I have been collecting bugs for just a short time (unless you count my first one which I
acquired in 1954) and have found it to be an interesting adjunct to the ham radio hobby.
Bugs, or semi-automatic telegraph keys, are collectible items which don't cost large
amounts of money (yet) and are interesting links to radio history. The original telegraph
keys used an up and down motion to produce dots and dashes. Sending at high speed with
a original or "straight key" was fatiguing and prompted development of easier ways of
sending Morse code. In 1888, the Bunnell Company introduced a key which had two sets of
contacts and used a horizontal motion to make dots and dashes, improving sending
efficiency by a factor of two. Horace Martin received a patent in 1903 for a key which used
an electromagnetic scheme similar to a doorbell buzzer to make dots (the Autoplex). It
didn't become popular as it was difficult to adjust and had to be readjusted frequently as
the batteries powering it became weaker with use. He also applied for a patent on a
mechanical semi-automatic key in 1904. Unfortunately, another gentleman (Coffe) had
applied for a patent several months earlier and this all resulted in several lawsuits. Neither
of the original bug designs worked very well. Martin solved this problem with the
Vibroplex which was introduced in 1905 and patented in 1906. Rather than simply
releasing the spring-mass system to make dots, his new design energetically put the
pendulum into motion when the dot lever was moved. The original model is still available
from the Vibroplex Company, indicative of a design which truly has stood the test of time.
The basic idea of the bug was to reduce operator fatigue by automating the sending of
"dots", which are nominally one third the length of "dashes". This was accomplished by
using a spring-mass system which was activated by pushing the lever to the right. Dashes
were made manually, by pushing the lever to the left. A few attempts were made to also
automate the production of dashes, but their long length and synchronization problems
between the two arms meant that these fully automatic keys weren't successful. For those
that recall Physics, a spring-mass system will oscillate in a sinusoidal fashion with an
exponential decay due to frictional effects and wind drag. Since a dot and a space are the
same length, it is fairly easy to set up a bug to produce dots and spaces whichare athe same
length. The problem with dashes is that they are three times as long as a space, so
automating the production of dashes would require offsetting the contact from its natural
position to the point where the dash length would change substantially if several dashes in
a row were needed ( the number 0 is 5 dashes). In the 50's designs for electronic keyers
began to appear in ham magazines, and I built one using a Thyratron (anyone remember
that this was a gas discharge triode?) and used my bug (with the pendulum inhibited from
moving) to actuate the keyer.
Referring to the picture below, the main parts of a typical bug are identified. The base is
usually iron or steel, to provide enough weight to keep the bug from moving around while
in use. The yoke is used to hold the moving arm as well as incorporating stops to limit side
to side movement of the moving arm. The mainspring connects the moving arm to the
pendulum, to which movable weight(s) are attached to allow dot speed to be varied. The
damper stops the pendulum after the operator has made the desired number of dots
(number 5 consists of 5 dots, the most of any radio Morse character). The operator uses the
finger pieces to operate the key.
A trio of Vibroplex bugs are shown below. At the right is a recent version of the Original
model, the middle one is a Blue Racer, which is similar in construction but with a narrow
2.5 inch wide base and at the left is a Lightning model, which has a yoke and damper
support which is built-up using spacers and plates instead of the castings used in the
others. The latter two keys are no longer being manufactured. The Lightning also uses
rectangular weights mounted on a flat (rather than round) pendulum.
The same keys from the
damper end with the Original
on the left and the Lightning
on the right.
The Mac key shown below was made during the late 30's by "World Champion
Telegrapher Ted McElroy (who set a record which still stands copying 77 wpm). It has two
unusual features, the marbleized finish and the yoke which had extended ears allowing the
key to be turned on its side and used as a straight key.
The Electric Specialties Company (Cedar Rapids) key is shown below. It was available as a kit and was a simple, no frills, design. The only unusual feature was the use of an O-ring on the damper wheel.
I acquired my first bug (shown below) in 1954 at a hamfest. It doesn't have any markings and there are no holes for a nameplate. It could have used a decal for identification, of course. Thus far, I have been unable to identify the manufacturer. It has a cast yoke of a different design than that used by Vibroplex in that the extension arms hold the pivot bearings for the moving arm and the stops and dot return spring are on the main yoke. This basic yoke design is also used in the Mac keydescribed previously, although the Mac key had substantial detail differences. The pendulum arm is the same diameter as used by Vibroplex and the damper is a simple wheel mounted loosely on a post. The base (3.5 in x 6.25 in) has mounting holes so that it can be securely attached to the operator's desk. The dot lever also has an unusual shape, biased for an operator that likes to rotate his wrist slightly so that the thumb is lower than the first finger. If you have some info on this key, please e-mail me.
An interesting website with a lot of info on telegraph keys is Sparks.
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Last Updated April 3, 2000 by Robert Bicking