Epson scanner on 5 GHz: it needs a 20 MHz channel
Our Epson RapidReceipt RR-620W scanned fast, then took a minute to show the pages. It was stuck on a bad 2.4 GHz link. The spec sheet says it has a 5 GHz radio, but it would not join 5 GHz at all until one access point ran a 20 MHz channel. Then it scanned cleanly, for one afternoon. By evening it would not hold the link, and it is back on 2.4 GHz. We could not find any of this written down anywhere, so here it is, including the part that did not last.
The symptom
The scanner pulls a stack of receipts through in seconds. Then Epson ScanSmart on the Mac sits there and the page previews trickle in. Some days it could not find the scanner at all.
It looked like a Mac problem, since it started around a macOS upgrade. It was not. The scanner buffers the pages and sends them over Wi-Fi afterward, and that transfer was the slow part.
What the network showed
We pinged the scanner once a second while a scan ran. On its 2.4 GHz link the replies went from 10 ms to several seconds, and one ping in four was lost. The access point's counters told the same story. It had to send most frames to the scanner two or three times, and it had dropped its data rate to the scanner to 2 Mbps, the lowest it has. Every other device on that radio was fine.
| During a scan | 2.4 GHz | 5 GHz, 20 MHz |
|---|---|---|
| Average ping reply | 910 ms | 8 ms |
| Worst ping reply | 4.0 s | 25 ms |
| Lost pings | 117 of 480 | 0 of 232 |
| Data moved | 22 MB | 23 MB |
The scanner only receives tiny acknowledgements during a scan, so a weak downlink should not matter much. It does. TCP slows down when the acknowledgements are late, and the pages crawl.
Why it stayed on 2.4 GHz
Epson's spec sheet lists the radio as 802.11a/b/g/n/ac. So we tried to move it. In order:
- Kicked it off Wi-Fi so it would pick again. It came back on 2.4 GHz.
- Moved the nearest access point's 5 GHz radio off a DFS channel, from 52 to 36. No change.
- Turned on band steering, "prefer 5 GHz," on that access point. No change.
- Made a 5 GHz-only Wi-Fi name with the same password. The scanner listed it, took the password, and failed to connect. A phone joined it fine.
- Set the 5 GHz radios to 40 MHz. Still failed.
- Set them to 20 MHz. The scanner joined inside a minute.
We then went back to 40 MHz to be sure. The scanner dropped and would not rejoin. Back to 20, and it was on again in forty seconds. So this scanner needs a 20 MHz channel on 5 GHz, full stop. DFS channels are fine; it ended up on channel 132.
It was not distance. A Ring camera on the same 80 MHz radio was holding a link at -76 dBm the whole time, while the scanner, at -61 dBm, could not join.
The setup that keeps everyone else fast
This is the setup we built. Read the update further down before you copy it: it worked for one afternoon and then stopped.
Channel width is set per radio in UniFi, not per Wi-Fi name. If you set 20 MHz everywhere, your laptops lose most of their speed. So give the scanner one radio.
- Settings > WiFi > Create New. A 5 GHz-only network,
WPA2, on your normal LAN or your IoT VLAN. We called ours
iot_5g. - In that Wi-Fi's settings, under Broadcasting APs, create a new group that holds only the access point closest to the scanner, and pick it. Now the name exists on that one AP.
- Devices > that access point > Radios > 5 GHz: channel width 20 MHz. Leave your other access points at 80.
- On the scanner: Settings > Network Settings > Wi-Fi Setup, pick the new name, type the password.
If the 20 MHz access point also carries your main Wi-Fi name, move that name to an AP group without it, so phones and laptops never land on the narrow radio. Our scanner joined at -61 dBm and reported 86 Mbps. The whole scan transfer takes about four seconds now.
One honest detail: even on 5 GHz, the access point still has to send most frames to this scanner more than once. The narrow channel does not make the scanner's receiver good. It makes a weak receiver workable, because a 20 MHz channel packs the same power into a quarter of the bandwidth.
Things that bit us
- Every Wi-Fi or radio change in UniFi re-provisions the access points, and every wireless client blinks for about thirty seconds. Batch your changes. We did them one at a time and bounced the whole house four times in an hour.
- The scanner does not always rejoin Wi-Fi after one of those blinks. Twice it sat offline until we reselected the network on its screen. Check it after any change.
- The scanner's Power Off Timer took it off the network entirely until someone pressed the power button. That looked like a Wi-Fi fault too. We set it to none and left the sleep timer alone. Sleep only dims the screen and costs about a watt.
- Band steering and a DFS-free channel changed nothing. Width was the whole problem.
- The scanner's web page, at its IP address over HTTPS, shows the band, channel, and signal it sees under Network Status. The login name is blank and the default password is the serial number. Change it.
Update, the same evening
Three hours after that clean scan, the scanner started dropping the 5 GHz link on its own: connected for one to twelve minutes, then gone, over and over, with the channel nearly idle and the access point reading it at -59 dBm. Its own screen said the signal was poor. We turned off UniFi's IoT optimization and 802.11v on that network, tried channel 165 and went back to 132, turned band steering off on every access point, and power cycled the scanner. After the restart it would not join 5 GHz at all. It joined 2.4 GHz at once.
So the honest result is this. We got the scanner working on 5 GHz with a 20 MHz channel, for a short time. It did not last. The radio hears the access point far worse than the access point hears it, on both bands, and even on 2.4 GHz it needs most frames sent twice. It is back on 2.4 GHz, slow but connected, and the 5 GHz network comes out tomorrow.
What we believe, and this is our opinion, not something we can prove from outside the case: the Wi-Fi radio in this unit is not good enough for 5 GHz and has trouble even on 2.4 GHz. Epson sells it as a wireless scanner, but the radio is not built to the standard of the rest of a modern home network, let alone an office one. Our guess is a cheap commodity Wi-Fi module. The scanning hardware is fine. The radio lets it down.
Would we buy it again?
No. The scanner itself is good: fast, duplex, and the receipt software does what it says. The Wi-Fi is the problem. It would not use its 5 GHz radio until one access point gave up most of its speed for it, and then would not keep that link. It does not reliably rejoin after the network changes, and its own power-off timer took it offline for days. A home network should not have to be rebuilt around one device.
If you buy one anyway, or already own one, plan on the USB cable. It ships in the box, the scanner has a USB 3.0 port, and a wired link skips every problem on this page. We have not run ours that way yet, so we cannot say how much faster it is, only that the Wi-Fi was the slow part of every scan we measured.
Is this documented anywhere?
Not that we could find. Epson's troubleshooting pages say a scanner may fail to join if the access point uses an "unsupported channel," and suggest separate names for the 2.4 and 5 GHz bands. They do not mention channel width. Forum threads about older Epson printers suggest 20 MHz, but for 2.4 GHz. If you have the same scanner and a different result, or an Epson page that says this, we would like to know.
Sources
- Epson RR-620W specification sheet (PDF), the 802.11a/b/g/n/ac line
- Epson: scanner cannot connect to a wireless router
- Epson ES-580W: Power Off and Sleep Timer settings, the same menus as the RR-620W