SimTX API v24/Packets/TxUpdate

TxUpdate

Packet ID	19(0x13)
Direction	Client → server
Session	Transmitter
Body size	1 + 9 × count bytes
Permission	None
Answered by	TxUpdateAck
Answers

TxUpdate changes transmitter settings while the station is on air, without reconnecting. It uses the same field IDs as the TransmitterSessionRequest, restricted to numeric fields. The server answers every TxUpdate with a TxUpdateAck.

Layout

Field	Type	Description
packetId	u8	Always 19.
count	u8	Number of fields, 1–64.
fields	count × { u8 fieldId, i32 length, f32 value }	length must be 4. A field with any other length (up to 1,024) is skipped.

Live fields

ID	Field	Accepted values
5	frequencyHz	1,000 Hz to 3 GHz. Outside: refused.
6	powerWatts	≥ 0. Reduced to at most 1,000,000 W and to the account's tx.pa_limit. Negative: refused.
10	txBandwidthHz	10 Hz to 10 MHz. Outside: refused.
11	audioLowCutHz	≥ 0; values above 5,000 are reduced to 5,000. Negative: refused.
14	finalDriveDb	−40 to 40 (clamped).
15	paHeadroomDb	0.1 to 40.
16	audioCompressionDb	0 to 30.

Any other field ID is refused in the acknowledgement. Changing the modulation, sample rate, source, location or antenna requires a new session.

Rate limits

• If any update was applied less than 250 ms earlier, the whole packet 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.
• At most 16 acknowledgements may be outstanding. A client that keeps sending updates without reading acks is disconnected.

Example

Set power to 50 W and frequency to 7.074 MHz:

13                 packetId 19
02                 count 2
06 00 00 00 04 42 48 00 00      field 6, length 4, 50.0
05 00 00 00 04 4A D7 E1 A0      field 5, length 4, 7074000.0

See also

• Live updates