09 July 2020

LoRA GP antenna

Now that I can map my LoRA signal, I can play with RF and try to get the most out of it. The most straightforward way is to use a better antenna, and probably the only chance to increase range/coverage.

SX1276 with a directly
attached GP antenna.

To keep things simple and straightforward I replaced the helically wound antenna with a ground-plane directly at the SX1276 board. While this is not a real-life situation, it works well for side-by-side comparison. Also I should have tuned the GP to resonance, which requires a connector and/or some coax.

The signal strength as measured by far away TTN gateways is some 7 dB better. If I understand correctly LoRA terms, 7 dB means you can reduce the spread factor by two and achieve the same signal quality. Or quadruple the bandwidth.  And you LoRA experts know the role of SF and BW on airtime vs bps vs whatever_LoRA.

The expert eye should note that the helical antenna was used without an explicit ground plane, so this experiment is probably not meaningful at all. I need to go back to the bench and re-install the coil with the same ground plane.