MFJ 1279 and K2

[James T. "Jim" Rogers, W4ATK]

I will pass this along for what it is worth.
        First a bit of background.
        a) The MFJ breaks the audio path from the sound card to the mic unless PTT
is activated. This is a good thing.
        b) The MFJ provides an optically isolated CW keying circuit. This too is a
good thing.
        c) The K2's ptt and dot line are one in the same. This has caused some
consternation for those who would like to use, of all things, a footswitch
(and I have a circuit that remedies that if anyone should need it. I don't).
With the MFJ then there exist two paths for CW keying, the optically
isolated path and simply keying PTT on the mic connector of the K2 via the
MFJ.

Why this was a problem for me:
        I did not like to hear the relay chattering away when on CW and felt it was
advantageous not to have sound card audio routed to the K2 during cw keying.
It did not produce a problem, I just did not like it.

My solution:
        I installed a spst toggle switch of the miniature variety just above the
"Footswitch" jack on the MFJ and hard wired the switch to JMP5. NO to
JMP5-3, C to JMP5-2, NC to JMP5-1, I placed labels on the front panel
labeled "K" for keying and "P" for PTT. Now I do not hear the relay when I
am in CW mode with MixW and with a simple flip of the switch when I change
modes to PSK31 the MFJ PTT circuitry is activated and audio from the sound
card is routed to the radio. Cool.

        I have also programmed PF2 to go directly to the INP menu for selecting
Padl keying or Hand keying (for the confuser) and PF1 to go directly to the
PA menu for turning the amp on/off. And I made a "y" cable for the CW out of
the MFJ that ties the CW out from the MFJ to the dot side of the paddle. A
switch here a press there and voila' It works for me!

73 Jim, W4ATK
K2/100 #4028

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[Don Wilhelm-3]

Jim and all,

If you are interested in a different (and perhaps more convenient) method of
adding a 'real' PTT to the K2, check out the article on that subject on my
website www.qsl.net/w3fpr.

73,
Don W3FPR

----- Original Message -----

>I will pass this along for what it is worth.
> First a bit of background.
> a) The MFJ breaks the audio path from the sound card to the mic unless PTT
> is activated. This is a good thing.
> b) The MFJ provides an optically isolated CW keying circuit. This too is a
> good thing.
> c) The K2's ptt and dot line are one in the same. This has caused some
> consternation for those who would like to use, of all things, a footswitch
> (and I have a circuit that remedies that if anyone should need it. I
> don't).
> With the MFJ then there exist two paths for CW keying, the optically
> isolated path and simply keying PTT on the mic connector of the K2 via the
> MFJ.
>
> Why this was a problem for me:
> I did not like to hear the relay chattering away when on CW and felt it
> was
> advantageous not to have sound card audio routed to the K2 during cw
> keying.
> It did not produce a problem, I just did not like it.
>
> My solution:
> I installed a spst toggle switch of the miniature variety just above the
> "Footswitch" jack on the MFJ and hard wired the switch to JMP5. NO to
> JMP5-3, C to JMP5-2, NC to JMP5-1, I placed labels on the front panel
> labeled "K" for keying and "P" for PTT. Now I do not hear the relay when I
> am in CW mode with MixW and with a simple flip of the switch when I change
> modes to PSK31 the MFJ PTT circuitry is activated and audio from the sound
> card is routed to the radio. Cool.
>
> I have also programmed PF2 to go directly to the INP menu for selecting
> Padl keying or Hand keying (for the confuser) and PF1 to go directly to
> the
> PA menu for turning the amp on/off. And I made a "y" cable for the CW out
> of
> the MFJ that ties the CW out from the MFJ to the dot side of the paddle. A
> switch here a press there and voila' It works for me!
>
> 73 Jim, W4ATK
> K2/100 #4028
>

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