Deluxe Memory Keyer with 3072-bit Capacity by W3VT (Robert C Cheek)

Discussion in 'Straight Keys - CW Enthusiasts' started by WA2FTV, Jun 4, 2019.

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  1. WA2FTV

    WA2FTV Ham Member QRZ Page

    Greetings Everybody,

    I am wondering if someone could provide some input/help. The following article is an improvement of the famous James Garrett WB4VVF Accu-Keyer. It was written by Robert Cheek (W3VT) in the April 1979 issue of Ham Radio magazine. The call sign W3VT appears to be a vanity call sign that is assigned to someone else, not Robert C Cheek.

    I can get parts from second source suppliers.

    I would like to duplicate the keyer portion of this design without the memory portion. The original James Garrett design used two transistors to generate the clock pulses. The W3VT design uses a 555 timer that is located on the memory board. There are two clock signals (CLOCK IN and CLOCK CONTROL).

    Does anyone have an idea of how to handle (where to connect) the CLOCK CONTROL signal that originates from the output of a 74123 through a diode on the memory board? The CLOCK IN signal is the output of the 555 on the memory board. The CLOCL CONTROL is an output from a 74123 IC on the memory board. The 74123 is a Retriggerable Monostable Multivibrator. Radio/70s/Ham-Radio-197904.pdf

    Any advice would certainly be appreciated.

    Thank You and 73s,

    Amateur Callsign WA2FTV
    Amateur Extra
  2. WA2FTV

    WA2FTV Ham Member QRZ Page

    It is on pages 32-43.
  3. K7MEM

    K7MEM Ham Member QRZ Page

    Your looking at it a little incorrectly. The CLOCK CONTROL does not originate from the 74123 on the memory board. That pin on the 74123 is a input. The CLOCK CONTROL signal, on the left side of the memory board schematic, is an input. The CLOCK CONTROL originates from the keyer schematic, U5-B Pin 8. This is a 7474 D-Flop. This signal is intended to sync the oscillator with the paddle.

    But the CLOCK CONTROL gets a little complicated, when you add the memory in the circuit. But if your not including the memory in your build, it really doesn't matter what it does. Your only concern should be, how CLOCK CONTROL gets to the 555.

    You can just simply use the two transistor oscillator, described in the original Accu Keyer schematic. Or, you can use the 555, an inverter (7404), in place of U3-B, to invert the CLOCK CONTROL signal, and a diode (CR1). This should provide the necessary synchronization to the paddles.

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