You bound your ExpressLRS receiver and everything flies fine — but your EdgeTX radio shows zero sensors, and the telemetry screen is blank. ELRS sends a rich telemetry stream by default, but your radio won’t display it until you change one setting that’s buried two menus deep. The fix takes 30 seconds, and once you know where it lives, you won’t make the mistake again.
The Critical Setting: Receiver → Telem Ratio
ELRS transmits telemetry in the same packets as the RC link — it’s not a separate radio. The ratio of telemetry to RC data is controlled by the Telem Ratio setting, and here’s where most people get stuck:
In the ExpressLRS Lua script (on your radio):
1. Long-press the SYS button, navigate to the ExpressLRS folder, launch elrsV3.lua
2. Scroll down to Receiver section
3. Find Telem Ratio — this is set on the RECEIVER side of the link, not the transmitter module
4. Set it to 1:4 or 1:2. The default is often 1:16 or 1:32, which sends one telemetry packet for every 16 or 32 RC packets. At 500Hz packet rate, 1:16 gives you ~31 telemetry samples per second — enough for slowly-changing data like GPS and battery voltage. For fast-changing data like current sensors, use 1:4 or 1:2.
5. Telem Ratio alone controls whether telemetry flows. If you’re seeing zero sensors, this is set too high (1:64 or 1:128, or Std telemetry mode is selected) or your radio isn’t running the sensor-discovery step.
Alternative: Std vs. Full Res telemetry. Some ELRS firmware builds offer “Std” (standard) vs “Full Res” telemetry modes. Std mode sends only RSSI and link quality. Full Res sends everything — GPS, battery, current, attitude, flight mode. If you flashed your receiver with a Std firmware build, re-flash with the Full Res version. Check your receiver’s firmware target: if it says _ELRS without _FULL, you’re on Std. Flash targets include _ELRS_FULL suffix.
Run Sensor Discovery on EdgeTX
After setting Telem Ratio and rebooting both the receiver and transmitter module, EdgeTX needs to discover the sensors:
- Press MDL button → scroll to Telemetry page
- Select Discover new sensors
- Wait 10-15 seconds. The radio polls the CRSF stream and populates the sensor list.
- You should see: RSSI, RxBt (receiver battery), 1RSS (RSSI dBm), RQly (link quality), RFMD (RF mode), TPWR (transmit power), plus any sensors the flight controller forwards through CRSF.
If discovery finds nothing: (a) verify the quad is powered on and armed (some flight controllers only forward telemetry when armed), (b) check that CRSF telemetry is enabled in Betaflight Receiver tab (Telemetry output = CRSF), (c) confirm Telem Ratio isn’t 0 or “off.”
CRSF Telemetry: What ELRS Actually Sends
ELRS packs telemetry into the CRSF protocol, which EdgeTX parses natively. The sensor IDs are standardized:
| Sensor ID | Label | Unit | Description | Minimum Refresh Rate |
|---|---|---|---|---|
| 0x01 | 1RSS | dBm | RSSI in decibel-milliwatts (negative) | Every packet |
| 0x02 | RQly | % | Link quality (100% = zero packet loss) | Every packet |
| 0x03 | RSNR | dB | Signal-to-noise ratio | Every packet |
| 0x04 | RFMD | — | RF mode (0=4Hz, 1=25Hz, 2=50Hz, 3=100Hz, etc.) | On mode change |
| 0x05 | TPWR | mW | Current transmit power | On power change |
| 0x06 | TRSS | dBm | Transmitter-side RSSI (how well TX hears RX) | Every packet |
| 0x07 | TQly | % | Transmitter link quality | Every packet |
Flight controller data (GPS, battery, altitude, heading, flight mode) is forwarded through the CRSF passthrough. The flight controller injects these as CRSF sensor frames, and EdgeTX discovers them as additional sensors. If your GPS coordinates aren’t showing on the radio but GPS lock is confirmed in Betaflight OSD, check that CRSF telemetry passthrough is enabled: Betaflight → Receiver tab → “Telemetry” = “CRSF.”
OSD Telemetry Widgets (Hardware vs Software)
EdgeTX radios with color screens (TX16S MKII, Boxer Crush, Zorro Max) can display telemetry widgets on the main screen. Configure them in the Telemetry page → Widget settings:
- Top Bar: RSSI bar graph (slot 1), Link Quality percentage (slot 2)
- Main Screen (full-width widget): GPS coordinates + satellite count (for long range), Battery voltage + current + mAh consumed
Black-and-white screen radios (Radiomaster Pocket, Jumper T-Lite) can still set telemetry callouts — have the radio speak “RSSI low” at your chosen threshold. In the Special Functions page, create:
– SF1: ON, Play Value, 1RSS, repeat 10s (reads RSSI dBm every 10 seconds)
– SF2: ON, Play Value, RQly, repeat 15s (reads link quality)
Telemetry Logging and Review
EdgeTX logs all telemetry sensors to the SD card by default. The log file is in LOGS/ with the model name and date. After a range-test session:
- Power off the radio, eject SD card, open the log in a CSV viewer
- Plot 1RSS (RSSI dBm) over time against GPS distance
- The cliff where 1RSS drops from -95 to -105 dBm in a single second is your practical range limit for that location
- RQly stays at 100% until the very edge — when RQly drops below 90%, you’re within 100 meters of failsafe
This data is more actionable than RSSI percentage alone. RSSI percentages are scaled non-linearly for display convenience; dBm is the raw RF measurement.
Common Mistakes & How to Avoid Them
Mistake 1: Not power-cycling after changing Telem Ratio. ELRS applies the ratio change on next boot, not mid-flight. After changing the ratio in the Lua script, power-cycle both the receiver (unplug quad LiPo) and transmitter module (use the Lua “Reboot TX” option or power-cycle the radio).
Mistake 2: Sensor discovery with the quad disarmed. Some Betaflight builds suppress telemetry forwarding until the quad is armed. The sensor discovery will complete but find only the basic ELRS sensors (1RSS, RQly, TPWR) — no GPS, no battery voltage, no flight mode. Arm on the bench (props off), run sensor discovery again, and you’ll see the full sensor set.
Mistake 3: Confusing 1RSS with RSSI. 1RSS is the raw dBm value (negative number, -30 to -110). RSSI is the scaled 0-100% display value. If your logical switch uses RSSI for a low-signal warning, the threshold of “20” means 20% — sensible. If you accidentally bind the switch to 1RSS with threshold “20,” it will trigger at -20 dBm — which never happens, so the warning never fires. Verify which sensor your logical switches reference.
Mistake 4: Running Telem Ratio 1:2 at 1000Hz. At 1000Hz packet rate with 1:2 telemetry ratio, the receiver tries to send 500 telemetry packets per second. That consumes significant receiver CPU time and radio bandwidth, and the actual data (GPS coordinates, voltage) only updates at 10-20Hz from the flight controller anyway. 1:4 or 1:8 at 500Hz is plenty — you’re not missing data, you’re just burning link budget on empty packets.
⚠️ Regulatory Notice: The flight recommendations in this article should be followed in accordance with the latest 2026 drone regulations in your country or region. Always verify local laws regarding flight altitude, no-fly zones, remote ID requirements, and registration before flying. Regulations vary significantly between the FAA (US), EASA (EU), CAA (UK), CAAC (China), and other authorities.
ELRS telemetry gives you link quality data that feeds directly into your RSSI OSD setup. We covered the relationship between RSSI dBm, link quality, and what to display in your goggles in our RSSI setup guide.
The telemetry sensors ELRS exposes are the same ones EdgeTX uses for logical switches and special functions. We covered programming logical switches and audio callouts extensively in our EdgeTX programming guide.
A radio that parses CRSF telemetry natively makes sensor setup a one-click affair. The Radiomaster Boxer Crush with internal ELRS module discovers all sensors automatically on bind and displays them on the color touchscreen without any Lua script navigation — the fastest path from binding to full telemetry.