Serious CW operators know that a
paddle is the way to go to make CW easy and fun. But along with
the paddle, a certain amount of electronics is needed to produce
the necessary dots and dashes. This circuit in figures 1a and 1b
is a simple keyer which can be built for as little as $6 with
some junk box parts. Although this circuit is not a true iambic
keyer, it is capable of producing perfectly sounding CW. To make
construction easy, all parts are available off the shelf at any
Radio Shack store.
The circuit in figures 1a and 1b
uses a quad NOR gate chip and a dual-D flip-flop chip. Two of the
NOR gates are used as the clock generator and the frequency is
determined by C1, R1 and R2 which sets the keying speed. This
clock signal is fed into Pin 3 of IC 2 which is the dot flip
flop. Nothing happens at this point until the dot paddle is
grounded. When the dot paddle is depressed, Pin 1 of the flip
flop changes states for as long as the dot paddle is depressed.
When the dash paddle is grounded, this in turn causes the dot
paddle to be grounded also through Diode D1. This starts the dash
cycle which continues until Pin 13 of IC-2 changes state again.
Diode D2 keeps the dot paddle low until the dash cycle finishes.
Pins 1 and 13 of each flip-flop form the output to transistor Q1.
Because Pin 1 is not always high during the dash cycle, Diodes D3
and D4 form an OR gate to keep Q1 turned on during a dash cycle.
This circuit has one anomaly which
operators should be aware of. The dash paddle always has priority
and attempts to squeeze the paddle (both dot and dash depressed)
results in a continuous stream of dashes. This means the operator
must release the dash paddle before depressing the dot paddle.
Experienced CW operators will have no problem with this circuit
but sloppy high speed operators will need to refine their sending
since it is not as forgiving as a Curtis chip.
This circuit uses CMOS chips which
require special handling to prevent static charges. IC sockets
are highly recommended. The circuit requires very low power and
can be powered from 8 to 15 volts. A 9 volt battery should last
several months meaning an on/off switch isn’t needed. No weight
control is provided because experience has shown that it is often
misused by operators causing code which is difficult to copy. A
shielded enclosure is required and capacitors C2 and C3 should be
soldered as close to the paddle jack as possible to keep RF out
of the circuit. This circuit was constructed on a Radio Shack
multipurpose pc board (RS 276-150) and no printed circuit board
is available for this project.
resistor, � watt 5% tolerance (RS 271-1347)
potentiometer (RS 271-211)
� watt 5% tolerance (RS -271-1335)
microfarad capacitor (RS 272-1070)
microfarad capacitor (RS 272-1065)
or similar diode (RS 276-1122)
similar NPN general purpose transistor (RS 276-2009)
4001 quad NOR
gate (RS 276-2401)
D-type flip-flop (RS 276-2413)