A couple months ago my fiber went down - as per Murphy’s Law - on the day of an important work meeting with a partner company. Jamming between the distant AP of my neighbor and my phone hotspot, but both sucked hard. 200ms rtt, 15% packet loss. I was then apologizing profusely while my video started looking like a slideshow from 1998 - and no one could parse what I was saying. Shut down video, keep silent, missed opportunity. Never again!

So I went full paranoid and built a proper 5G backup setup.

The Hardware

• GL.iNet X-3000 with a Quectel RM520N-GL modem
• Poynting XPOL-24 directional antenna mounted on the wall outside my home office

5G signal here is non-existing, so I had to use heavy artillery. The Poynting is a beast. 11 dBi gain, real 4x4 MIMO, cross-polarized, weather-sealed. Point it at the nearest tower and suddenly your SINR jumps from “meh” to “holy shit.”

But pointing a directional antenna without visual feedback is painful. You’re basically spinning in circles, refreshing a web UI, cursing at the sky.

The Software

I wrote a set of tools to solve this: quectel-5g-tools.

5g-info dumps everything your modem knows in a readable format:

5g-monitor is an ncurses TUI that refreshes in real-time and—here’s the good part—beeps based on your SINR. Higher signal quality = more beeps. Point the antenna, listen for beeps, tighten the bolts. Done.

It’s like a metal detector, but for 5G.

Technical Notes

The modem speaks AT commands over /dev/ttyUSB2. The tools parse responses from AT+QENG, AT+QCAINFO, and friends to extract serving cell info, carrier aggregation status, and neighbor cells.

Everything runs on OpenWRT. Install deps with opkg install python3-pyserial python3-toml python3-ncurses, clone the repo, and run ./bin/5g-monitor. No compilation, no containers, no bullshit.

There’s also force-bands if you want to lock your modem to specific LTE/NR bands (useful when the modem insists on connecting to a faraway tower with better RSRP but worse throughput).

Result

My 5G backup now sits at 300+ Mbps down, 50+ up. When fiber dies, my router fails over automatically courtesy of mwan3. Meetings continue. Clients remain unaware. Blood pressure stays normal.

The code is MIT licensed and lives at github.com/vjt/quectel-5g-tools. PRs welcome.

Images

The Poynting right after unboxing and set up on the test tripod:

The X3000 wall-mounted a couple days after the “holy shit!” 300Mbit download moment during testing

The Poynting wall mounted in its (semi) final setup. My biggest DIY so far - I had never drilled concrete before while standing on a 2m ladder on a first floor terrace :-D

Have fun!

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