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POCSAG Receiver
Eisenberger Tamas edited this page 2024-01-22 11:49:50 +01:00
Receives pager messages using the POCSAG protocol.
This protocol operates in the VHF/UHF bands using FSK modulation. More technical details can be found by following the links in the References section.
UI Overview
Settings
- Frequency: Sets the frequency to receive pager messages on. Can be adjusted with the encoder thumb wheel, on-screen numpad, or loaded from frequencies saved on an SD card. 439.9875 MHz is the most popular worldwide frequency used by Amateur radio for POCSAG. Amateur radio POCSAG uses 1200bps.
- RF amplifier (0 or 1): Enables/disables the internal RF amplifier.
- LNA gain (0, 8, 16, 24, 32, 40): Sets the LNA gain. Further information: Description of the gain settings
- VGA gain (0 to 62): Sets the VGA gain. Further information: Description of the gain settings
- RSSI/Audio: Top bar indicates signal strength. Bottom bar indicates the audio level. The audio bar can be useful for tuning settings without headphones/speaker to hear the tone.
- Squelch (0-99): Sets the signal to noise threshold. 0 disables squelch. Higher values allow more noise. Should be set so that strong signals are clearly received without any dropped audio.
- Volume: Output volume for the received audio. Can be used to monitor received signal quality.
Information
- Decoder Status: Indicates the status of the decoder state machine. White: Idle, Cyan: Clear, Yellow: Waiting for message start, Green: Waiting for rest of message.
- Batch Count: Number of message batches that have been received. A batch has 16 codewords.
- Bits: Displays the bits that are being decoded into codewords.
- Sync: Green when the frame decoder has received a "sync" frame. Messages are not decoded unless a sync frame is found.
- Codewords: Shows the number of codewords in the current batch. When the bar fills, the batch is complete and is processed.
- Baud Rate: The detected rate of the current message. 05: 512bps, 12: 1200bps, 24: 2400bps.
Buttons
- Ignore Last: Enables "Ignore" mode for the last received address.
- Config: Enters the settings page to configure options.
Config
- Enable Log: Logs messages to the SD Card at "LOGS/POCSAG.TXT"
- Log Raw Data: Logs the batch codewords as hexadecimal. Useful for debugging decoder bugs.
- Use Small Font: Uses the 5x8 font in the UI to show more messages on the screen.
- Hide Bad Data: Don't show (or log) codewords that fails checksum validation.
- Hide Addr Only: Don't show (or log) codewords that don't contain a message.
- Enable Ignored Address: Don't show (or log) codewords sent to the specified address.
- Beta: Enable the new POCSAG baseband processor. The app must be restarted for this to take effect.
- Save: Save any settings changes.
NOTE: App Settings must be enabled for settings to be saved.
Message Display
Typical message:
12:34 1200 #432123 F2
This is a test message
Description (from top-left):
12:34- Time: The time that the message was received (time from PortaPack).1200- Data rate: The data rate used to receive the message.#432123- Address: The address of the intended pager recipient.F2- Function: (0 to 3) Indicates the type or source of message sent (can be used to provide a category of sorts).This is a test message- Message: The message data displayed as ASCII.
References
The following resources provide more technical information about the POCSAG protocol:
- POCSAG - Signal Identification Wiki - Provides frequencies commonly used in different countries and regions
- POCSAG - WikiPedia