
It’s not LoRa, it’s the frequency - all modulations will suffer.
What I don’t understand is that when testing using my drone gear (ExpressLRS 868Mhz TX using 100mW LoRa modulation) I can get the signal working through the building even it seems to be very bad (-7dB SNR, -116dB RSSI).
The Cubecell AB01 V2 max output power is 21dBm (~125mW) but unfortunately default is 14dBm (~25mW), is there anyway to increase the max output to 21dBm in EU868 ?
That way, I’m pretty sure I’ll be able to get the signal through.
Yes, but that would be illegal in the EU.
Alternatively, give your ExpressLRS an antenna-ectomy and wire it to the Cubecell?
That’s a great idea but I already tried swapping antennas between ExpressLRS setup and LoRaWAN setup (gateaway + node) but no significant improvement in range 
I’m pretty lost on what to do now, what’s confusing me is that at the beginning I’m pretty sure my range was better than now. Not sure what changed in between, maybe something burned out ?
Both cubecell boards seem to have the same range, I guess it’s unlikely they both burned out. I never powered them without an antenna.
First I’d try reducing the SF by a lot - SF12 is hugely prone to interference due to the long transmission times.
And also look at the structure of the building & try different positions - there may be upright & supporting beams with steel reinforcement but sometimes the floor slabs have less or none if narrow enough - they aren’t supporting the building, just the items on it.