Getting ready for a field test tomorrow, so I decided to see if I can power it with 12 VDC. That would be the easiest solar system to build - one small panel and an AGM or LiFePO4 battery with charge controller - and I can also just jumper it off the batteries in my car or RV. I modified a little POE injector to take 12 volts from my big 30A ham radio supply, and tried to power it up.
Turns out that POE wants 48 V, and that's what the supplied wall wart injector is rated for. That poses some problems. Building a 48 volt solar system is prohibitively expensive - that would be eight GC2 golf cart batteries, and 48 volt solar inverters are expensive. But the docs for the router clearly state that it runs off of 12 to 24 volts. So I was confused.
Luckily, there's a second DC input on the main router board. The 2.1-mm coax jack is labeled "9-24VDC", and when I jumped 12 volts into the jack, the router powered up. Success! I ordered a right-angle coax plug - tight quarters in there - and I'll wire that up to the POE pairs (4,5 + and 7,8 gnd) from the internal RJ45 plug. Sophie suggested soldering them to the coax connector, and maybe that's a good idea. We'll see.
Looks like everything is ready for a field test tomorrow. If I can get it working on site then I'll start tackling the solar aspect - panel, battery, and charge controller. Plus some kind of mounting pole.