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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Telegraph machine for repeater. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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According to the new rules, each repeater must have his own call sign and at least once every fifteen minutes report it by telegraph on the air. Somehow I happened to make a similar machine based on a PIC processor. I will be glad if this design is useful to someone.

Telegraph machine for repeater
(click to enlarge)

The program is very simple and contains two telegraph words. This is the call sign and additional information, such as the last name. The call sign is telegraphed immediately after the voltage is applied to the circuit, and the second word is transmitted after the call sign only if the S1 toggle switch is turned on. Ten minutes later, the machine switches on the transmission again and telegraphs. But only if there is no voltage at the "squelch" input, i.e. the transistor is closed. This is done so as not to interrupt rare DX by telegraph. But you can not connect this input at all, then the conversation will be interrupted by a telegraph message, this is done in most cases, the S3 toggle switch is provided for this. Relay P1 turns on the transmission and switches the low-frequency microphone circuit. You can force the machine to start by briefly pressing the S2 toggle switch. While it closes the reset signal to the ground, the machine does not turn on. This allows you to use this design as a beeper for the operator of an individual radio station.

Programming a callsign is also easy. For example, the call sign RR6LB and the surname of the CAR operator are sewn up. In order to program your call sign, it is enough to know the telegraph alphabet and understand a little in assembler. Let me tell you that the main commands for this machine are: CALL TIRE, CALL TCHK and CALL PAUZ. The duration of the pause is equal to the duration of the dash, and the dash is actually three dots. And then, according to the rules, there should be 3 pauses between letters, etc. An interval of ten minutes between switching on the machine is set by a conversion factor of three constants TAMH-high byte, TAMM-middle byte, TAML-low byte.

If you change the callsign code and last name, the response time will be slightly different from 10 minutes. You can forcibly start the machine from an external timer by applying a high level signal to the RESET input (switch S2) of the processor for 1,5 - 9 minutes, and for the rest of the time keep the low level on this leg. The frequency of quartz 4 MHz affects the interval between switching on, the frequency and duration of the parcels. You can change these parameters by changing the constants in the program. I give two versions of the assembler code for PIC16c54 and PIC16f84. You can pick up the coefficients and debug the circuit on PIC16f84, and then switch to a cheaper PIC16c54. Good luck. Soon I'm going to make a website for myself and place a few more devices on PIC processors on it. Including reverb, echo repeater, paging and synthesizer for VHF transceiver. I invite you to cooperate for developments based on PIC.

Assembly code for PIC16s54 (DOS encoding)

Assembly code variant for PIC16f84 (DOS encoding)

Author: Oleg, RV6LRC; Publication: N. Bolshakov, rf.atnn.ru

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