I have the optional SSB 1.8 filter installed. Soldered it myself and it actually worked after I touched it.
From the owner manual:
TX Filter Bandwidth (SSB/ AM)
Use Menu No. 20 to select one of the following TX filter bandwidths: 2.0 kHz or 2.4 kHz (default).
Display Bandwidth Passband frequency
2.0 2.0 kHz 500 ~ 2500 Hz
2.4 2.4 kHz 300 ~ 2700 Hz
I can also put TX DSP filter as such:
TX Equalizer (SSB/ FM/ AM)
Use Menu No. 19 to change the transmission frequency characteristics of your signal. Uou can select from one of 6 different transmission profiles including the default flat response. Selecting any of the following items from the Menu causes “EQsT”
to appear on the display.
• Off (oFF): The flat frequency response for SSB, FM, and AM (default).
• High boost 1 (Hb1)/ High boost 2 (Hb2): Emphasizes higher audio frequencies; effective
for a bassy voice. High boost 2 does not reduce the low frequency as much as High
• Formant pass (FP): Improves clarity by suppressing audio frequencies outside the formal voice frequency range.
• Bass boost 1 (bb1)/ Bass boost 2 (bb2): Emphasizes lower audio frequencies; effective
for a voice with more high frequency components. Bass boost 2 emphasises more
low frequency response.
• Conventional (c): Emphasizes by 3 dB frequencies at 600 Hz and higher.
• User (U): Reserved for the optional ARCP software.
Off (oFF) is programmed at the factory as a default.