[Elecraft] KX3 buzz if power up on transverter band

[Drew Arnett]

Elecraft reported that they were able to reproduce the problem before
the end of October.

Haven't heard anything more, yet.

On Sat, Sep 12, 2020 at 3:51 PM Drew Arnett <arnett.drew at gmail.com> wrote:
>
> Anybody have a chance to try this?  Would be useful to know if someone
> else cannot.  Would be equally useful to know if someone can.  Still
> waiting to hear back from Elecraft.
>
> Thanks,
>
> Drew
> n7da
>
> On Fri, Aug 21, 2020 at 3:22 PM Drew Arnett <arnett.drew at gmail.com> wrote:
> >
> > Oscilloscope "screenshot" of the offending waveform:
> >
> > https://drive.google.com/drive/folders/1-g9Met098lhncAcMtAAOvxWFDjf0NU_w?usp=sharing
> >
> > Can anyone try to reproduce this to rule out or confirm my suspicion
> > it might be caused by firmware bug?
> >
> > You can imagine how fast I knocked my headphones off!  :-O  :-)
> >
> > Thanks and best regards,
> >
> > Drew
> > n7da
> >
> > On Wed, Aug 19, 2020 at 2:49 PM Drew Arnett <arnett.drew at gmail.com> wrote:
> > >
> > > Hi,
> > >
> > > Weird problem.  Anyone else try this and do or don't see this?
> > >
> > > Just got my KX3 back from repair.  This included an upgrade to the
> > > latest firmware.  (Makes sense.  Requirement for production test.  I
> > > hadn't upgraded to the very latest, because I had no need for the
> > > latest improvements.)
> > >
> > > Set the radio back up for 10368 to 50 MHz transverter use on XVTR1
> > > band.  Now, if I power up the radio when it was shut down on the XVTR
> > > band, there is a crazy loud buzz on the audio output (and
> > > corresponding response of the S meter.)  If I switch to any other
> > > non-XVTR band and then power up, no problem even if switching then to
> > > the XVTR band.
> > >
> > > FW is now 2.90/1.52I got the radio back just before the 10 GHz
> > > contest, so only made minimal changes to settings from the cleared
> > > state it came back in.  Changes made:
> > > AFX mode off (was delay)
> > > ATU bypass (can't remember if it came back this way or not.  XVTR is
> > > good 50 ohm load.)
> > > BAT CHG off (was not inst)
> > > BKLIGHT off (was on)
> > > MIC BIAS off (I think came back on; used dynamic mic during contest)
> > > MIC BTN Ptt (was up/down)
> > > TX DLY 10 (was 5.  abundance of caution as 5 is more than enough for
> > > the 10 GHz rig I'm running)
> > > XV1 on
> > > XV1 RF 10368
> > > XV1 IF 50
> > > XV1 PWR 0.1
> > > XV1 OFS (set in field) 1.20
> > > XV1 ADR trn1
> > > set the clock.  :-)
> > > turned on the hidden in the menus CW-in-SSB feature
> > >
> > > I know I turned on or off a couple of front panel things as they left
> > > it.  Don't remember.  Stuff like vox, pre, nr or nb.  Definitely
> > > adjusted mic gain and compression and keyer speed.  :-)
> > >
> > > RX ISO changed to on during the contest, but problem occurs with it on or off
> > >
> > > What does the headphone jack output look like?  Power up in bad state.
> > > Set volume control to 20.  With no load other than 10X scope probe,
> > > the AC component is identical for left and right.  Tip has about 0 V
> > > DC offset.  Ring has about + 0.5 V DC offset.  AC component looks like
> > > a the differential of a square wave.  Peak to peak amplitude is 220
> > > mV.  (This follows volume control.  Didn't check to see if DC offset
> > > follows volume control.)  12.2 millisecond repetition rate for
> > > positive and negative pulses.  Negative pulse leads positive pulse by
> > > 2.2 ms, so 10 ms from positive pulse to negative.  Very small AC
> > > ripple on that with a period of about 0.4 ms.
> > >
> > > I was very happy to find a sequence to avoid the problem (as described
> > > above.)  To trouble shoot, I tried to rule out a number of things.
> > > Unplugged ALL cables from the KX3.  That did not resolve.  Tried
> > > external 12.4 V (battery on hand) and internal battery removed.  Tried
> > > internal battery (charged) and nothing plugged in.  No dice.
> > >
> > > Given that it's just back from repair, that sequencing gets it in a
> > > bad state, FW was upgraded to a new version, and audio path goes
> > > through FW, seems reasonable to ask if this is a known FW issue or if
> > > someone can try to reproduce this.
> > >
> > > Hoping to figure this out before the Sept VHF, the Sept 10 GHz contest
> > > weekend, and of course the HF contests coming up later this fall.  :-)
> > >  With my workaround, I was able to participate in the Aug 10 GHz
> > > weekend without interruption.  I ran a W1GHZ XVTR barefoot (+5 dBm
> > > Pout) for best DX of 379 km.  How much fun can you have with a KX3?
> > > Lots!  :-)
> > >
> > > Thanks and best regards,
> > >
> > > Drew
> > > n7da