I’ve been doing some unscientific testing of commerical antennas and built a cheap wire collinear. I picked up a Diamond SRH229 dual band (222/33CM) handheld antenna and NR920 mobile collinear. Compared to the stock antennas I found an increase of about 6 miles, compared to about 2 miles using the stock T-Beam antennas. However the inital T-Beam test was with one radio sitting on the kitchen counter and the other on the car dash, while the NR920 was mounted in the attic, about 8 ft higher and the SRH229 on a SMA mag mount on top of my vehicle. This was all using the default settings (US channel 0, Long Fast modulation).
Inspired by the result I thought I’d try my hand at building a collinear for the attic. At the hardware store I found some long bamboo poles used for training tomato plants, etc in the garden, grabbed some old wire and a N barrel. I used the spreadsheet developed by Leonard, Wb3AYW. I just used the default measurements on the spreadsheet which worked out to about 10 turns for each trap. I also used an old N Male to SMA male jumper and a split toroidal core to better match the transmitter. If I read my VNA correctly I was pretty close to the center frequency of 908 MHz without further tuning. So I repeated the test drive, and had the same results, even with some snow and rain. Total cost was about $12 but all from my parts box.
One thing that didn’t change no matter what, I live near a natural gas injection well. Many of these wells use 900 MHz radios for telemetry and remote control. The well is about a mile from my home and has a panel antenna pointed back to the company office, with my house in-between. This seems to interefere enough to create a pretty solid dead zone in that direction, so that no messages are acknowledged. No combination of antennas has made any difference. Also noticed that standing next to a bank of smart power meters stopped transmission but going across the street worked just fine. The nice thing about having that dead zone has made it easy to test placing a third radio in a good location to “prove” the mesh is working as designed.
The final thought is that I’m really impressed with the battery life on the T-Beam radios. I’ve charged the “rover” radios once since I began testing and they’re still at 85% after about 3 hours use with GPS active. I think there’s real potential for Meshtastic to be a really useful tool for outdoors use. I bought a few Gotenna devices but the limitations on the devices were pretty obvious, the lack of an API, external antennas or iGate capability. Meshtastic fixes all these issues and opens up possiblities like APRS gateways and sensor networks. I hope it gets some traction.