[Elecraft] K2 On the Way -- Planning for Mods?

[Tom Hammond NØSS]

Bill

AA4LR wrote:

> >Definitely the xtal grounding mod!
>
>OK. I think you offered some chip caps for this mod as well, no?

Actually, I recommended nothing.

The original idea for the mod came from KO0V (if I recall), and subsequent 
to that, KI6WX did a much more detailed write-up on the mod, and produced a 
PDF of it.

There was a suggestion of adding chip caps, however, if memory serves, it 
was also mentioned that any improvement due to the addition of the chip 
caps was minimal and probably not worth the added effort/cost.

> >Consider adding the CW Sidetone mod as well... it makes a fairly
> >significant improvement in what you're gonna hear for hours on end while
> >contesting.
>
>I hadn't heard about this one.

This one comes courtesy of Randy Hargenrader, WJ4P.

   From: "Randy Hargenrader" <randyh@harksystems.com>
   To: <elecraft@qth.net>
   Subject: [Elecraft] SINEWAVE SIDETONE
   Date: Sat, 26 Feb 2000 02:26:53 -0500
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   K2'ers,

   Tonite I finally cracked the sidetone "nut"! I now have a pure
   sinewave from the sidetone circuit working in serial numbers
   183 and 661. It's VERY easy. Here's the modification to the
   control board...

   1) Add a 47 K ohm resistor to the position of C24, a .0027uF
      capacitor. Pull up one side of C24. It doesn't matter which
      side. I had to completely remove it first then extend one
      lead out from the body of the capacitor so that it would
      have one lead in a hole and one lead up in the air for a
      "flying connection". Add the 47K ohm resistor to the other
      hole, also standing on end. Tack solder the top of the 47K
      ohm resistor to the "top" lead of C24, making a "flying"
      connection. Note: If the only modification you make is to
      add the 47K resistor, the tone will smooth out enough that
      you WILL notice a difference (for the better) but the tone
      will not be a clean sine wave. The next step will give the
      sine wave.

   2) Make sure C33 is a 2.2uF electrolytic capacitor. (If you
      made the previous modifications to the sidetone I suggested
      some time ago, you might want to use these new values.)
      Solder a 47mH inductor across pins 7 and 10 of RP5. Do not
      remove RP5, and there is no need to cut any traces. Just
      tack solder the 47mH inductor across pins 7 and 10 of RP5.
      Note: For those of you who prefer to run low frequency
      sidetones, the sidetone begins to become slightly distorted
      below 530Hz and loses the nice sinewave shape below that. To
      compensate, use a 4.7uF cap at C33 or tack a 2.2uF cap
      across it on the back of the board. The higher frequency
      side-tones will be nice but at a slightly lower amplitude
      which isnt really a problem since you can reset the level at
      will.

   Your done! Put your K2 back together and start enjoying the
   sweet sound of a sine wave sidetone!

   BTW, miniature 47mH chokes are available from Mouser
   Electronics - part number: 434-03-473J, at 800 346 6873.
   Approximate cost $1.36 each. Usual disclaimers...

   72, Randy WJ4P

> >As a preventive measure, e.g. easier to do now than later, add the AF GAIN
> >MOD.
>
>I remember reading about this one. However, I thought Elecraft found the
>problem and would have incorporated the change into recent K2 kits. I
>just ordered my kit last week, so wouldn't it have this fix?

Could be, but I suspect it'll see the light of day inn the next iteration 
of the RF board, which is only about to hit Wayne's drawing board. Until 
that time, I'd plan on installing it myself.

> >Finally, be sure to install the VFO "Walk" mod.
>
>That was just discussed recently. I didn't realise there was a mod for
>this as well.

Wayne posted it a couple weeks ago. I wrote it up for them, and it's now on 
Eric's PC (somewhere) awaiting it appearance on the Elecraft Web Site.

>You have URLs for these? I'll download them and put them in my file.

I'm only familiar with the URL for the 2nd Xfil SSB Mod:

    http://www.elecraft.com/Apps/new_fil_docs/k2_2nd_xfil_ssb_mod.pdf

(Note, ALL spaces in the URL shown above are underscores "_", even though 
the auto-underlining of the link may tend to obliterate them)

I believe there are several of them awaiting being put up on the web site.

Go to the Elecraft web site, and take a look... there probably are others 
that I'm not remembering being listed there.

I'd put them up on my web site, but I have limited download volume and I'm 
pretty certain that it's disappear once I announced that they were there 
and available for download.

I know there are several folks here who have their own servers. If they'll 
drop me a note, I'll be happy to send them all of the mods I have IF they 
will make them available to users. I'd prefer to do it ONLY ONCE, and to 
several servers at one time, rather than piecemeal and repeatedly. What 
I'll probablt do is try to gather several takers over a couple days and 
then send them all at one time.

73,

Tom  N0SS