On 20M, about 14.030 5khz one would hear a signal when the keyer was
activated. I checked it out with a Ten Tec Corsair; (one of the quietest
receivers know). Only the ground side of the keyer output was connected
to the rig; (one wire). A S9 signal was noted. Without the wire
connected it was about S3. The major signal is conducted and not
radiated. I replaced the keying output transistor with an optoisolator,
NTE 3098. The optoisolator has four leads. Two are connected to a diode,
the remaining two are the transistor collector and the transistor
emitter. The two wires that key the rig are not electrically connected to
the keyer. (Also, changed the associated resistor.) With the addition of
the optoisolator the signal is now S3. The Super CMOS III Keyer is
powered by 3 AA cells. In addition to this change, a darlington power
transistor replaced the speaker output transistor. This has been
operating for over three months without the strong spur on 20M and a
audible sidetone.
Before this circuit is recommended the output drive current of the
microprocessor needs to be checked. I have not verified this.
I operate HF cw mobile using a bugcatcher antenna going to work and back
home. The trip is about one hour. I purchased the Super CMOS III keyer to
use in the auto. The Super CMOS III Keyer instruction stated to put the
keyer in a metal box. Metal parts are too hot to handle while left in the
car. I put the keyer in a plastic box.
Mark K5GQ
ARRL VE
Location: 29.958 N 95.495 W
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