Quick Answer
Why is my RTK base station not sending corrections?
The most common causes of RTK base station correction failure are: the base receiver is not configured to broadcast (survey not started or base mode not active), UHF radio is on the wrong frequency or the antenna is not connected, cellular NTRIP credentials are incorrect or the mount point is not active, the receiver battery is dead, or a cable between the receiver and radio module is damaged. Work through these in order — most base station problems are found within the first two checks.
How to Troubleshoot an RTK Base Station Not Sending Corrections
Applies to: Trimble R10/R12 Base, Topcon HiPer HR/VR Base, Leica GS18 Base, Spectra SP80 Base; UHF radio and cellular correction broadcast
An RTK base station that stops sending corrections takes the entire survey crew off production. Every rover working off that base goes from Fixed to Float and can't do precise stakeout or data collection. Most base station correction failures are simple configuration or hardware issues that a crew member can diagnose and fix in 5-10 minutes. This guide walks through the systematic diagnostic process from quickest checks to deeper investigation.
Step 1: Confirm the Base Survey Is Active
The most common field error: the base receiver is powered on and tracking satellites, but the base survey routine was never started in the controller software, or the base stopped broadcasting because the controller disconnected from the receiver. Reconnect the field controller to the base receiver via Bluetooth and check the survey status screen.
In Trimble Access, navigate to Survey > Current Survey. Confirm the base is in active base mode (not stopped or paused). In Topcon Magnet Field, check Survey > Base Mode status. If the base survey has stopped, restart it — re-enter the control point coordinates, antenna height, and correction format, then restart broadcasting. Rovers should re-acquire Fixed within 60-90 seconds of corrections resuming.
Step 2: Check the Radio or Cellular Link
For UHF radio broadcast: Look at the base radio unit. The transmit LED should flash at the configured broadcast interval (every 1 second typically). A transmit LED that is dark or steady (not flashing) indicates the radio is not transmitting. Check:
- Radio antenna connection: the antenna cable from the receiver to the radio whip. A loose or disconnected antenna is the most common radio problem.
- Radio frequency: confirm the base radio frequency matches the rover radio frequency. Even 1 channel off prevents communication.
- Radio power: confirm the radio module is powered (indicator LED lit) and that the cable connecting it to the receiver is secure.
- Correction protocol: verify base and rover are set to the same protocol (CMR+, RTCM 3.2, or RTCM 2.3).
For cellular NTRIP broadcast: Check the receiver's cellular signal strength indicator. No signal means no corrections. In an area with cell coverage, check:
- NTRIP caster connection status in the receiver's web interface or controller software
- Mount point name — confirm it was created on the caster and is active
- Login credentials — confirm username and password are entered correctly
- Data plan — confirm the SIM card's data plan is active
Step 3: Check the Receiver Power and Battery
A receiver that appears on but is actually running on critically low battery may stop transmitting corrections while still displaying the screen. Check the battery indicator on the receiver's built-in display or in the controller battery status screen. If battery is below 20%, connect external power. RTK base sessions typically run 6-8 hours on internal battery — plan for a battery swap on long days or connect to an external 12V supply.
For receivers powered via vehicle 12V: check the power cable and fuse. Field vehicles have rough environments and power cable connections loosen. A receiver that powers on and off intermittently usually has a loose power connection.
Step 4: Check Satellite Count and PDOP
If the base receiver has fewer than 5 tracked satellites, it may suspend correction broadcast or reduce broadcast quality. Causes of low satellite count at the base: tree canopy growth, temporary obstructions (parked vehicles or equipment adjacent to the tripod), or satellite constellation gaps at certain times of day.
Check the satellite count display on the base receiver. Move obstructions away from the receiver and re-orient the base antenna if possible. Sky obstructions that block more than 25% of the sky hemisphere significantly affect performance. Waiting 15 minutes for the satellite geometry to change sometimes resolves low-count windows.
Step 5: Verify Rover Configuration
If the base appears to be broadcasting correctly but rovers are still not receiving, the issue may be on the rover side. Check:
- Rover radio frequency matches base frequency
- Rover is configured to receive corrections (not set to autonomous or NTRIP when using UHF)
- Rover is within radio range of the base
- Rover antenna is connected and not damaged
Test with a second rover if available — if one rover connects and another does not, the issue is isolated to the failing rover's hardware or configuration.
Frequently Asked Questions
How do I tell if my RTK base is transmitting corrections?
The UHF radio transmit LED flashes at the broadcast interval (typically 1 per second) when transmitting. In the controller software, the base status screen shows "broadcasting" or an active correction count. Some receivers also show a transmission count in the status screen that increments with each broadcast.
What does it mean when a rover shows Float instead of Fixed?
Float means the rover is receiving some correction signal but has not resolved carrier phase ambiguities to Fixed status. Possible causes: correction signal too weak, correction protocol mismatch, base just started broadcasting (initialization takes 30-90 seconds), or PDOP is too high. Float that persists beyond 5 minutes with correction signal present usually indicates a protocol mismatch or base configuration problem.
Can a base station be set up on the wrong coordinates and still transmit corrections?
Yes — the base will transmit corrections that are mathematically valid but position-shifted. Rovers will achieve RTK Fixed status but all stakeout will be consistently offset by the coordinate error. This is the most damaging type of base station error because it appears correct. Always verify rover position against a known independent control point before beginning layout.
How far can an RTK base station radio reach?
Typical UHF radio range is 5-10 km in open terrain with the base antenna elevated. Range is significantly reduced in valleys, near large metal structures, or with the base antenna low to the ground. If work areas are beyond reliable radio range, consider adding a radio repeater or switching to cellular NTRIP corrections.
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