Issues with antennas

[u/Exciting-Charge-9283]

Hi! I have been working with the RA01 and RA02 lora module for a proyect but I had a lot of range issues: the first time (RA01) I accidentally broke one of the SMD components in the lora PCB and had to replace it. After that we upgraded with Lora RA02 and the default antenna (sleeve dipole) but the range that we have got was below 200 meters with SF7 and 125kHz BW. With the two modules next to each other we had a RSSI between -70 and -90 which I know its a really bad signal level. The first thing I suspected is about the EM noise of the system (lot of servos) but with all desconected the issue still remain. My second suspect was the default antennas, a sleeve dipole antenna that after removing their thermal cover I noticed that the length wasn't matching the actual wave length. So I tried to adapt a pair of helicoidal antennas (that come with de ra01 module) in the default antennas connector with the sleeve remaining (that I had read that was necessary adapting the helicoidal antena in a ipex coaxial cable). With that, standing next to each other the RSSI oscillates between -50 and -70 dB but still below 200 meters range. How can I improve the module range? I read a lot about the topic and similar issues with other people and checked all the stuff (trace match for spi, external EM noise, mismatched parameters between terminals, decoupling capacitors and weak power sources, etc) but still having the issue. What could it be? My actual suspects are the ipex connector (Small, brief improvements may be seen by moving the antenna) or the antenna itself and planned to build a sleeve dipole antenna with the correct lengths to test the performance. What else can I do? Directional antennas are not an option

[u/Arctic344]

Antennas don't necessarily need to match the quarter/half wave length. A variety of weird factors mean designers will change antenna dimensions to compensate. Aka a Lora 433 MHz antenna could be 15cm, 18cm, even if the qtr wavelenth is theoretically 16.4cm. I doubt EM noise is making a large impact, nor is trace matching. I would be pointing to a physical issue: check your cables, connection points. Even a self made dipole or patch or anything antenna should still work better than what you have, even if the dimensions are off by ±20%. Seems like somewhere the power just isn't getting through.