Crystals (FT-243) in a novice transmitter - help.

Discussion in '"Boat Anchor" & Classic Equipment' started by K9UR, Nov 10, 2021.

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  1. K1APJ

    K1APJ Premium Subscriber QRZ Page

    I hear ya-

    Many re-stuffed FT-243s work acceptably well with my Drake 2-NT. Few work well with my Heath HW-16. YMMV
     
  2. SM0AOM

    SM0AOM Ham Member QRZ Page

    Your problem is most likely the Pierce oscillator in this circuit:

    upload_2021-11-11_7-21-34.png

    They subject especially small crystals for far more current than they are designed for.

    73/
    Karl-Arne
    SM0AOM
     
  3. K9UR

    K9UR Subscriber QRZ Page


    Bought some HC 49 from the AF4K web site. Let’s see. If not then I guess a DDS project is on the horizon.
     
  4. K9UR

    K9UR Subscriber QRZ Page

    Is there a solution to reduce that current or is this the laws of physics ?!
     
  5. SM0AOM

    SM0AOM Ham Member QRZ Page

    Reducing the plate voltage and reducing the value of C1 may help,
    but it is not certain.

    Modern crystals are not designed for the drive levels used "yesteryear".

    73/
    Karl-Arne
    SM0AOM
     
  6. W9BRD

    W9BRD Ham Member QRZ Page

    2-NT uses a small-signal receiving pentode as its crystal oscillator (grid-plate circuit); HW-16 uses a power pentode (6CL6) as a Modified Pierce. That's the reason.
     

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