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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Voice S-meter. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Civil radio communications The device described in this article was designed to automatically "voice" information about the signal strength of the radio station when working through a repeater. It is assembled on the basis of a Chinese-made desktop "talking" clock. The ideas used in this device can also be used in other designs: in devices that make it easier for radio amateurs with partial or complete loss of vision to work on the air, in various answering machines that “voice” inform the user (for example, when asked by phone) about a remote object and so on. When the repeater is turned on, the sensitivity of its receiving path usually decreases somewhat due to the influence of its own transmitter. For this reason, the signal strength of the remote radio station may be sufficient to open the repeater, but insufficient for correspondent calls. As a result, a situation is often observed when the remote operator continuously "pulls" the repeater, trying to figure out why no one is answering him. In this case, only operators of other radio stations can give an objective assessment of the level of its signal. If the repeater is supplemented with an automatic S-meter with "voice" indication, then such an assessment can be obtained even at the moment when there is not a single correspondent in the repeater channel. It is useful to install a similar device in a conventional simplex radio station. An automatic S-meter will also make it easier to tune the antenna, for example, optimizing its matching with the feeder, removing the radiation pattern. A radio station at a required distance equipped with such an S-meter. will be able to automatically transmit objective information about the level of the received signal to the operator. Not superfluous for the repeater when it is turned on will be information about the current time. For the manufacture of such devices, you can use a cheap and widespread speech synthesizer, which is in the "TALKING CLOCK" ("talking clock") made in China. If, for example, when the repeater is turned on, it is ensured through its control system that the “Start” clock button is “pressed”, and the sound signal generated in the clock is applied to the modulator of the repeater’s transmitting path, then it will report the communication time. But much more opportunities are provided by using the "RESET" clock button. It resets the processor and starts the time setting cycle. If the analog parameters of the system (in our example, the level of the received signal) are converted into pulses, and these pulses are used in the clock as control signals for setting the time, then reading the clock readings at the end of this cycle will allow these parameters to be "voiced" In one cycle after pressing the "RESET" button, you can read either two parameters with a maximum recorded value of 24 and 60 units (hours and minutes, respectively), or one parameter with a maximum recorded with a value of 1440 units (24x60).In the latter case, however, it is more difficult to quickly interpret the data "in the mind" (without a calculator). It should be noted that due to the built-in anti-bounce system, the speed of setting hours and minutes is limited from above - the clock frequency of the pulse shaper device should not exceed 15 Hz. As a result, the counting time on the minute channel to implement the entire scale of 60 units will take at least four seconds. We also note that after pressing the "RESET" button, setting the time using the "hours" and "minutes" buttons is possible only after a certain time - about one second. A few words about the internal content of the "talking" clock. The search for points on the board that are used for docking with other components of the device (control inputs, output of the generated audio signal) will have to be approached creatively. The thing is. that the two watches used by the author, despite the same appearance, had printed circuit boards that differed from each other. The circuits associated with the control buttons and with the output of sound information are subject to refinement in the clock. The control buttons work by shorting to a common wire (Fig. 1). The common wire in the clock is connected to the negative terminal of the battery.
The output transistor of the sound channel is located near the place where the wires from the dynamic head are connected to the board. With an avometer turned on in the resistance measurement mode, we find the outputs of the emitter of the transistor (it is connected to a common wire) and its collector (it is connected to one of the outputs of the dynamic head). The remaining output of the transistor is the base. After pressing the "Start" button, a bias is supplied to the base circuit of this transistor from the BIS, which brings it to class A mode. and an audio frequency voltage. "Voice" information from the base circuit is fed to the microphone input of the radio station. On fig. Figure 2 shows a schematic diagram of an additional node that provides automatic transmission of the current time on the air.
The transistor key (VT2) with a logic level of 1 from the noise suppressor (ShP) of the receiving path turns on the voice announcement mode of the time (simulating pressing the "Start" button). Transistor VT1 of the clock in this mode is used as a key that turns on the transmission. The R3C2 circuit smooths out the control current ripple and provides some (2 ... 3 V) voltage at the lower output of the resistor R3 according to the circuit. It can, if necessary, be used to block (with a key on the transistor VT3) the microphone for the duration of the transmission of time information. The transmitter control current can be up to 15 mA. which is enough, for example, to turn on a radio station of the R-838 type ("Viola", "Kremnica"). The time transmission mode is switched on by switch SA1. In the position indicated on the diagram, the clock and the transceiver work independently. This service convenience can easily be made to be enabled only upon over-the-air request (for example, by the requesting radio transmitting a tone signal of a certain frequency). The device, the schematic diagram of which is shown in fig. 3 makes it possible to generate, using such a clock, "voice" information about the signal level of the received radio station.
Clock pulses with a frequency of 1 Hz from the output of the generator on the inverters DD1.1 and DD1.2 through the buffer element DD1.3 are fed to the input of the binary counter DD2. The binary code at its output is decoded by the D03 chip. which controls the inclusion of "RESET" (0th cycle), creates a pause for the time of "resuscitation" of the LSI (1st cycle), enables the operation of the VCO on DD4 (2-5th cycles), turns on the transmission of the transceiver (6-15 -th cycle) and, finally, resets the counter to 0, which ends the working cycle of measuring and issuing a report on signal strength. And it begins with the opening of the silo logic 0, from which the count is allowed through the VD2 diode. If the SHP is open for less than four seconds, the decoder does not have time to "catch" the permission of the counter and the latter is reset to zero. The device does not complete the duty cycle, so the transceiver does not transmit. If the operator had the patience to keep the radio station button pressed for five seconds or more (up to 9 s), then the decoder through the diodes VD1, VD7-VD16 supports the operation of the counter already in the absence of 0 with the SR. Information about the number of pulses sent to the "MIN" button per hour is transmitted on the air. For example, the message "0 hours 35 minutes" informs that the signal strength is 35 conventional units. The message is repeated twice. The transmission duration is determined by the number of diodes VD7-VD16. The number of pulses that have passed through the DD1.4 inverter from the VCO per hour is proportional to the control voltage coming from the S-meter on the K174XA6 chip, which is included according to the typical circuit in front of the IF limiter amplifier. Since the voltage of the S-meter in the absence of a signal at the input of the transceiver is approximately 0.2 ... 0.3 V, and the VCO begins to work linearly from 0,6 ... 0.7 V. A trimming resistor R174 is included in the negative power bus K6XA7. By adjusting it, the voltage of the S-meter is shifted by 0.5 V. One more nuance. Since the current 0 at the inputs R of the DD2 microcircuit, with its support from the decoder, passes through two diodes, then VD1 must be germanium. Unused inverters DD1.5 and DD1.6 can be used in SHP and TX circuits. if the transceiver control logic differs from that shown in the diagram. In the author's device, pure ether with a forcedly open SHP gives a report of 3 - 5 units ("minutes"), and the saturation of the S-meter is announced in 55 - 57 minutes. Level S=6 already gives ten impulses. S = 7 - 20. S = 8 - 30. S = 9 - 40. from 40 to 55 - "pluses" (S signal level is more than 9). These values can be changed by selecting R4 elements. R7 and C10. In the IF path after the limiting amplifier, you can put a simple direct conversion receiver with a local oscillator on a quartz resonator or take a local oscillator signal from a synthesizer with a pulse shaper and a divider by 100. The signal from the output of the divider will set the "clock" values. Then, apart from the S-meter report. a message about the frequency deviation will be broadcast (up to a value of 2.4 kHz with an accuracy of 100 Hz). In this case, the message "5 hours 42 minutes" means that DF = 0,5 kHz, the signal strength is 42 units. This is already a whole measuring station! Diodes VD1 and VD2 can be eliminated if pins 2 and 3 of DD2 are disconnected, and the signals "0" SHP and "0" TX are applied to these inputs separately. It should be borne in mind that the amplitude of these signals should not exceed 5.5 V. Since the supply of a larger voltage is not allowed either for the inputs of DD2 or for the outputs of DD3. This is how such a seemingly banal thing as "talking clock" was found to be used. Author: I. Vakhreev (RW4HFN)
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