ZS6ANW/TPK 1.83d. Bdsk: N§135  Datum: 02-05-2002  Tyd: 6:59 SAST (-2 ure = Z)

>From: ZS6FB@ZS6FB.MPU.ZAF.AF
>To  : ZS6ANW@ZS0TFK.LIC.NWP.ZAF.AF
>
>Hello Joe,
>
>How about putting your xtal checker out @WW. I am sure it would be appreciated.
>
>73...Bob

Thank you for your comment Bob, trust you are keeping well....no problem, here
with the Crystal Checker going out @WW...

73 de Joe ZS6ANW
----------------------------------------------------------------------------
    Om  Petrus,  ZR6DPH  asked  me for the circuit  diagram  of  my  crystal
    checker.  As  I  spent quite some time drawing the circuit,  I  decided
    that  I  would  share it with other technical minded  packet  users who
    might be interested in this handy piece of equipment.

    I  have used it on many occasions for checking fundamental HF  crystals
    on  "GO-No-Go" basis, but also to check their fundamental frequencies.
    Although  not shown on the diagram, in my unit, I have installed a jack
    plug  (connected  to  C3 via another 1000pF capacitor) so as  to  enable
    connection with a frequency counter.

    Basically  the above circuit is an untuned Colpitts oscillator driving a
    voltage  multiplier  rectifier and a current amplifier. If the  crystal
    oscillates, TR2 conducts and the LED lights.


                                             SWITCH
            ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄ/ÄÄÄÄÄ¿ +
            /         ³                  led      B
            \ R1      ³                  /         A
            /      b / c                 \ R3      T
            ÃÄÄÂÄÄÄÄ´ TR1     D2      b  / c       T 9 VOLTS
            ³  =C1  eÃÄÄÄ×ÄÄÂÄÄÄÄÄÂÄÄÄÄ´TR2       E
     CRYSTAL²  ÃÄÄÄÄÄ´   C3 ³      ³     \ e       R
            ³  =C2   /R2    D1    =C4   ³         Y
            ³  ³     \      ³      ³     ³         ³
            ÀÄÄÁ--ÄÄÄ/ÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁ  -

             R1 = 39K   C1 = 680 pF   D1 D2= OA91 or 1N34
             R2 = 1K    C2 = 150 pF   TR1, TR2 = BC 107, 108 or 109
             R3 = 100ê  C3 = 1000 pF
                        C4 = 0.0047æF


   73 DE JOE ZS6ANW