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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Frequency synthesizer control for radio stations Transport and Mayak. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Civil radio communications To work in the 2-meter range, radio amateurs often use the industrial radio stations "Transport" and "Mayak", rebuilt for the amateur range. They have good characteristics of the receiving and transmitting paths and a built-in frequency synthesizer. The node described in this article allows you to fully use the capabilities of this synthesizer. Radio stations "Transport" and "Mayak" have a small (from the point of view of a radio amateur) number of working channels. There are several ways to solve this problem, but not all can be used to repeat at home. Encoders on diodes and switches are very bulky. For example, an 80-channel radio requires about 200 diodes. In encoders based on reversible counters and ROM chips with the ability to scan frequencies and indicate it, the number of ICs approaches three dozen. The use of single-chip computers allows simple means with a minimum of details to solve the problem of converting radio stations into a multi-channel version, as well as to introduce a number of service amenities. The proposed block is designed to control the frequency synthesizer in the radio stations "Transport" and "Mayak", rebuilt to operate within the amateur two-meter range. The version of the ROM firmware worked out by the author allows you to work in the frequency band 144.6 ... 145.8 MHz with a step of 25 kHz. including those with a standard receive/transmit frequency shift for operation via a repeater. The amount of ROM allows, in principle, to implement a control unit with more features. In reality, it can provide: - tuning up / down the frequency of the radio station "Transport" with a step of 12.5 kHz (for "Mayak" the tuning step is 25 kHz); - scanning up/down the entire range; - writing to memory and reading from memory 16 frequency values; - scanning of memory cells; - mode of operation through a repeater with a frequency separation of reception / transmission of 600 kHz at any frequency. In the design described here, the controls already provide for the possibility of expanding the service facilities implemented by the control unit of the radio frequency synthesizer. For their introduction, you only need to install a ROM with a new firmware. The control unit consists of a processor node, a tuning frequency indication circuit and a built-in S-meter. The scheme of the processor part and the frequency indicator is shown in fig. one.
The processor DD1 according to the control program recorded in the ROM chip DD3 generates a frequency code in serial form. This was done in order to reduce the number of connecting wires going to the synthesizer compartment. Through level converters on transistors VT1. VT2 and pins 7 and 9 of the XS1 connector, the processor signals are fed to the serial-to-parallel converter located in the synthesizer. The tuning frequency code (also in serial form) is written to the registers on the DD4 - DD7 microcircuits. Such an inclusion of the IC is somewhat incorrect (K561IR2 are overloaded), but. as practice has shown, it is quite reliable. During the year of operation of a dozen boards (many work around the clock), there was not a single case of failure of the K561IR2. But such an inclusion made it possible to organize a static indication with a minimum of radio interference, which cannot be said about the tested dynamic indication. Seven-segment indicators HG1-HG4 are connected to the registers. To simplify the design, the two most significant bits of the indicator HG5 and HG6 are permanently connected to the +5 V power supply and indicate the number "14". Through the VT7 transistor switch, the frequency display is allowed at the signal of the processor. The unit is controlled by four buttons SB1-SB4 and a PTT to enable transmission mode. Tuning up and down in frequency is carried out by pressing the buttons SB4 "UP" and SB3 "DN", respectively. If you hold them for a long time, the frequency will change with increasing speed. The SB2 "S/S" button is provided for the scanning mode. The proposed algorithm for its operation is to press this button, and then specify how to scan: range up (button "UP"), range down (button "DW") or memory (button SB1 - "M"). If there is a station or interference in the channel, the radio station's squelch is activated. Its voltage (+12 V) is applied to pin 4 of connector XS1 of the control unit, and scanning is suspended for a few seconds. If during this pause you press the "S / S" button, the scanning will be stopped. Scanning can be interrupted at any time by pressing the "S/S" button. Working with the memory will start by pressing the "M" button, then, if it is necessary to read the frequency from the memory cell, then the "UP" button should be pressed, and if written to the memory, then the "DN" button. When working with memory, the frequency indicator displays the number "14" and the number of the memory cell, which can only be increased by pressing the "UP" button in the read from memory mode and decreased by pressing the "DN" button in the recording mode. After selecting the desired memory cell, you need to press the "M" button again, and the desired frequency will be read from the memory or written to it. The mode of operation through the repeater is switched on by pressing the "M" button twice. It is indicated by the HL1 LED. As already mentioned, the control unit incorporates an S-meter. It is made on the DA1 chip. included according to the typical scheme (Fig. 2).
The positional designations of parts in this figure continue the numbering from fig. 1. The signal to the input of the S-meter comes with a strong hold, the frequency will change with increasing speed. The SB2 "S/S" button is provided for the scanning mode. The proposed algorithm for its operation is to press this button, and then specify how to scan: range up (button "UP"), range down (button "DW") or memory (button SB1 - "M"). If there is a station or interference in the channel, the radio station's squelch is activated. Its voltage (+12 V) is applied to pin 4 of connector XS1 of the control unit, and scanning is suspended for a few seconds. If during this pause you press the "S / S" button, the scanning will be stopped. Scanning can be interrupted at any time by pressing the "S/S" button. Working with the memory will start by pressing the "M" button, then, if it is necessary to read the frequency from the memory cell, then the "UP" button should be pressed, and if written to the memory, then the "DN" button. When working with memory, the frequency indicator displays the number "14" and the number of the memory cell, which can only be increased by pressing the "UP" button in the read from memory mode and decreased by pressing the "DN" button in the recording mode. After selecting the desired memory cell, you need to press the "M" button again, and the desired frequency will be read from the memory or written to it. The mode of operation through the repeater is switched on by pressing the "M" button twice. It is indicated by the HL1 LED. As already mentioned, the control unit incorporates an S-meter. It is made on the DA1 chip. included according to the typical scheme (Fig. 2). The positional designations of parts in this figure continue the numbering from fig. 1. The signal to the input of the S-meter comes from pin 5 of the D5 chip (K174XA5) on the receiver board of the Transport radio station. The S-meter circuit shown here can also be used for the Mayak radio station, but the AM path for it will have to be made separately (for example, on the same K174XA5). The control unit is connected to the radio station by eight wires through the XS1 connector (partially its contacts are shown in Fig. 1. and partially - in Fig. 2). the purpose of which is given in table. 1. Pin 2 not listed in the table is connected in parallel with pin 1.
Since the frequency synthesizers of radio stations are controlled by a parallel code, in radio stations of the "Transport" type, a regular serial / parallel input board is used. It is installed in the synthesizer on two stands and has 19 pins on the connector. This board needs to be subjected to the next revision. 1. Replace the two resistors installed on the board with 10 kΩ resistors and connect them not to a common wire, but to a +9 V power source. 2. Cut from the side of the microcircuit installation the track going to pin 19 of the connector. 3. On the opposite side of the board, cut the tracks leading to pins 15 and 16 of the connector. 4. Apply to pin 19 of the connector the signal that was previously connected to pin 15. 5. The signal that went earlier to pin 16, apply to pin 15. For the Mayak radio station, the code converter will need to be made independently according to the scheme shown in fig. 3.
The wiring of the outputs of the board is shown in the diagram in the form of a table for two variants of radio stations of the "Mayak" type. The frequency setting bus designations are taken from the factory documentation. Listing several buses separated by commas in the table (for example, B3, E1, K3, etc.) means that all these buses are connected together and connected to the specified output of the code converter board. It should be noted that there are at least two variants of the frequency synthesizer, which differ both in circuitry and in frequency coding. The easiest way to distinguish them is by the principle of coding channel frequencies - a diode encoder (the variant is conventionally called "Mayak-G") or a ROM encoder K155REZ (option "Mayak-2"). You can also distinguish them by the number of K561IE11 microcircuits on the synthesizer board. If the microcircuit K561IE11 is one, then this is Mayak-2. Power to the serial input board (+9 V) is taken from the voltage regulator of the radio frequency synthesizer board. The control unit is powered by a +5 V voltage stabilizer, made on a KR142EN5A microcircuit, which, in turn, is connected to a +12 V power source of the radio station. Current. consumed by the control unit does not exceed 250 mA. Listings of codes for flashing the ROM are shown in Table. 2 ("Mayak-1"). tab. 3 ("Mayak-2") and tab. 4 ("Transport"). To save space, blocks that contain only the FF code are excluded from the tables, and the corresponding addresses are given at the end of each table.
The control unit is made on a double-sided printed circuit board with dimensions of 233x46 mm. Material - foil fiberglass 1,5 mm thick. The board from the side of the location of the parts is shown in fig. 4, and on the reverse side - in Fig. 5. The location of the elements on the board is shown in fig. 6.
The board is designed to install PKN-125 or PKN-150 buttons. Throttle L1 - DPM-0.1. Oxide capacitor! - K53-14. and C4 - K50-35. All fixed resistors are of the MLT-0.125 type, tuning resistors are SPZ-226. Resistors R3. R4. R8-R14 are installed perpendicular to the board. To reduce the overall mounting height, which is important in the future when manufacturing the front panel, it is better to use the HP 1-4-9M assembly with a resistance of 4.7 ... 10 kOhm instead. Zener diodes VD1. VD2 - in glass cases. Diodes VD3-VD7 are placed under the processor chip or on the opposite side of the board. It is desirable to install the ROM chip (DD3) on a socket (DIP-24). to be able to replace it when upgrading the control program. Indicators HG1 - HG6 are also advisable to install on sockets (DIP 14). Instead of those indicated in the diagram, indicators with a common cathode of a different type can be used. As indicators S-Metpa HL2 - HL12, the LED assembly DD12GWA from Kingbright was used - a green glow. If desired, you can achieve good results by using domestic LEDs of the KIPM02 series. but you will have to tinker with painting their side surfaces and aligning the diodes in height when installed on the board. The 18C48 microprocessor can be replaced with an 80C48 chip from Intel or domestic analogues can be used: KRT816BE48 (35. 39): KR1830BE48: KR1835BE35 (39): KR1850BE35 (39). It is permissible to replace the ROM chip with another one with a memory capacity of 2 kbytes, for example, 2716 or K573RF5. The board provides space for two additional LEDs that can be used for other needs (indication of PLL frequency capture, power, etc.) There are also places for variable resistors (SPZ-4 type) to adjust the volume and squelch threshold. as well as under a small toggle switch (for example, to switch the power level). The control unit board is mounted on five racks outside on the front side of the station (opposite the side where the antenna connector is located). Then it is closed with a decorative panel with four sides, soldered from foil fiberglass. Holes are pre-cut in the panel for indicators, buttons, axes of variable resistors, etc. To fasten the decorative panel, four more threaded racks are used, which are screwed onto the racks that fasten the control unit board to the radio station. The code converter for the radio station "Mayak" is assembled on a printed circuit board measuring 74x19 mm (Fig. 7) from foil-clad fiberglass 1,5 mm thick. Before installing the converter board in the radio synthesizer, you must make sure that the synthesizer board has all the pins of the connector for connecting it. Otherwise, you need to solder the missing pins. A serial input board is attached to them, which is fixed on top with two more racks, to which the screen is then attached. In the radio station "Transport" clock pulses and data pulses are supplied, as follows from the table. 1. on the 1st and 2nd pins of the regular serial input board. The control unit is configured in the following sequence. After turning on the unit and passing the reset pulse, the splash screen - "14 ucn" is displayed for several seconds. followed by the current frequency, for example "145500". If this does not happen, it is necessary to carefully check the installation (especially the "processor - register - ROM" connection and their serviceability). The reason sometimes happens in the registers DD4 - DD7. Since they are written sequentially, if the DD5-DD7 are working, but the DD4 register is faulty, the display will still not work, since the data will not pass through it. Data is overwritten in the registers during a frequency change, as well as when the transmission mode is turned on. Therefore, you can check the presence of data pulses at pin 7 and synchronization pulses at pin 9 of the DD4 chip with an oscilloscope by switching the unit to transmission mode or cycling the frequency. When changing the frequency up or down by one channel, there should be no channel "jumping" effect, otherwise the clock frequency should be reduced by using a choke L1 with a larger inductance or capacitors C2 and C3 with a larger capacitance. By selecting the resistor R6, such a noise suppressor threshold is set. so that when you stop the scan mode in the dynamic head, some signal is always heard. The S-meter is tuned with a trimming resistor R18. achieving at a minimum level of the ignition signal of the LED HL2. and resistor R20 - ignition NIH at the maximum signal level. The S-meter characteristic is usually non-linear. Here you can experiment by installing a larger capacitor C6 (up to 4,7 ... 10 microfarads). Naturally, it is necessary to refine the S-meter adjustments each time with trimming resistors R18 and R20. With careful installation and serviceable parts, no other adjustment is required. Short circuits and breaks in the processor part are unacceptable, since it is extremely difficult to detect them. To increase the brightness of the indicators, it is recommended to set the supply voltage +5 ... 5,1 V on the control unit board (in this case, the voltage drop on the connecting wires should be taken into account) using diodes that are included in the open circuit connecting the middle output of the KR142EN5A microcircuit with a common wire . But this method has a drawback - you will have to isolate the KR142EN5A from the body of the radio station. The best option is to use imported indicators, for example, the same company Kingbright - SC04-11GWA. The author would like to thank RW6HRY33 for providing materials and idea, as well as UA9ULT and RA9UMC for valuable advice and participation in design discussions. ROM firmware files: mayak1.bin ("Mayak-1"), mayak2.bin ("Mayak-2"). transp.bin ("Transport"). Author: V.Latyshev (RA9UCN), marinsk@kuzbass.net
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