QST for August, 1967 described a solid-state version of the
popular W9TO keyer. This project by K3CUW also appeared
in the ARRL Handbook during the late 60's and early 70's.
The original "TO" keyer used vacuum tubes, while the integrated
circuit version sported small integrated circuits by Fairchild
Semiconductor. These ICs were fabricated with RTL (Resistor-Transistor
Logic) and looked much like small signal transistors except
for their 8-lead construction and epoxy cases.
Two early 1970's Fairchild
uL923 JK flip-flops and a uL914 logic gate.
used the copyrighted name MicroLogic ® and uLogic®
for their first ICs.These
ICs were some of the first sold commercially.
ICs implemented basic logic functions and contained about
15 transistors with some internal resistors. This is why
they were called RTL (Resistor-Transistor Logic). RTL
was an early technology and soon gave way to more noise
immune and faster devices in the DTL (Diode-Transistor
Logic) and TTL (Transistor-Transistor Logic) families.
I had already successful constructed the W9TO vacuum tube
keyer, I decided that a smaller and more efficient IC
version of the project was for me. My young ham radio
friend, Gary Straub WA8RXQ (later K8BU and now a Silent
Key) constructed this keyer too. However, we both had
the same problem that spurious dots would sometimes occur
in the code pattern. We both carefully checked our construction
for assembly errors, but all appeared according to the
After seemingly endless checking we were baffled. I wasn't
entirely comfortable debugging the IC logic. This after
all was my very first IC digital project and it
was a bit intimidating for a youngster.
A while later Gary called me with the news that he had
found a fix for the circuit after experimenting with bypass
capacitors. He said that apparently a glitch was triggering
one of the integrated circuit flip-flops and that the
addition of a single 1000-pf capacitor to the signal lines
between the two IC flip-flops added enough noise immunity
to eliminate the false triggering!
was good news indeed. My Micro TO keyer project then worked
after I added the glitch suppressor capacitor, and I started
using the new keyer on the air.