[Elecraft] KX3 digital 0ps?

[Bill Frantz]

There are 3 kinds of digital operation you might want to use: 
wsjt-modes (FT8, FT4 etc.), RTTY, and "Sound card modes" (PSK, 
Olivia etc.). The setup for all of them is similar.

For sound cards (useful in all 3 kinds) a cheap USB "sound card" 
is all you need. I started with a SignaLink years ago, but now I 
have a cheapie I impulse bought from Amazon more recently for 
about $5. The "headphone" output will drive the Mic input of the 
KX3 nicely with a 3.5mm to 3.5mm stereo cable.

For driving the sound card Mic input from the headphone output 
of the KX3, I found I needed a pad to reduce the drive. I have a 
47K resistor in series with the line from the KX3 Phones jack 
and the tip of the plug which goes into the sound card, and a 1K 
resistor between the tip and the sleeve. These resistors fit in 
a 3.5mm plug. The values were based on what I could find in my 
junque box.


For the wsjt-modes, it is best to have CAT control of the radio 
from the computer. For the KX3, the USB to 3.5mm plug used for 
updating the firmware is all the hardware you need. Then wsjt-x 
will set your radio correctly when you select the band in the software.

For RTTY, if you are good with CW and a paddle, you can do the 
whole thing with the KX3. Depending on your computer software, 
you can also treat it like any other sound card mode. Or your 
software can depend on the KX3 encoder/decoder and use CAT 
commands for sending and receiving. Most people doing RTTY from 
a computer like to use the AFSK or FSK modes.


For the other sound card modes, use DATA A, and either use the 
CAT interface to key the radio for transmission, or use VOX on 
the radio.


Getting your computer software connected to these hardware 
interfaces depends on which OS you are using. I use a Mac, which 
just means selecting the correct interface in the setup menus in 
the programs. I have heard complaints from the Windows users 
that software updates make it necessary to redo these 
connections. I haven't tried the Linux world.


Getting the sound levels set correctly is another issue, since 
there are frequently as many as 4 (computer program, OS, sound 
card, and KX3) level controls. On reception, try setting 
everything about the middle of the range, and then aim for the 
highest level that won't overload the A/D converter in your 
sound card. This setting is straight forward in wsjt-x.

For output, again try to set everything to about the middle of 
the range and then set things so the ALC indicator is showing 4 
bars with the 5th one flashing. One gotcha is that when severely 
overdriven, the KX3 will show 0 signal rather than maximum, so 
if you're having problems, start low and work up.

Good luck at Gitmo and maybe we'll see you on the air.

73 Bill AE6JV

On 5/4/20 at 12:21 PM, w1srradio at gmail.com (MIKE W1SRR) wrote:

>so rookie question as I just got my KX3 in time for mobilization (my call
>sign will be KG4MA, wink wink)  I want to setup my KX3 for FT8/FT4/JT9/JT65.
>
>Will have a brand new laptop and of course my radio what all are you using
>for sound cards and settings on the KX3 and WSJT?
>
>If all possible I would like to get a Raspberry Pi computer to lighten the
>load a bit, is that possible?
>
>Thanks in advance
>
>Future KG4MA (in mid june)
>Mike
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