[Elecraft] 4 MHz Oscillator Mod for Easier Adjustment
John, KI6WX
[email protected]
Sun Aug 24 23:57:01 2003
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