Locked Re: FST4 modes with TS-890S - slow RF envelope rise problem #txaudio

Peter Hall, VK6HP


If you'll permit me to comment, it's not a matter of revising the software to work with one design.  LF/MF users, where the FST4 modes are targeted, very often use highly efficient, non-linear amplifiers (such as Class D or E) with the prevailing digital and CW modes.  Within these common designs the proper place to control RF envelope shaping is in the amplifier, not the exciter and, indeed, the usual topologies cannot reflect any exciter waveform shaping in their outputs.  Furthermore, not only is exciter waveform shaping wasted, it's counterproductive in a spectral containment sense if it leads to some amplifiers emitting spurious transients.

While I strongly suspect the present heavy envelope shaping can be reduced to keep everyone happy (as they are with WSPR, JT9, ...), another simple solution is to have the option to allow LF/MF users to retain or disable shaping, catering to both linear PA users and the large body of non-linear amplifier users.  In the end, there's no point making life difficult for a large fraction of the target user base, especially if the ambition is to have the FST4 modes replace the earlier modes.

73, Peter.

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