[Elecraft] K3 on JT-65, ALC varies widely

[Joe Subich, W4TV]

 > I set the LINE IN gain to 30 (midrange).

This is generally too high - I run between 10 and 15.

> The speaker output is set to 90%,

Are you running the "bare" speaker output to the Line In or
do you have a 10:1 (20 dB) attenuator between the speaker
output and the Line Input?

> but there is an amplitude slider in WSJT-X, and I adjusted that to 5
> bars of ALC in WSJT Tune mode (constant 1100 Hz tone in this case).

This is the *WORST PLACE* to adjust the level.  Set the WSJT-X slider
to max and make an attenuator with a 10K resistor from the speaker out
to the top of a 1 K pot and connect the wiper of the port to Line IN.
Adjust drive with the pot.

> On an external analog wattmeter, I could see the power ramping up on
> some of the longer duration tones.

This is a symptom of insufficient audio drive and/or failure to
properly perform Transmitter Gain CAL (in the K3 Utility).

 > So then I took an oscilloscope and measured the audio voltage coming
 > out of the sound card, and found that each tone has a different
 > voltage level coming out of the sound card!  The audio level varies
 > all over the place as the CQ goes on.

Contact the WJTS-X development team - their list is:
     wsjtgroup at yahoogroups.com


73,

    ... Joe, W4TV


On 4/17/2017 1:43 PM, Dave Hachadorian wrote:
> I am working on this some more this morning.
>
> I set the LINE IN gain to 30 (midrange).  The speaker output is set
> to 90%, but there is an amplitude slider in WSJT-X, and I adjusted
> that to 5 bars of ALC in WSJT Tune mode (constant 1100 Hz tone in
> this case).  The K3 is definitely in DATA A mode.
>
> Then I called CQ, and the ALC meter and power output were all over
> the place from 0 - 5 on ALC, and 10 Watts to 70 Watts on power
> output.  On an external analog wattmeter, I could see the power
> ramping up on some of the longer duration tones.
>
> So then I took an oscilloscope and measured the audio voltage coming
> out of the sound card, and found that each tone has a different
> voltage level coming out of the sound card!  The audio level varies
> all over the place as the CQ goes on.  JT-65 is supposed to be
> constant amplitude tones of 65 different frequencies, so something is
> not working right, either in the WSJT-X program or in my computer.  I
> will look into that some more.  It is not a K3 problem.
>
> I am using WSJT-X v. 1.7.0 r7405.  The sound card is an old
> Soundblaster Live that works just fine for transmitting WAV and live
> microphone on SSB.
>
> Anyway, I am making QSO’s, some of them with signal strength as low
> as –25 dB.  I don’t think I am long for this mode anyway.  Life is
> too short for 1 Baud communication.
>
> Dave Hachadorian, K6LL Yuma, Arizona
>
>
>
>
>
>
>
> -----Original Message----- From: Don Wilhelm Sent: Sunday, April 16,
> 2017 7:41 PM To: Brian Hunt ; Reflector Elecraft Subject: Re:
> [Elecraft] K3 on JT-65, ALC varies widely
>
> Brian,
>
> Try this -- set the K3 LINE in gain to somewhere near mid-range, and
>  then adjust the soundcard "speaker" slider to give you close to the
> 4 ALC bars with the 5th bar flashing.  Refine that level with slight
>  adjustments to the LINE in gain.
>
> You can use TX TEST while making those adjustments which will not
> transmit any RF.
>
> Adjust the desired power output with the power knob.
>
> If you do not achieve the required number of ALC bars, the K3 will
> "power hunt" causing significant fluctuations in the output power.
>
> There seems to be a greater number of questions about this "problem"
> for users of "JT" software than for other soundcard data modes.  I
> don't know why because the "JT" software should be no different than
> any other soundcard data mode.  Perhaps the user is trying to follow
> the recommendations in the JT mode instructions (I have not looked at
> them), but typically data mode instructions are for non-Elecraft
> tranceivers and say that the user should set the power to maximum and
> use the soundcard audio to adjust the power level.  That does not
> work with Elecraft gear which controls power differently than other
> amateur transceivers.  For Elecraft transceivers, adjust the audio
> level as specified and adjust the desired power with the power knob.
> I cannot stress this fact enough.
>
> 73, Don W3FPR
>
> On 4/16/2017 9:19 PM, Brian Hunt wrote:
>> Don't see a problem with making minor adjustments of the Line In
>> gain during the first transmission. When I adjust the level using
>> the WSJT TUNE button I usually see the wild fluctuations mentioned.
>> A small "tweak" to the gain will set right.
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