A keyer is an electronic circuit connected to a two-paddle Morse key (a.k.a. bencher
key or horizontal key or automatic key or iambic key) and to a radio transmitter.
Left paddle transmits dots, while right paddle transmits dashes. Pushing the right paddle while keeping pressed the left one, transmits a dot, then a dash and another dot. Keeping pressed the two paddles, continues the dot-dash sequence, until one of the paddles is released. The same thing happen if you press the right dash and then the left, resulting in a dash-dot sequence.
Transmitting this way is far more simple and quick than using a standard vertical Morse key, thus many radio amateurs use iambic keys. Modern transmitters have the keyer circuit built in. An external keyer, like this one, is useful for old transmitters and also for new ones, because of the other features it delivers: the message memory, the beacon mode, the possibility to practice Morse.
My keyer is based on a Microchip PIC 16F84 microcontroller and it uses a small
number of components. You only need a crystal, a transistor and a few
capacitors, resistors and connectors, plus a small speaker and a button.
By the way you also need a small box and some batteries, just to give the
3.5 to 5 Volt DC the keyer needs.
The current is below 30 mA, with led glowing yellow and the speaker on. During pauses current drops to less than 20 mA and to only a few microamperes in sleep mode (for this reason there is no on/off switch).
A printed circuit board is not mandatory for this circuit, because of the small number of components.
If you are lucky enough to live not too far from my home (which is unlikely if
you are reading in English), I will be happy to give you one chip programmed with
the keyer software I developed for this project.
Otherwise, keep reading and you will find the hex module you must put inside the 16F84 chip. If you don't have a chip programmer circuit, normally connected to the serial, parallel or USB port of your computer, you can buy it or look for a radio amateur owning it and kind enough to program the chip for you.
You can download here the hex module you need to program the Microchip PIC 16F84
you need for the keyer. This is the software for version 2.2 of the keyer.
Be sure tu match the software version with the circuit version (below you will find
some older versions).
The zip archive contains the circuit drawing, this page and the hex module.
The use of the keyer is basically identical to the previous version 2.1,
but I totally rewrote the manipulation (iambic) routine, after some enthusiasts of very
high speed CW criticised a bit my keyer. I think now iambic is ok even for these strange
Due to difficulties to find 4-bits (thus 5 pins) 16-positions binary rotary switches, I mapped the positions A through E also on positions 5 to 9, that were unused before. So now, for example, to set audio on/off you can rotate the switch to 5 or to A, at your choice. This means that you can now also install a 4-bits (5 pins) 10-positions BCD switch, witch is more easy to find.
For the same market reason, I decided to support both 2 and 4 MHz quarz crystals, but for this you must tell the chip in some way (no, wispering doesn't work...) what crystal you are using. Since I got 2 unused pins, one of them is used now for this purpose. So, leaving pin 13 of the 16F84 free (logic 1) tells the chip that you are using a 2 MHz crystal (this is compatible with previous versions of the circuit), while connecting pin 13 to ground (logic 0) tells the chip that you are using a 4 MHz crystal.
All these changes were possibile because I changed the way to compute delays for each transmitting speed. Up to version 2.1 I used a pre-computed table stored in program memory, but now I execute a division routine and the space occupied by the table is now used for real istructions.
Thus I could add also a new feature to direct mode: pressing the button will trasmit a 5 seconds carrier, very useful for tuning.
I prolongued also the timeout for sleep mode, from the very short 33 seconds to a more normal 2'45". This doesn't affect the way you use the keyer, it's only a psycological trick: the keyer doesn't look dead while listening in a CW QSO.
Finally, I measured the actual trasmitted speed of the keyer and found it was about 9.8% slower than it should have been. Not a real problem, but I tuned delay constants anyway.
The following table shows how to operate version 2.2 of the keyer.
|Status||LED color||Left paddle||Right paddle||SET button|
|0||Sleep||Off||No effect||No effect||No effect|
|1||Ready||Green while rx.
Red while tx.
Yellow if tx local.
|Dot||Dash||Send single CQ message|
|2||Speed||Yellow||Decrease speed||Increase speed||Sound current speed|
|3||Weighting||Yellow||Decrease weight||Increase weight||Sound current weight|
(Wn or Wn.5)
|4||TX||Green if disabled.
Yellow if enabled.
|Enable transmitter||Disable transmitter||Sound status|
(TY or TN)
|5 or A||Audio||Green if disabled.
Yellow if enabled.
|Enable audio monitor||Disable audio monitor||Sound status|
(AY or AN)
|6 or B||Beacon||Green if message present.
Off if no message.
|Starts Beacon sequence.
During carrier: immediate call.
|During call: go to carrier.
During carrier: more carrier.
|Starts Beacon sequence.|
During tx or carrier: stops Beacon sequence.
|Autostart beacon sequence at power on|
|7 or C||CQ||Green if message present.
Off if no message.
|Starts CQ sequence.
During pause: immediate CQ.
|During CQ: go to pause.
During pause: more pause.
|Starts CQ sequence.|
During CQ or pause: stops sequence
|8 or D||Direct||Green||Carrier while pressed||Carrier while pressed||5 seconds carrier|
|9 or E||Enter||Green||Store a dot||Store a dash||Single pressure: insert inter-word space.|
2 consecutive pressures: delete last char.
|Store an inter-character space when pausing 0.25 sec.|
|F||Sleep||Off||No effect||No effect||No effect|