[Elecraft] 4 mHz and C22 bandspread mod

[KEN BROWN]

I need to compare notes with anyone who has done the
bandspread mod to C22 and X2 4 mHz crystal (C21 replacement).
Extra 10 pF NP0 Vishay 1KV  75-10TSQ10 available for SASE. E-mail direct.
From: "John, KI6WX" <ki6wx@pacbell.net>
Date: Sun, 24 Aug 2003 20:51:50 -0700
Subject: [Elecraft] 4 MHz Oscillator Mod for Easier Adjustment
The reflector traffic seems to indicate that some folks are having
trouble
setting their 4 MHz oscillator to the desired frequency.  I added the
following changes to my K2 4 MHz oscillator about 2  years ago to improve
both its settability and its frequency stability.  The mod increases the
bandspread of C22 and significantly reduces the drift in the oscillator.
The drift reduction will only effect the K2 frequency accuracy if you do
a
CAL PLL at a different temperature than when you first set the 4 MHz
oscillator frequency.  I haven't tested this change on any other K2 so I
don't know if it will work for all 4 MHz Xtals.

The change requires two 10pF N750 capacitors.  Replace C21 with one of
the
10pF capacitors.  Solder the other 10pF capacitor across X2, the 4 MHz
Xtal.
With this change, the correct frequency is obtained with C22 in about the
middle of its range.  If you don't need the frequency stability
improvement,
you can use 10pF NPO capacitors.

If this change doesn't work in your K2, it can easily be backed out by
removing both capacitors and re-installing the original C21.

-John
 KI6WX


Ken Brown N4SO
Mobile, AL  EM50tk
K2  S/N 3394
  ELECRAFTK2@juno.com


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