Introduction

This page covers six or seven simple keyers. They don't contain all of the features that the more complex keyers do. But if all you want is simple, these should fit the bill. Some of these simple keyers are old and contain some long obsolete parts. I only include them here to show how long ago keyers were introduced.

Simplest Keyer by KU8K

I couldn't find a original article for this particular keyer. All I have to go by is this JPG.

Not much to say about this keyer. Its a very basic keyer can be constructed with just two relays, 3 capacitors, 1 resistor, and a diode. Your kind of stuck at one speed. The dot/dash timing is set by the 3 capacitors. Note that C1 and C3 are the same and set the dot time. C2 is twice the value of C1. When the dash paddle is closed, C1 and C2 are in parallel making the dash 3 times the length of a dot. To change the speed, change the capacitor values.

NE555 Keyer

This is probably the simplest keyer you will ever find. It only uses one IC, a few resistors and capacitors, a diode and a reed relay. Operation is pretty simple. Normally, with both paddles open, the NE555's output (U1-3) is a logic "0".

• When the Dot Paddle is closed, the NE555 initiates an output pulse who's time at a logic "1" depends on R3, C1, and R1 (470Ω).
• When the Dash Paddle is closed, the NE555 initiates an output pulse who's time at a logic "1" depends on R3, C1, and R2 (1.2KΩ).

If you hold the Dot or Dash paddle closed, the keyer should make a series of Dots or Dashes. However, holding them both closed will not generate alternate Dots and Dashes. It is probably best to use this keyer with a Single Lever Paddle. Even then, this keyer will at a little time to get use to it.

The QRP TLC-Keyer - Rich Littlefield, K1BQT

This keyer came from the January, 1990 issue of Ham Radio Magazine. It's a step up from the previous keyer, that used only one "555" timer. But it is still simple. The schematic below is a redraw of the original circuit.

There have been some modifications, like this web page by G4PPB. In that design, R7, which controls the dash and space length, is replaced by a 500KΩ, Linear Taper, variable resistor. C1, C2, and C3 are replaced with 4.7µF/16V Tantalum Capacitors. R7, and 82KΩ resistor, is replaced with at

The drawing below is a redraw of the single lever paddle included in the original article. The drawing is scaled at 160 dots/inch. It may be a little vague, but you should be able to fill in your own detail. It does provide a good starting point.

Errors and oversights. Ham Radio, January, 1990

• In the original article, U1-1 is listed twice. The author is showing pin 1 grounded on the device (U1) and also showing that pin 1 is used to ground the Paddle Common wire. I understand this, but it may be confusing to someone not familiar with old methods of drawing. It's just a roundabout way of grounding the Paddle Common.

Automatic Keyer Using Integrated Circuits - E. C. Reich, W5FQA

This keyer was published in the March 1967 issue of 73 Magazine. The intent of the article was to show how Integrated Circuits (ICs) can be used. Consequently, this keyer doesn't have any features, other than making continuous dots and dashes. But I still find it interesting. The IC used are from the Motorola SN73XX medium speed (up to 4 MHz) diode-transistor logic series. They are currently obsolete, but more up to date circuits could be used. If CMOS ICs were substituted, the power structure could be simplified.

The Unijunction Transistor (Q1-2N2646) was popular at the time. And, even after all these years, it is still available. Although it is rarely used. But it does make a very nice relaxation oscillator. The signal on Q1-B1 is normally "low" (-9V) and pulses "high" very sharply and then decays "low" again exponentially. The rate at which it pulses is determined by the value of R1+R2 and C3. This rate is also the Word Per Minuite (WPM) rate. For this keyer, the WPM rate works out to 2 to 93 WPM. That's a little excessive, on both ends. If one were to actually build and use this keyer, it would be best to adjust the values of R1 and R2 so that the range is a bit more reasonable.s C5 and R5 form a "differentiator" that produces a pulse with a sharp rise and fall time for the flip-flop.

Of interest, might be the power setup. The keyer is made to run off of a 9 Volt battery. But the ICs should only run on 3 to 4 Volts. So the author employs a 5.6 volt Zener diode (CR3-1N4734) to reduce the voltage for the ICs to 3.4 Volts. This tends to obscure some of the logic levels. For example, the Paddle Common is shown tied to ground. But logic wise, the ICs are referenced to -9 Volts and ground is 3.4 Volts above that reference. So the Paddle Common is really held at a logic "1". Closing the dot or dash paddle cause a logic "1" to appear at the "K" input of FF1-A and FF1-B.

Note, if you view the original article, in the March 1967 issue of 73 Magazine , you might notice that there are several errors in that schematic.

• The Reference Designator CR3 is used twice. Once, on a 1N4001 diode, and again, on the 5.6 Volt Zener diode. The Reference Designator for the 1N4001 should be CR2.
• FF1 (J) shows pin 15 going to ground. But FF1 only has 14 pins. That pin (J) should be labeled pin 5.

Keyer On A Shoestring - Joel R. Donaldson, WB5PPV

This keyer was published in the November 1982 issue of 73 Magazine. It is probably one of the simplest keyers that I have ever seen. If you hold the Dot Paddle closed, the Dot Oscillator will generate continuous dots. The rate is set by R3/C1. If you hold the Dash Paddle closed, the Dash Oscillator will generate continuous dashs. The rate is set by R4/C2. The variable resistors R1 and R2 are intended to be "ganged", so that they both turn at the same time. R5 is then used to make the Dash Oscillator run a bit slower than the Dot Oscillator.

The output of the Dot and Dash Oscillator signals are ORed together with diodes D1 and D2, and drive the keying transistor Q1. The keying is intended for newer solid-state transmitters or Cathode keyed tube transmitters. The keying circuit, of course, could be changed for Grid-Block keyed transmitters.

The output transistor, Q1, has a Radio Shack number. The RS 276-2008 is a NPN Medium Power Amp with 1 W Dissipation, VCBO = 300, VEBO = 7, Ic = 30mA, Hfe = 40. Any equivalent transistor should work.

The Sidetone Oscillator is keyed by the output of D1/D2 and runs at a rate of about 1,000Hz. That can be changed by adjusting the values of R7/C4.

Since this keyer doesn't respond well to enabling both the dot and dash oscillators at the same time, it will probably be best if this keyer is used with a Single Lever Paddle.

It is important to note that, the Common contact for the Single Lever Paddle is connected to +9 Volts. Normally, in most other keyers, this is connected to ground.

My version of the schematic is a little bit different than the original. The original was just a couple of rectangular boxes with wires sticking out. I also left out the power switch. The original power switching was configured so that the keyer could be run without the Sidetone Oscillator being enabled. If you don't want the Sidetone Oscillator, eliminate it. I also didn't bother with writing a Verilog simulation. A simulation wouldn't add anything.

ELBUG - Simple CMOS Keyer - OH7SV

Simple Keyer - Vasile CIOBANITA YO3APG (SK)

I couldn't find a original article for this particular keyer. All I have to go by is this JPG. The first page contains the Keyer clock, keyer logic, and keying relay circuit. The second page contains power wiring and the Tone Generator.

Basic Keyer - James H. Fox, WA9BLK

This keyer was included in a article by James H. Fox, WA9BLK in the January 1975 issue of QST Magazine. It article included a keyer and a T/R switch, Power Supply, and even an optional keying circuit. However, I will only include the keyer portion. If the T/R switch, Power Supply, and keying circuitry interest you, see the original article linked above.

The operation of the keyer is pretty straigh forward. Closing either the Dot or Dash paddles, will start the keyer clock. The clock will continue to run as long as either of the paddles are closed at the cycle time.

The output of the keyer is in the upper right, comming off of U2-A Pin 13. And example waveform using the letter "C" is shown. This output can drive almost any transmitter keying circuit available on the Keyer Extras page. The output levels, 0 and 1, are standard, positive logic, TTL signals.

You might notice that there are several input signals pins, on U2 and U3, that are not connected. Usually, you would find these unused pins ties to VCC through a 1 to 10 K resistor. However, this is acceptible practice with standard TTL devices. The unconnected input signals will assume a logic "1". If you are trying to figure out the operation of the logic, you should note that the SN7473 is a Master/Slave Flip-Flop. J-K input is loaded into the Master while the clock is High and transferred to the Slave on the high-to-low transition. This is different than the SN7473A.

For a detailed explanation of the operation, refer to the original article linked above.

Morse Keyer - A. P. Cooper

This keyer was included in a article by A. P. Cooper in the August 1983 issue of Practical Wireless. This is another very simple, but usable, keyer. The SN74LS221 is a dual version of the SN74LS121. The switching characteristics are almost identical. However, the pinout is identical to the SN74LS123.

Note that the speed control pots, R2 and R3, are ganged. The keyer will make the dots and dashes, but you are in control of the element, character, and word spacing. This keyer is best used with a side swiper type key.

The original drawing had the CW_OUT signal going to a buzzer. You can still use a buzzer but you can also use the CW_OUT signal to drive a Cathode Keying or a Grid Block Keying circuit.

Ramsey Electronics Model No. CW7

This keyer was produced and sold by Ramsey Electronics as the Model CW7. Ramsey sold this keyer as a kit for only $5.00. I would have though that there was more than $5.00 worth of parts alone. But I guess I was wrong. It seemed to do what was needed.

The first page contains the keyer logic. The second page contains the Side Tone Generator and Power wiring. The keyer will work with either a single or double paddle. In fact, the user manual contains rough plans for making your own key. I did find it odd, however, that you can find the user manual on the internet, but none of them included the schematic. You get complete instruction on assembling the CW7 but the pages that are reserved for the schematic are blank. So the drawings below were reverse engineered from the PCB layout, that was included in the user manual. I double checked the drawings against the PCB layout, and looked at the design logically. So I don't think there are any errors.

1978 Radio Handbook Keyers

The following two keyers were listed in the 1978 Radio Handbook that was attributed to William I. Orr, W6SAI.

I was kind of surprised at this first one. In the original drawing there was no reference to part values. I made a educated guess at IC numbers and drew it like I think it should have been drawn. Maybe it was the way they drew logic in 1978, but I don't think so. I guess they were just trying to portray an idea. The original specified a two contact key, which is the same as the single paddle that I show. The circuit is not Iambic. Also note that power and ground for the ICs is not shown.

They did a lot better with this next one. Although the original was still missing power and ground for IC1. And IC1, a SN7400, is drawn two different ways. Two instances are drawn as NOR gates and two are drawn as NAND gates. While they are used as inverters in two cases, a SN7400 is a NAND gate package.