SimTX API/Packets/TxUpdate

TxUpdate

Frame	ClientFrame, field 14
Member	tx_update
Direction	Client → server
Session	Transmitter
Roles	ROLE_TX_AUDIO, ROLE_TX_GENERATED, after TxAccept.
Permission	None
Answered by	TxUpdateAck
Answers
Defined in	session.proto

TxUpdate changes transmitter settings while the station is on air, without reconnecting. Every field except request_id is optional; send only the fields that change. The server answers each TxUpdate with a TxUpdateAck.

Definition

message TxUpdate {
  int64 request_id = 1;
  optional double frequency_hz = 2;
  optional float power_watts = 3;
  optional float bandwidth_hz = 4;
  optional float audio_low_cut_hz = 5;
  optional float final_drive_db = 6;
  optional float pa_headroom_db = 7;
  optional float audio_compression_db = 8;
  optional float audio_gain = 9;
}

Fields

#	Field	Type	Description
1	request_id	int64	Chosen by the client; echoed in the TxUpdateAck. Use a new value for each update.
2	frequency_hz	optional double	Live field FREQUENCY. 1,000 Hz to 3 GHz; at most one frequency change per second.
3	power_watts	optional float	Live field POWER. ≥ 0; reduced to at most 1,000,000 W and to the PA cap.
4	bandwidth_hz	optional float	Live field BANDWIDTH. 10 Hz to 10 MHz.
5	audio_low_cut_hz	optional float	Live field LOW_CUT. ≥ 0; values above 5,000 Hz are reduced to 5,000 Hz.
6	final_drive_db	optional float	Live field FINAL_DRIVE. Clamped to −40 to 40.
7	pa_headroom_db	optional float	Live field PA_HEADROOM. Clamped to 0 to 40.
8	audio_compression_db	optional float	Live field AUDIO_COMPRESSION. Clamped to 0 to 40.
9	audio_gain	optional float	Live field AUDIO_GAIN. Clamped to 0 to 100.

Rate limits

• If any update was applied less than 250 ms earlier, every field of the update is refused.
• A frequency change is refused if the previous frequency change was less than 1 second earlier.
• Refused fields are reported in the ack with accepted = false. They are not queued; send them again later.
• Changing the modulation, sample rate, source, site or antenna needs a new session. Antenna pointing changes use AntennaPointingUpdate.

Examples

Complete frames, including the varint length prefix.

tx_update (client to server, 19 bytes):

12                            frame length 18
72 10                         tx_update (TxUpdate), 16 bytes
  08 07                       request_id = 7
  11 00 00 00 20 A6 E9 5A 41  frequency_hz = 7055000.5
  1D 00 00 48 42              power_watts = 50

tx_update_audio_gain (client to server, 10 bytes):

09                frame length 9
72 07             tx_update (TxUpdate), 7 bytes
  08 08           request_id = 8
  4D 00 00 40 3F  audio_gain = 0.75

See also

• Live updates
• TxUpdateAck