[Elecraft] HF Digital interface for the K2...

[Don Wilhelm]

Ken and all,

I no longer have kits, but I have 18 boards available.  The output of the
fixed audio board is isolated from all other signals in the K2, so
connection to the board output will not have any effect on any normal
function of the K2.  If you want a look, go to my website
http://w3fpr.qrpradio.com.  I do have an updated method to mount the board
between the front panel and the control board which is ideal for those who
want to use no connectors and/or want the output signal to connect to the
mic jack - the resistors and capacitors are laid down flat or low profile
components may be used.

The input to the audio amp on my board is close to the equivalent of the
signals appearing at J5 - I just chose to use the outbound side of the mute
transistors rather than the direct product detector output - for some reason
at the time, I wanted my fixed audio muted, and the connections were easier
doing it the way I did.

There is no problem with using the output from J5 as suggested by MicroHam,
except that it is a very low level, and the MicroHam interface has no
amplifier - it simply feeds the balanced output through their box and on to
the soundcard connected as a single ended signal - so they lose 3 dB by
switching to single ended output and depend on the soundcard gain to
compensate - it will work, but could reduce the signal to noise ratio at the
soundcard input.

I suppose I will get a rash of requests for the board now <G>.  When these
18 are gone, they will be no more, but the circuit is easy to wire on a
piece of perfboard, and I am considering an update to provide the K2 with
both input and output for digital modes so you can plug directly to the
computer soundcard (no interfece box required), but I do need to find the
time to put something together.

73,
Don W3FPR

> -----Original Message-----

>
> I have Don's fixed audio mod in my K2 and it works
> very well.  It's wired to the front panel mic
> connector, which works perfectly when you use the
> Tigertronics SL-1+ audio interface.
>
> I spoke to Don about MicroHam's using the audio
> available from J5 inside the K2.  He didn't think it
> was a good idea, but he can explain why better than I
> can.
>
> 73,
>
> Ken Alexander, VE3HLS
>
>
> --- Tom Hammond <n0ss at earthlink.net> wrote:
>
> > Don Wilhelm, W3FPR, offers a really nice fixed
> > output interface for the K2.
> >
> > However, it may NOT offer output of the CW SIDETONE,
> > since that comes
> > in on a different input port to the AF amp and is
> > not currently
> > sampled by the fixed output amp.
> >
> > Contact Don at:  Don Wilhelm W3FPR <w3fpr at arrl.net>
> >
> > 73,
> >
> > Tom Hammond   N0SS
> >
> >
> > At 11:18 AM 3/10/2007, Peter wrote:
> > >Hi
> > >
> > >A small audio amp. and you have fixed audio level
> > at the back.
> > >
> > >http://www.pi4cc.nl/personal/pc2a/k2/
> > >
> > >Peter
> > >PC2A
> > >
> > >Tony Lyon schreef:
> > >>Jamie,
> > >>Thanks.... Being able to connect to the J5
> > connector looks like it
> > >>will do the trick. I looked
> > >>in the K2 manual and I noticed that the J5 AF
> > output is derived
> > >>directly  from pins 4 and 5
> > >>of the NE602 product detector.
> > >>
> > >>So, my next question is:.
> > >>Does the NE602  have enough output drive to drive
> > the AF input of a
> > >>RigEXpert?
> > >>
> > >>73,
> > >>Tony Lyon (KJ5XF)

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