Title: Transmitting Signals
Description: Replay captured SubGHz signals to control devices
URL: /v2.1/subghz/transmitting/
Version: v2.1
Section: SubGHz
Search index: /search-index.json

# Transmitting Signals

> Replay captured SubGHz signals to control devices

## On this page

- [Before you start](#before-you-start)
- [Transmitting a saved signal](#transmitting-a-saved-signal)
- [On-device UI](#on-device-ui)
- [Command line](#command-line)
- [Frequency matching](#frequency-matching)
- [Protocol considerations](#protocol-considerations)
- [Decoded signals](#decoded-signals)
- [Raw signals](#raw-signals)
- [Tips for successful transmission](#tips-for-successful-transmission)
- [Notes](#notes)
- [Troubleshooting](#troubleshooting)

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Replay captured signals to control garage doors, gates, alarms, and other SubGHz devices.
## Before you start
- Hardware: Board with CC1101 SubGHz support (see [Hardware Support](/v2.1/subghz/hardware/)).
- Captured signals: Saved .sub files in /mnt/ghostesp/subghz/ (see [Capturing](/v2.1/subghz/capturing/)).
- Frequency matching: Ensure the transmission frequency matches the target device’s expected frequency.
## Transmitting a saved signal
### On-device UI
- Open SubGHz → Saved to browse captured signals.
- Select a .sub file from the list.
- Review the signal details (protocol, frequency, code).
- Choose Replay to transmit the signal.
- The device will transmit on the frequency stored in the file.
### Command line
# List all saved signals
subghz list
# Load and replay a specific signal (load and replay are aliases — only call one)
subghz load <name>
# Load the last captured signal
subghz load last
## Frequency matching
Signals are transmitted at the frequency stored in the .sub file. If the target device expects a different frequency:
- Edit the .sub file to change the Frequency field (see [Files](/v2.1/subghz/files/)).
- Or use the [Frequency Analyzer](/v2.1/subghz/freq-analyzer/) to determine the correct frequency before capturing.
## Protocol considerations
### Decoded signals
For signals with decoded protocols (Princeton, CAME, KeeLoq, etc.):
- GhostESP reconstructs the signal from the decoded code and protocol parameters.
- Transmission should be reliable if the protocol was correctly identified.
- Some protocols use rolling codes; replay may fail if the target device expects a new code.
### Raw signals
For raw captures (unknown protocol):
- GhostESP transmits the exact timing sequence that was captured.
- Ensure the capture was clean and complete for reliable replay.
- Raw signals are more sensitive to timing and environmental factors.
## Tips for successful transmission
- Distance: Start within 5-10 meters of the target device.
- Antenna orientation: Point the antenna toward the target receiver.
- Multiple attempts: Some devices require multiple transmissions to respond.
- Interference: Avoid areas with strong RF interference.
- Frequency verification: Use the Frequency Analyzer to confirm the target device’s frequency.
## Notes
- Transmission power is limited by regulatory requirements and hardware capabilities.
- Some devices use rolling codes or challenge-response mechanisms that prevent simple replay attacks.
- Commercial security systems may have additional protections against replay attacks.
- Always ensure you have authorization to control the target device.
## Troubleshooting
- No response from device: Verify the frequency matches the target device. Check antenna connection and orientation.
- Transmission fails: Ensure the .sub file is valid and not corrupted. Try recapturing the signal.
- Intermittent success: The device may use rolling codes or require specific timing. Try multiple transmissions.
- Wrong frequency: Edit the .sub file to correct the frequency, or recapture on the correct band.