[Elecraft] MFJ 1279 and K2

[W3FPR - Don Wilhelm]

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
>