I’ll keep this super short and sweet. Keep an eye on this post for updates on antennas as we test them. I’ll do my best to provide a short explanation of the tests, and then a pic of the results. Hope it helps.
What is SWR?
Straight from the wiki: In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave’s amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line. Data found here.
In normal people speak: When a radio transmits, not all the energy exits the antenna. Depending on how well the antenna works, some energy reflects back to the transmitter. Ultimately we want no RF waves/energy being reflected.
Notes: @ 915Mhz SWR 1.29:1 – 30 day stats up. I seem to have a fair few more invalid-witness than compared to a hotspot of equal height/locality using the RAK 5.8dBi
NEBRA Stock 3dBi Antenna
Notes: @ 915Mhz SWR 1.18:1 – Noticeable changes when the antenna is bent at a right angle.
RAK 5.8dBi Antenna
Notes: @ 915Mhz SWR 1.13:1 – Tested a fair bit better than the 8dBi variant. Will be interesting to see how it performs compared to 8 dBi after 30 days.
Who else is testing antennas?
These guys are! – Helium ACT has tested a bunch of antennas including the McGills 6dBi. Will be interesting to see how my results compare. Of note, they mention the right angle of the smaller 3dBi type antennas. I actually ended up with better results when bent to 90deg! Go figure.
Also, if you want to capture some decent historic stats for your setup. Check this website out! https://helium.hiker.rocks/ I used it to make some correlations between invalid witnesses and the type of antenna used.