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Documentation of the Franklin R910 for use as a secondary WAN link

Franklin R910 Device Specifications:

  • Battery Life: 12 hrs usage / 27 hrs standby
  • Number of Connected Devices: 10 Wi-Fi
  • LTE Bands: 25, 26, 41 (aka "Sprint Spark") - hardware also supports 2, 4, 5, 12
  • LTE-Advanced Carrier Aggregation
  • LTE Performance Category 4 (Max Theoretical Speed: 150Mbps Down / 50Mbps Up)
  • Wi-Fi Technology / Frequencies: 802.11 b/g/n - 2.4GHz , 802.11ac - 5GHz
  • Dimensions: 3.46" x 2.62" x 0.47" / 3.5 oz

Antenna Notes:

  • Oficially no antenna jacks.
  • R910 has small black stickers covering 6 TS9 female connectors.
  • These are around the perimeter of the device, not under the battery or label. device diagram
  • the plastic surround of the device contains small antennas that are connected to pads next to these ports.device diagram
  • removing that plastic surround shows ports that are labeled in pairs: 1708 MAIN, 1708 DIV, B41 MAIN, B41 DIV ports image
  • B41 ports do not appear to improve signal for operation where I am, since band 41 signal appears weak. These appear to be dedicated to band 41 since that uses very different frequencies and modes.
  • WARNING: connecting to the B41 connections seems to put the device into an unstable state where it will then not reconnect to any network without a hard reset.
  • Plugging an antenna into 1708 MAIN and 1708 DIV pairs does increase the signal (RSSI and RSRQ) on both bands 25 and 26.
  • You can view which band is in use and signal values at Debug Engineering Hidden Page and the MSL isn't needed to access this page.
  • To make connections with the TS9 straight barrel connectors I have, I needed to drill out plastic surrounds with 1/4 inch drill.
  • Placing a $20 panel antenna on an old satelite dish and directing this at the tower increase signal strength and speed. dish mount
  • Using the satellite dish limits the bands that are used because this is really useful only in the 2 GHz range.

Tethering Notes:

  • Set the USB mode for tethering under USB mode in the webpst hidden page and change to mode "RNDIS + DIAG + ADB [Android]"
  • Access to this requires use of the MSL for the device.
  • This particular mode makes it look like a phone for tethering versus a dumb modem or usb stick.
  • I connected the device to a super cheap GL.iNet mini router and configure it for tethering
  • This tiny device runs openwrt and has some useful modules installed.
  • Go to advanced settings in the GL.iNet and add the eth0 WAN port to the WAN interface so that usb and eth0 are bridged together
  • Connect the upstream router to the GL.iNet WAN port and configure it to do DHCP
  • This will get an IP from the r910 directly versus double NAT.
  • Then MultiWAN can be configured on the main router.
  • using another mode the setting name is "internet" and the APN is "r.ispsn"

Frequencies:

  • Sprint uses LTE bands 25, 26, and 41.
  • the modem is configured to use these in that prioritized order.
  • the modem also supports 2, 4, 5, and 12.
  • wikipedia has a listing of LTE bands
E-UTRA band Duplex mode ƒ(MHz) Common name Included in (subset of) band Uplink (UL) Downlink (DL) Duplex spacing Channel bandwidths
2 FDD 1900 PCS blocks A–F 25 1850 – 1910 1930 – 1990 80 1.4, 3, 5, 10, 15, 20
4 FDD 1700 AWS blocks A–F (AWS-1) 66 1710 – 1755 2110 – 2155 400 1.4, 3, 5, 10, 15, 20
5 FDD 850 CLR 26 824 – 849 869 – 894 45 1.4, 3, 5, 10
25 FDD 1900 Extended PCS blocks A–G 1850 – 1915 1930 – 1995 80 1.4, 3, 5, 10, 15, 20
26 FDD 850 Extended CLR 814 – 849 859 – 894 45 1.4, 3, 5, 10, 15
41 TDD 2500 BRS / EBS 2496 – 2690 N/A 5, 10, 15, 20

Sources:

Guide to Antenna Connectors

Common RF Connectors

FCC frequency info on the R910

R910 User Guide

reddit page on the R910

Where to see LTE details on the R910

Where to change USB mode for tethering

using a old sat dish as a relector

CRC9 versus TS9

Sprint R910 Page

RV Mobile Internet Review of R910