[Moon-Net] TS-2000X SSB TX Output Power Ramping

Paul Andrews w2hro.fn20 at gmail.com
Tue Nov 8 15:53:03 CET 2016

Kenwood has reported that TS-2000X TX Output Power Ramping when using
the ACC2 interface is a real bug / "feature" affecting early models.
My radio is SEPT 2001.  This appears to be a relatively rare bug
unless many operators just haven't seen it because they use the front
panel microphone jack and not the ACC2 interface.

This bug affects only SSB transmissions originated from the ACC2 port.
FM is unaffected.  WSJT transmissions using the front panel Microphone
jack are unaffected.

Kenwood sent me the detailed factory authorized upgrade procedure.   I
have the procedure document in PDF form and will provide it to anyone
who asks.  Is there a good place that this procedure could be posted
for all interested to review?

The fix is not trivial.  The easy part is removing 1 resistor and
adding another.  Removing and replacing a 150 pin SMD IC chip is a
little more complicated and then the final step is a full upgrade of
CPU and DSP firmware.  At the end of the procedure Kenwood writes,
"when complete - no adjustments are needed".  :)

It appears that this TX power ramping is written into the DSP.
Kenwood could have offered this as an option.  The idea of "soft
start" for audio digital modes is interesting.  This "soft start"
could be easily written into WSJT and could minimize the TX power
overshoot problem that SSPA owners worry about.

I have decided (like others) that this 2 second TX power ramp is
actually a very valuable "FEATURE" because it helps treats solid state
amps kindly by avoiding the abrupt 0 to 100% output transition or
overshoot spikes.   Hey - I'm making lemonade out of lemons.   I have
not tested to see if this TX Power ramp exists on 70cm or 23cm.  I'll
be testing soon.

Thanks for all your responses to my original question.  In summary, 2
moon net readers knew this was a TS-2000 bug and had experience with
it.  10 others had not experience this issue.

73 - Paul - W2HRO

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