Editing SimTX API v24/Packets/TxTelemetry

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{{SimTX packet v24
| name = TxTelemetry
| id = 7
| hex = 0x07
| direction = s2c
| session = [[SimTX API v24/Transmitter session|Transmitter]]
| size = 81 bytes
| permission = None
| group = transmitter
}}
'''TxTelemetry''' reports the state of a transmitter while it is on air: power at each point of the chain, standing-wave ratio, amplifier compression and temperature, and the server's playout buffer. The server sends it about every 50 ms from [[SimTX API v24/Packets/TxAccept|TxAccept]] until the session ends. These are the values behind the meters of the official transmitter.

== Layout ==
{| class="wikitable"
! Field !! Type !! Description
|-
| <code>packetId</code> || <code>u8</code> || Always <code>7</code>.
|-
| <code>sequence</code> || <code>i64</code> || Increments with each telemetry packet.
|-
| <code>serverTimeMillis</code> || <code>i64</code> || Server wall-clock time, Unix milliseconds.
|-
| <code>actualFrequencyHz</code> || <code>f32</code> || Frequency on air, including any frequency offset.
|-
| <code>requestedPowerWatts</code> || <code>f32</code> || Power requested, after the account limit.
|-
| <code>forwardPowerWatts</code> || <code>f32</code> || Power leaving the amplifier toward the antenna.
|-
| <code>deliveredPowerWatts</code> || <code>f32</code> || Power actually accepted by the antenna.
|-
| <code>reflectedPowerWatts</code> || <code>f32</code> || Power reflected back by the mismatch.
|-
| <code>vswr</code> || <code>f32</code> || Voltage standing-wave ratio at the feed point.
|-
| <code>mismatchLossDb</code> || <code>f32</code> || Loss due to the mismatch, in dB.
|-
| <code>transformerLossDb</code> || <code>f32</code> || Loss in the matching transformer, in dB.
|-
| <code>foldbackLossDb</code> || <code>f32</code> || Power reduction by SWR protection, in dB.
|-
| <code>alcDb</code> || <code>f32</code> || Automatic level control reduction, in dB.
|-
| <code>bufferSeconds</code> || <code>f32</code> || Samples waiting in the server's playout buffer, in seconds.
|-
| <code>finalsTemperatureC</code> || <code>f32</code> || Temperature of the final amplifier, °C.
|-
| <code>thermalFoldbackDb</code> || <code>f32</code> || Power reduction by thermal protection, in dB.
|-
| <code>paCompressionDb</code> || <code>f32</code> || Amplifier gain compression, in dB.
|-
| <code>paHeatWatts</code> || <code>f32</code> || Heat dissipated in the amplifier, in watts.
|-
| <code>paEfficiencyPercent</code> || <code>f32</code> || Amplifier efficiency, percent.
|-
| <code>paThermalFaultActive</code> || <code>bool</code> || True while the amplifier is in thermal fault.
|}

== Usage ==
* '''Pacing:''' <code>bufferSeconds</code> is the most useful field for a streaming client. It should stay above zero (otherwise listeners hear gaps) and below about two seconds (otherwise latency grows and input may be discarded).
* '''Antenna match:''' a high <code>vswr</code> with large <code>reflectedPowerWatts</code> and <code>foldbackLossDb</code> means the antenna is not resonant on the frequency. See [[SWR and Transmitter Protection]].
* '''Heat:''' <code>finalsTemperatureC</code>, <code>thermalFoldbackDb</code> and <code>paThermalFaultActive</code> follow the amplifier model described in [[Power Amplifier Behaviour]].
* Telemetry is coalesced. A slow reader gets the most recent values rather than a backlog; <code>sequence</code> may skip.
* The client must keep reading. A client that does not read for 5 seconds is disconnected.

In Python: <code>struct.unpack(">qq16f?", body)</code>.

== See also ==
* [[SWR and Transmitter Protection]]
* [[Power Amplifier Behaviour]]

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