Ever since Samuel Morse tapped out his famous “What hath god wrought.” message in 1844 on the primitive code key he devised others have tried to improve upon each element of the system. This resulted, by the time the last major telegraph offices were shuttered well over a hundred years later, in a multitude of different key designs and concepts. Very likely many thousands of different designs.
The straight key, as it is known, is familiar to all….it is the direct descendant of what Morse developed and would remain recognizable throughout the telegraph’s reign and beyond. But it had two major disadvantages. Speed, for one….a person can effectively only operate the device so fast…up to maybe 30 wpm…but more importantly, what became known as “glass arm” began to afflict professional telegraphers. Today, we know the condition as a repetitive stress injury. It is a debilitating condition that sent many good telegraphers into early retirement.
In an effort to combat these shortcomings, a variety of contrivances were designed. Keys that operated as if by a paddle using a side to side motion were certainly a step in the right direction. While the initial concepts did little for sending speed, they did reduce the fatigue issues. By 1904, Horace Martin patented his semi-automatic speed key, commonly called a “bug.” This is what became the famous Vibroplex keyer. It utilized a spring equipped lever with adjustable weights. By pushing the knob side towards the left, one could manually tap out a “Dash” …but by pushing the paddle from the other side towards the right, a “Dot” would be generated. Furthermore, holding the lever in this position would allow the spring to oscillate, giving a series of “dots” in rapid succession. Adjusting the position of the weights altered the period of the pendulum effect and thereby changed the speed. Releasing the paddle brought the lever in contact with a damper to stop the process. In this way, a competent operator could send at speeds in excess of 45 words per minute! …and do it without risk of physical wear and tear on their hand!!
The Vibroplex, and other keys that copied the concept (often infringing upon Martin’s patents) became the standard in telegraph offices and later, radio rooms, the world over. They are a mechanical marvel and are still produced to this day for amateur and shipboard radio operators.
Today, many who operate CW (continuous wave, morse code on the air) prefer to use an electronic keyer and a set of paddles. The Iambic paddles are nothing more than a pair of switched paddles, one for dots and one for dashes, that are connected to a multivibrator type electronic circuit. This has several distinct advantages over the “Bug” keys. The electronics in the keyer generate all the keying pulses for both dot and dash. The duration and spacing, as well as the speed, are all adjustable and once set they remain more consistent than a human can do. Ideally, a dash should be three times the duration of a dot and the spacing between each should also be uniform. The electronic keyer insures this is always the case. Since WWII, all sorts of electronic keyers have been designed and built–in home shops, as well as commercially sold products.
One of the very earliest, if not the very first, was the “Mon-Key” that was sold by the Electric Eye Equipment Company in 1948. Electric Eye was primarily in the business of producing controls and other products for industry that worked on the principle of a photoelectric sensor that would detect the presence or absence of a beam of light and then switch on or off some function. Today, you might be most familiar with this idea in the safety switch on garage door openers or the sensor on top of a street light that turns them on when the sun goes down. What got Electric Eye into the radio equipment business is not certain, but they did have moderate success putting the “Monkey” in charge of sending code.
The Mon-Key uses three tubes, one is a 35W4 rectifier and the other two are both 12AU7 types. The filaments are wired in series and powered directly from the line, those familiar with tube types will note that this adds up to 59 volts for the string. Therefore, some other resistance is needed to keep from burning them up on 110v line power. The Mon-Key used a three wire cord on a two prong plug. The third wire is a resistor lead running the length of the cord. This lead is tied to the filament circuit. And, yes, the cord feels warm when it is operating. Don’t worry, that is normal. If you have one of these. Do not cut the cord short, or you’d be shy of resistance! If one must replace the cord, you will need to add a power resistor inside the case to keep the tubes happy. Another power related feature that is apparent in following the schematic is that there is no isolation transformer (a common practice at the time) and therefore, depending upon how the non-polarized plug is inserted, the key contact parts can be at line voltage! Beware! Hence the clear plastic dust cover over them!
The unit is simple to operate and does a decent job. I have not tried this on the air, but after some minor work it seems to function as expected and although a bit of an anachronism, it could safely key even the most modern of tiny transmitters since the keying relay output is fully isolated. I may have to try it on my FT-817 just for the heck of it.
The speed selector gives a range of about 8 to 45 wpm. It is possible to modify this range up or down by altering the values of the capacitors marked C1 and C2 in the schematic. The manual recommends adding .005 mfd mica caps in parallel with C1 and C2 in order to lower the speed range. Note that if both caps are equally altered then a uniform speed reduction will occur. However, if they are not equal, bad spacing or improper pulse duration will result.
Compared with more modern contrivances, the Mon-Key is very basic. But at the time, it was as high tech as could be had and it helped usher in the next era of automatic technology as they made it so easy a monkey could do it.
Mon-Key Video demo:
Thank you for an interesting article. )^_^) Gary KI7TRP