August 1966 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
A lot of innovation went
into perfecting telegraph keys. The earliest keys were the familiar "straight key" tapping type where the operator uses a single finger to
close a set of contacts that "keyed" the transmitter for a burst of RF energy. The
length of each "dit" or "dah" was determined by the operator's dwell time. It didn't
take long for someone to improve on the scheme by designing keys that assured an
adjustable, constant length for a dit or a dah. Poor quality transmitters with lousy
rising and falling edge signatures at the beginning and end, respectively, of a CW
(continuous wave) pulse made matters worse. Constant length bursts make it easier for
the person on the receiving end to copy since patterns do not depend so much on the
sender's "fist" style. Eventually the electrical, mechanical, and human elements got
good enough that code sending / receiving speed was limited by the amount of time
taken to physically open and close the key contacts. A stronger return spring makes
the contacts open faster, but it is harder to depress and slows operation. Horace
Greeley Martin, proprietor of the Vibroplex Company, introduced the "bug" style telegraph key in
1905 to address the issue. The Vibroplex has a set of contacts on both sides of a
paddle that moves back and forth horizontally between the user's thumb and
forefinger. That removed the need for a strong spring (only enough force to center
the paddle) and allowed the operator to very rapidly shake his wrist to generate
code. A newer type bug, referred to as a
paddle, has adjustable circuitry that generates fixed proportion
dits, dahs, and spaces. They are referred to as "iambic"
due to the fixed meter (cadence) generated.
The Dit Makers -Converting Muscle Power to Morse Code Was the Job of These Old Workhorses
By Marshall Lincoln
Although this statement may start an argument, the heyday of the radiotelegrapher
has passed. Since Marconi keyed his first transmitter, however, there have been all sorts
of ingenious contraptions developed to ease the job of the radio operator. Looking back,
many key designs now seem rather foolish and scarcely worth the effort involved in learning
how they were to be used.
You'll find old keys, proudly polished , exhibited in the many "wireless" museums
that dot the country. The keys shown here are on display in the museum maintained by
the American Radio Relay League, in Newington, Conn.
Think a "bug" is a complicated machine? How would
you like to drive this impressive unit down the 80-meter ham band? You might call this
a "double bug," although its proper title is "double lever automatic keyer." It formed
dit's and dah's automatically, like a "modern" electronic keyer, but the operation was
entirely mechanical. There were 17 adjustments to make to tune it up for use - you had
to be a good man to get 'em all done before the sunspot cycle changed.
This is a "sideswiper." Also called a "cootie
key," it was the granddaddy of the modern "bug" or semi-automatic key. The sideswiper
was made with a spring lever suspended between two fixed (but usually adjustable) contacts.
Both dit's and dah's had to be formed manually by the operator. The large silver contacts
on this "dit maker" were said to be capable at handling 2000 watts.
Take a look at the mounting bolts on this baby.
It's just a simple straight key that was the standard type used on United Fruit Company
vessels. The long bolts held the key securely bolted to the operator's worktable. The
contacts aren't exactly midgets, either - those sea-going spark sets really packed a
You might call this one a bug in a box. It's
an early type of semi-automatic key which was called a "Mecograph," and is shown here
in its carrying case. It had a paddle much like those used on bugs today, but the weight
and pendulum that form the dit's are at right angles to the paddle axis.
Who says "CQ" wheels are new? This old-time "Omnigraph"
was made in the early 1900's for transmitted interval signals to occupy the frequency
or channel. A spring-powered clockwork at the right (notice fly-ball governor) turned
the wheel in the center, which carried metal "code wheels." Raised spots on the edges
of the wheels caused a spring lever to close electrical contacts, keying a transmitter.
This heavy-duty key saw some hard use. Notice
the angle of the large contacts. Those big lumps of silver could handle a kilowatt with
ease. They had to. The old-time transmitters were big bruisers, and the "main plumbing"
was keyed directly. The old key slappers weren't called "Sparks" for nothing.
Posted April 10, 2018