I’m continuing to perfect the autonomous solar-powered Meshtastic nodes to build a neighborhood mesh network.
I have heard from several sources that the tiny Heltec stubby antennas that come with their LoRa boards are not very good. I am wanting to try alternatives.
There are LoRa antennas on Amazon that make some pretty bold promises (5 dB gain), but I’m sceptical. They also cost $5 or more. Not too bad, you might think, but remember that when this project was conceived the LoRa board itself was only $10 (they’ve since gone up) and the solar spotlight that provides the weatherproof enclosure, solar panel, charging circuitry, and battery is less than $10. Dropping another $5 on the antenna is a bit spendy. After all, if my evil world takeover plan is to come to fruition, I’ll need dozens of these to scatter around my geographically-large neighborhood. Instead, I want to try building my own.
I assembled some 12-gauge solid copper wire from the scrap ends of Romex cable we used to wire the outdoor kitchenette a few days ago, along with an SO239 bulkhead connector ($1.50 each in small quantities.)
I cut the wires and assembled them onto the connector:
- a 78 mm vertical wire
- two 196 mm wires to form the ground-plane radials
Unlike the last antenna I made this way, I used a proper jig to hold it for soldering. It worked great, except that neither of my soldering irons (a simple 25 watt iron I’ve had since I was about 14 and a newer digital iron) produced enough heat — even with great patience — to solder onto the thick metal of the SO connector without leaving crystallized, “cold” joints. These were tools I bought to work on delicate printed circuit boards, not solder on heavy-gauge metal fittings.
Repeater Guy found some cold solder joints on the repeater circuit board which might explain our GMRS mystery, but he doesn’t have an iron small enough to re-flow the solder on the repeater. Like an electronic Jack Sprat rhyme, I’m going to go over tomorrow with my fine, tiny irons and solder the repeater board, and use his big iron to re-flow the solder on my antenna. Together, we’ll lick the platter clean.
Note, however, that mounting the antenna directly to the Heltec board will require a male mini UHF to male UHF adapter. I have a few lying around, but a quick check of Amazon shows that in unit quantities they’re almost as pricey as buying a whole antenna. Sigh.
—2p