Fw: [Elecraft] 4 mHz and C22 bandspread mod

[Mike Harris]

G'day,

Time flies, I didn't realise it was so long since this was posted.

Regards,

Mike VP8NO

----- Original Message ----- 
From: "KEN BROWN" <elecraftk2 at juno.com>
To: <elecraft at mailman.qth.net>


| From: "John, KI6WX" <ki6wx at 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