Encyclopedia of radio electronics and electrical engineering / Civil radio communications
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Schematic diagram of the EI9GQ key is shown in fig. 1. It (like all devices based on PIC controllers) is distinguished by its circuit simplicity, since the main weight is included in the program entered in the PIC controller. The key manipulator is connected to electrical communication lines 1 - 1 (3 - movable or "common" contact. 1 - dash contact. 2 - dot contact). Circuits R3C1 and R2C2 exclude the possibility of operation of the key from impulse noise and interference. The R1C5 circuit in combination with an external variable resistor (it is connected to lines 3. 4) sets the clock frequency of the controller oscillator and. hence the transfer rate. This variable resistor has a resistance of 5 kOhm and is switched on by a "rheostat".
The signal generated by the key is fed to the output transistor VT1. This node is designed for the most common "switching" option in modern transceivers - shorting to the common wire of the control bus (usually it has an initial voltage of +12 V). The current through the transistor should not exceed ten milliamps. The control bus is connected to line 7. If in a particular design the control current is greater or the voltage on the control bus is negative polarity, then a relay is installed in the collector circuit of transistor VT1, the contacts of which make the corresponding switching in the transceiver.
Diode VD2 is designed to protect the key from accidental contact with negative polarity voltage on the transistor, and when embedding the key in a specific design, it can not be installed. The key is fed from a +12 V source (it is supplied to line 6) through a parametric stabilizer on the VD1 diode.
PIC16C84 and PIC16F84 can be used in this design. A zener diode is of any low power for a stabilization voltage of 5.1 V. As a transistor VT1, KT315 or KT342 with any letter index is suitable, and the VD2 diode can be KD520A. The key is placed on a printed circuit board measuring 41x38 mm (Fig. 2).
The source code of the program in assembler (MPASM), the codes of which are entered into the controller's memory, is given in the table. The presence of the source text makes it possible for beginner "peak controllers" to get acquainted with the basics of programming.
(click to enlarge)
As can be seen from the comments to the program, this key provides both normal and "iambic" mode of operation of the key. The latter requires a special manipulator that allows simultaneous shorting to a common wire of the "dot" bus and the "dash" bus. This mode of operation, which appeared in the sixties in the tube telegraph keys, is characterized by the fact. that when you press "dot" and "dash" at the same time, it produces an "alternating" signal: dot-dash-dot-dash ... or dash-dot-dash-dot ...
It is called "iambic" because these rhythms resemble the poetic size of iambs (sing "ti-taa-ti-taa-ti-taa" - pure iambic). This is convenient when transmitting some letters that have such combinations (for example, the letters Ц, Я, К and others), since they are formed in this "one-click" mode (more precisely, by almost simultaneously pressing or "capturing" both heads of the manipulator). Which "iambic" letter will be transmitted is determined by which of the manipulator contacts will be closed first and how long the "capture" of the manipulator heads will last. The "yambic" mode of operation is very peculiar, but some radio amateurs like it.
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