Editing Advanced Transmitter Settings

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Fifteen parameters define a transmitter's imperfections. In the SimTX desktop app they are set in two places:
* '''On a station's radio.''' Each radio stores all fifteen under '''Transmitter imperfections''' in the station editor. Choosing a model under '''Based on''' fills them. See [[SimTX Guide/Stations#Radios|Radios]].
* '''For one transmission.''' In the '''Transmit''' tab, '''Transmitter imperfections''' in the '''RF signal''' section adjusts four of them: Final drive, Compressor, Freq error and AM index. They start from the station radio's values. The other eleven come from the radio.

== Which setting to change ==
Start from a [[Radio Presets|radio model]] and change one value at a time while listening to your own transmission.
{| class="wikitable"
! Problem !! Settings
|-
| Distorted audio || The source's '''Audio gain''' first, then Final drive, Compressor and PA headroom.
|-
| Signal off the dial frequency || Freq error.
|-
| An imperfect radio on purpose || Hum, noise, leakage and the mode-specific settings.
|}

PA means power amplifier. Headroom is the margin before it saturates. Carrier leak, sideband suppression, hum level, TX noise and phase noise are in decibels below the wanted signal: a larger number means a cleaner transmitter.

== Parameter reference ==
{| class="wikitable mw-collapsible mw-collapsed"
! Setting !! Default !! Range !! Effect
|-
| Final drive (dB) || 0.0 || -40 to 40 || Extra drive into the power amplifier. Positive values push the amplifier toward compression and distortion.
|-
| PA headroom (dB) || 12.0 || 0.1 to 40 || How far below amplifier saturation the nominal signal sits. Small headroom means the signal clips early.
|-
| Compressor (dB) || 1.5 || 0 to 30 || Audio compression before modulation. Raises average loudness at the cost of naturalness.
|-
| PA softness || 2.8 || 0.5 to 10 || Shape of the amplifier limiting curve. Low values clip abruptly (harsh distortion), high values limit gently.
|-
| AM/PM (deg) || 6.0 || 0 to 45 || Phase shift that accompanies amplitude compression. Adds splatter and roughness when the amplifier is driven hard.
|-
| Carrier leak (dB) || 60.0 || 0 to 120 || Suppression of the residual carrier in suppressed-carrier modes. Higher is cleaner.
|-
| Sideband sup. (dB) || 60.0 || 0 to 120 || Suppression of the unwanted sideband in SSB. Higher is cleaner.
|-
| Freq error (Hz) || 0.0 || -10000 to 10000 || Static frequency offset of the transmitter oscillator.
|-
| Hum level (dB) || 120.0 || 0 to 120 || Mains hum suppression; 120 means no audible hum. Lower values add hum at the hum frequency.
|-
| Hum freq (Hz) || 0.0 || 0 to 400 || Mains hum fundamental (typically 50 or 100, or 60 or 120). Zero disables.
|-
| AM index || 0.85 || 0 to 1.2 || AM modulation depth. Above 1.0 is overmodulation with distortion and splatter.
|-
| PA sag (dB) || 0.0 || 0 to 30 || Supply voltage sag under load; produces a power dip on voice peaks and key-down.
|-
| TX noise (dB) || 120.0 || 0 to 160 || Broadband transmitted noise floor suppression. Higher is cleaner.
|-
| Phase noise (dB) || 120.0 || 0 to 160 || Oscillator phase noise suppression. Higher is cleaner; low values smear the signal spectrally.
|-
| CW rise (ms) || 5.0 || 0 to 50 || CW keying envelope rise time. Very short values cause key clicks.
|}

[[Category:SimTX]]