Topband: Digital mode spurious issues

[W2RU - Bud Hippisley]

This is a little off-topic relative to the Subject line, but extremely relevant to enjoyable Topband operating:

On Dec 30, 2013, at 6:51 38PM, Jim Brown <jim at audiosystemsgroup.com> wrote:

> Fast rise time of the keying waveform is the major cause of clicks.  W8JI and others long ago identified this as the cause of the FT1000-series rigs awful clicks, and fixed them. The rise time of some rigs (notably the IC7600) is adjustable, and only the slowest rise time is acceptable. 

Add the venerable Kenwood TS-950SDX to the list of rigs with user-adjustable rise/fall times.  And -- as Jim notes -- only the slowest rise time is fully acceptable, despite the pains Kenwood took to carefully "shape" those RF waveforms during their "on" and "off" transition periods.  

In the case of the 950SDX, the user can select nominal rise/fall times labeled 2, 4, 6, or 8 milliseconds (ms) from one of the configuration menus accessible via the front panel MENU options.  A few years back, in extensive tests on a daytime 80-m band with an equally fanatical friend listening critically, we determined that -only- the 8-ms setting was "clean" with respect to click generation.  Probably the 6-ms setting would be marginally "OK" if the transmitted signal were not loud anywhere, but since my usual objective when chasing DX on 160 is to be as loud as I can, 6 ms is not really an acceptable solution for maintaining good relations with my close-in Topband "neighbors" here on the east coast of North America.  Once we ran those tests, I set the TS-950SDX menu choice to 8 ms, and I've not changed it since.

Bud, W2RU