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

[Dave Hachadorian]

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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