Is your TRB500 5G connection unstable? You're not alone.
The Teltonika TRB500 ships with Quectel RG501Q-EU modem firmware A08, which has serious 5G stability issues:
| Symptom | Description |
|---|---|
| 5G drops constantly | Connects to 5G-NSA, then drops back to LTE after 10-20 seconds |
| High latency spikes | Ping jumps from 20ms to 500ms+ during 5G↔LTE handovers |
| Poor signal metrics | SINR stuck at 5-7 dB even with good antenna placement |
| Unstable speeds | Connection speed fluctuates wildly |
The Web UI says "Modem updates from server not supported" - but the firmware IS available, Teltonika just doesn't expose it through the UI.
This guide shows you how to manually update to modem firmware A11, which:
- Fixes 5G-NSA stability (connection stays up)
- Improves SINR dramatically (5-7 dB → 15-18 dB)
- Includes the "5Ghoul" security patch
- Delivers stable ~100 Mbit/s speeds on 5G
- Teltonika TRB500 with SSH access enabled
- Root password or SSH key authentication configured
- Stable internet connection (LTE is fine)
# Router firmware
ssh root@192.168.1.1 'cat /etc/version'
# Modem firmware
ssh root@192.168.1.1 'gsmctl -A "AT+QGMR"'Example output for A08:
RG501QEUAAR12A08M4G_04.200.00.000
Download latest firmware from: https://wiki.teltonika-networks.com/view/TRB500_Firmware_Downloads
Update via Web UI:
- Access http://192.168.1.1
- Navigate to: System → Firmware → Update Firmware
- Upload the .bin file
- Check "Keep settings"
- Click Update and wait ~5 minutes
The full A11 firmware is available on Teltonika's servers (81 MB):
# Download to /overlay (has more space than /tmp)
ssh root@192.168.1.1 'cd /overlay && curl -o modem_a11.tar "https://modemfota.teltonika-networks.com/TRB5/RG501QEUAAR12A11M4G_04.200.04.200"'Verify download:
ssh root@192.168.1.1 'ls -lh /overlay/modem_a11.tar'
# Should show ~81 MBssh root@192.168.1.1 'modem_upgrade --check --file /overlay/modem_a11.tar'Expected output:
Image validated successfully
WARNING: Do not interrupt this process. Do not power off the router.
ssh root@192.168.1.1 'modem_upgrade --file /overlay/modem_a11.tar'This takes approximately 2 minutes. You'll see output like:
Validating image...
Extracting firmware...
Flashing partition 1...
Flashing partition 2...
...
Firmware update complete
ssh root@192.168.1.1 'reboot'Wait 2-3 minutes for the router to fully boot.
ssh root@192.168.1.1 'gsmctl -A "AT+QGMR"'Should now show:
RG501QEUAAR12A11M4G_04.200.00.000
After the firmware update, the modem may be in airplane mode. Enable radio and 5G:
# Enable radio
ssh root@192.168.1.1 'gsmctl -A "AT+CFUN=1"'
# Enable 5G-NSA mode
ssh root@192.168.1.1 'gsmctl -A "AT+QNWPREFCFG=\"nr5g_disable_mode\",0"'
ssh root@192.168.1.1 'gsmctl -A "AT+QNWPREFCFG=\"mode_pref\",NR5G:LTE"'
# Restart mobile interface
ssh root@192.168.1.1 'ifdown mob1s1a1 && sleep 3 && ifup mob1s1a1'ssh root@192.168.1.1 'gsmctl -t && gsmctl -q'Expected output:
5G-NSA
RSSI: -61
RSRP: -88
SINR: 16
RSRQ: -9
The AT command settings don't survive reboots. Create a startup script:
ssh root@192.168.1.1 'cat > /etc/rc.local << "EOF"
#!/bin/sh
# Wait for modem to initialize after boot
sleep 30
# Enable radio (exit airplane mode)
gsmctl -A "AT+CFUN=1"
# Enable 5G
gsmctl -A "AT+QNWPREFCFG=\"nr5g_disable_mode\",0"
gsmctl -A "AT+QNWPREFCFG=\"mode_pref\",NR5G:LTE"
# Wait and restart mobile interface to establish connection
sleep 10
ifdown mob1s1a1
sleep 3
ifup mob1s1a1
exit 0
EOF
chmod +x /etc/rc.local'To make the Web UI show the correct network mode:
ssh root@192.168.1.1 'uci set simcard.@sim[0].service="nr5g_pref" && uci commit simcard'Remove the firmware file to free up space:
ssh root@192.168.1.1 'rm /overlay/modem_a11.tar'ssh root@192.168.1.1 'gsmctl -t'
# Output: 5G-NSAssh root@192.168.1.1 'gsmctl -q'ssh root@192.168.1.1 'gsmctl -A "AT+QCAINFO"'ssh root@192.168.1.1 'gsmctl -A "AT+QENG=\"servingcell\""'# Note: Shows -140 dBm when idle. Run during download to see all antennas:
ssh root@192.168.1.1 'curl -o /dev/null http://speedtest.tele2.net/1MB.zip 2>/dev/null & sleep 1 && gsmctl -A "AT+QRSRP"'| Metric | Before (A08) | After (A11) |
|---|---|---|
| 5G Stability | Drops after 10-20s | Stays connected |
| SINR | 5-7 dB | 15-18 dB |
| RSRP | -94 dBm | -88 dBm |
| Speed | Unstable | ~100 Mbit/s |
ssh root@192.168.1.1 'gsmctl -A "AT+CFUN=1"'ssh root@192.168.1.1 'ifdown mob1s1a1 && sleep 3 && ifup mob1s1a1'Use /overlay instead of /tmp - it has more available space.
The RG501Q-EU modem doesn't support DFOTA (delta updates). Use the full firmware method described above.
This is a network/SIM issue. Contact your carrier to enable 5G SA on your account.
After a modem firmware update, the modem's NVM (non-volatile memory) is reset. The 5G mode settings (AT+QNWPREFCFG) need to be re-applied after each boot.
5G-NSA uses LTE as an "anchor" connection. The 5G NR layer is added dynamically when:
- There's high data demand (downloads, streaming)
- Cell load permits
- Signal quality is sufficient
When idle, you may see LTE-only - this is normal.
The TRB500 has 4 SMA connectors for 4x4 MIMO. All antennas are wideband (LTE + 5G). The modem powers down unused RX chains when idle to save power.
| Resource | URL |
|---|---|
| Full A11 firmware | https://modemfota.teltonika-networks.com/TRB5/RG501QEUAAR12A11M4G_04.200.04.200 |
| Firmware list | https://modemfota.teltonika-networks.com/TRB5/fwlist.txt |
| Router firmware | https://wiki.teltonika-networks.com/view/TRB500_Firmware_Downloads |
Guide created: 2025-12-21 Tested on: TRB500 with Router Firmware 07.20, Modem A08 → A11