Permitted VHF frequencies for radio amateurs and their purpose. VHF frequency plan for amateur radio stations in Russia Permitted VHF frequencies for radio amateurs; their purpose
Pocket radio 144 MHz
The schematic diagram of a simplex radio station with frequency modulation in the 144 MHz range is shown in Fig. 1. A radio station transmitter is assembled on an integrated circuit (IC) DA1 type K538UN3 and microwave transistors VT1, VT2 type 2T371A.
The link on transistor VT1 performs the function of a master oscillator operating in the range of 72...74 MHz, and the link on transistor VT2 is used as a frequency doubler and power amplifier. The radio station uses an electret microphone VM1 type MKE-3 and a whip receiving and transmitting antenna WA1 50 cm long, which cannot be switched off, since the receiving and transmitting frequencies are separated by at least 4 MHz.
Fig.1. Schematic diagram of a simplex radio station with frequency modulation on the 144 MHz range
In receive mode, a super-regenerative detector on the VT3 transistor is used, providing high sensitivity and wide bandwidth. Thanks to this, the master oscillator does not have quartz, which simplifies and reduces the cost of the entire device. Transistor VT3 performs three functions: it amplifies the received signal, generates oscillations at an auxiliary frequency, and selects a low-frequency signal. Preliminary amplification of the low-frequency signal is carried out by a VT4 transistor of type KT3102G, and power amplification is carried out by an IC of type K174UN4A. At the output there is a small-sized speaker BA1 of type 0.025GD1, connected through socket G1, where you can also connect a headphone with a resistance of more than 50 Ohms (the speaker is turned off). The power source for GB1 is a Krona battery or a similar imported 9 V battery. Switches SA1 and SA2 are type PD9-2 or similar. In addition to their main purpose (indicating the “Receiving” and “Transmitting” operating modes), the HL1 and HL2 LEDs are also indicators of the health of the GB1 battery, signaling that it is low and needs to be replaced.
Let's consider the operation of the device in various modes. When switch SA1 is switched to the “Transfer” mode, the red LED HL2 lights up, and a voltage of 9 V is supplied to the DA1 chip and transistors VT1, VT2. The electrical signal of audio frequency, taken from microphone VM1, is supplied to the input of IC DA1, which pre-amplified it. To avoid overload, a dynamic limiter is installed at the output of the microcircuit (elements R4, R5, C7, VD1 and VD2). The C5R3C6 chain is designed to provide stable amplification and eliminate self-excitation of the IC.
A pre-amplified audio frequency signal is supplied to the input of the master oscillator on transistor VT1, which generates a signal with a frequency that can be tuned within 72...74 MHz. Audio frequency voltage changes the dynamic capacitance of transistor VT1, which leads to frequency deviation. To match the output of transistor VT1 and the input of the doubler/power amplifier on VT2, use the chain C11–C14L3.
The amplified frequency-modulated signal of the 144 MHz range is isolated by the L5С17С18 circuit and is fed to the WA1 antenna through the step-down winding L6. Since the radio receiving path is disconnected from the battery, it does not affect the operation of the transmitter. To increase the stability of the generator frequency, a VD3 zener diode is used.
When switch SA1 is switched to the “Receive” mode, the green LED HL1 lights up, and power is supplied to transistors VT3, VT4 and the DA2 chip. The signal received by antenna WA1 is fed to circuit L7C19 and, through winding L8, is fed to a super-regenerative detector on transistor VT3. For normal operation of this stage, the damping frequency must be correctly selected within the range of 100...150 kHz.
Based on the VT3 transistor, there are signals of the following frequencies: received signal, blanking, super-regeneration noise and the transistor’s own noise. If there is no HF signal in the antenna, then a noise is heard in the speaker, reminiscent of the hissing of a primus stove or boiling water. When the correspondent's radio station is turned on, the noise stops completely and his message is clearly audible. This is how the receiver should ideally work, but for this it needs to be carefully configured. The selected low-frequency signal is fed to transistor VT4 and, for further power amplification, from the volume control R18 to the input of the DA2 chip. To adjust the frequency response and eliminate excitation, this microcircuit has appropriate trim elements. The amplified signal is sent to speaker BA1.
Fig.2. Type of printed circuit board
A 2:1 scale view of the printed circuit board is shown in Fig. 2. The board is made from double-sided foil-coated fluoroplastic by any available method. The second side of the printed circuit board serves as a shield and is grounded at two points. The screen eliminates the influence of the operator's hands. The holes in the board are countersunk with a drill. To control the parameters of the radio station, silver-plated contacts K1–K6 are riveted to the board, to which measuring instruments are connected.
Small-sized unified DM type chokes of 10 μH are used as chokes L1, L4, L9. All winding units are wound with silver-plated copper wire with a diameter of 0.8 mm on a mandrel with a diameter of 6 mm. The coils have the following number of turns: L2, L3 – 6; L5 – 3.5; L6 – 2.5; L7 – 2.5; L8 – 3.5. Coil L6 should be placed next to L5, and L8 next to L7. After setup, all circuits along with capacitors should be filled with good quality paraffin to protect moisture and ensure stability.
Any plastic box of suitable size can be used as a housing. To reduce the influence of the inductance of printed tracks on the parameters of high-frequency circuits, the width of these tracks should be at least 3 mm and it is advisable to tin them. Upon completion of the setup, to protect moisture and prevent corrosion, the printed circuit board should be coated with colorless varnish UR-251 (except SA1, SA2, GB1, BA1, BM1). The battery should be secured with bronze clamps (for ease of operation and replacement). At the back of the case, it is necessary to provide a spring clip for carrying the station in a pocket or on a belt.
If the user intends to increase the range of this station, then it needs to be modified. To do this, you should additionally wind 2 turns of PEV-2 wire with a diameter of 0.8 mm over the L6 coil, assemble an additional RF amplifier, and switch the WA1 antenna to the output of the new RF amplifier. In this way, you can increase the power of the station to 1 W.
To set up the station you will need the following devices and instruments: adjustable power supply; field strength meter; LF and HF generators; oscilloscope; tester; lamp voltmeter; 2 Krona batteries (new and half discharged) to test the station in real conditions; a radio receiver capable of receiving signals in the range 144...148 MHz with a graduated scale; frequency meter; equivalent to a 75 ohm antenna.
Checking the operation of the transmitter. Instead of an antenna, connect the equivalent of an antenna to socket K3 - an OMLT0.25 resistor with a resistance of 75 Ohms. Connect the power supply to pin K4, set its voltage to 9 V and turn on SA2. Set switch SA1 to position “1” – “Transmission”. In parallel with switch SA2, turn on the tester to measure current consumption. To be able to regulate the parameters of the circuit, the following adjustment elements should be introduced: instead of R2 - a 1 kOhm trimming resistor; instead of R3 - a 22 kOhm trimming resistor; instead of R6 and R10 - trimming resistors of 47 kOhm; insert a 10 kOhm trimmer into the cut of capacitor C8; Instead of capacitors C10, C11, C12, C14, C17, include trimming capacitors with a capacitance of 2.9...20 pF.
Connect an audio frequency generator to pin K1, and an oscilloscope to pin 8 of DA1; set a signal at the generator output with a frequency of 1 kHz and an amplitude of 200 μV; Use an oscilloscope to observe the shape of the curve - it should be a pure sinusoid. In case of excitation, R2 and R3 should be adjusted. Increase the amplitude of the generator signal to 2 mV. The amplitude of the sinusoid observed on the oscilloscope should increase. If there is distortion in the signal shape, adjust R3 and R5 in the dynamic limiter circuit.
Then they move on to setting up the generator on transistor VT1. The audio frequency generator is turned off, and the oscilloscope is connected to the collector VT1. By adjusting R6 and C12, we achieve a pure sinusoid on the VT1 collector. Having turned off the oscilloscope, connect a frequency meter to the VT1 collector and, by rebuilding C10, check the overlap of the 72...74 MHz range. If necessary, you can compress or stretch the L2 turns. Set the frequency to 72 MHz.
To configure the frequency doubler/power amplifier on the VT2 transistor, connect an oscilloscope to the VT2 collector and use resistor R10 to set half the operating voltage on the VT2 collector, which is checked with a lamp voltmeter. After this, circuit C11C14L3 is adjusted in order to obtain maximum excitation of transistor VT2 and obtain maximum amplitude on circuit L5C17.
To do this, adjust capacitor C17 until maximum amplitude is obtained. Connect an oscilloscope to circuit L6 and adjust R10, C11, C14, C17 again; there should be a pure sine wave on this coil. Place a control radio receiver near the L5С17 circuit and check the transmitter frequency on the scale; it should be equal to 144 MHz.
Instead of an equivalent antenna, include a real antenna. Place the field strength meter at a distance of at least 1 m and again adjust C11, C14, C17, R10 (and, if necessary, R4, C8, C10) to achieve maximum readings of the field strength meter. The current consumption should be about 37 mA.
The next test is from a sound generator connected to point K1. Turn on the control radio receiver and listen to modulation at a frequency of 1 kHz; the sound must be clear. If necessary, adjust R4 to obtain maximum radio volume. When setting up a second transmitter, it must be set to a frequency of 148 MHz. The receiver of the first radio station must be tuned to the same frequency, and the receiver of the second radio station must be tuned to 144 MHz.
To configure the radio receiver, you need to connect a sound generator to pin K6, and an oscilloscope in parallel with speaker BA1. Apply power via switch SA1 to transistors VT3, VT4 and microcircuit DA2. To configure the receiver, you need to install the following adjusting elements: instead of C19, C23, C30 - tuning capacitors 2.9...20 pF; instead of C22 - a variable capacitor up to 50 pF; instead of R13 - a 220 kOhm variable resistor; instead of R14 - by 10 kOhm; instead of R19 - at 51 kOhm. Set the volume control R18 to maximum. Switch the oscilloscope to the collector of transistor VT4. By adjusting resistor R14, achieve half the supply voltage at its collector, which is recorded by the lamp voltmeter. Apply a voltage of 1 kHz 500 µV from the sound generator to contact K6. The oscilloscope on the collector of this transistor should show a pure sine wave, otherwise you need to adjust R14. If, when a 100 µV signal is applied to the VT4 input, 50 mV is obtained at the collector, then this is a completely satisfactory result.
Now you should achieve normal operation of this node together with the DA2 chip. To do this, switch the oscilloscope parallel to head BA1 and adjust R19 and R21 to achieve a pure sine wave on this head; sometimes it is necessary to adjust R22. The voltage on head BA1 should be about 1.5...2 V. After setting up the ULF path, you should proceed to setting up the super-regenerative detector on transistor VT3, and disconnect the sound generator from pin K6; You need to connect an oscilloscope here. Set all the tuning elements of this transistor to the middle position, use potentiometer R15 to set the collector current to about 2 mA; By adjusting the feedback capacitor C23, you should achieve “super noise” in the dynamics, and “goosebumps” should be visible on the oscilloscope screen.
If whistling is mixed with the noise, you should adjust capacitor C23 and change R15. When a steady noise is established in the speaker, you should reduce the supply voltage to 5 V and the noise will appear again. This is how the optimum is found. Typically, setting this cascade at two extreme points of the supply voltage guarantees its normal operation at all others.
Then the generator is connected to pin K3 and the frequency is set to 144 MHz with modulation turned off. By adjusting C19 and C23 it is necessary to achieve voltage resonance; At the same time, the noise in the dynamics will disappear, and “goosebumps” will appear on the oscilloscope screen. Enable modulation. The speaker must have a clear modulation sound, without impurities, otherwise you need to adjust all the elements again. The practice of tuning these cascades shows that the value of the RF voltage supplied to the input of the receiver antenna, at which the “super noise” disappears, is the sensitivity of the radio receiver. When setting up, you need to strive to ensure that the value of this voltage is the smallest, since it is better to increase the communication range by improving the sensitivity of the receiver, and not by increasing the transmitter power, which entails an increased consumption of the capacity of the power supplies.
Having configured the first radio station using a control radio receiver, you should make a second one and after tuning it, you need to check them in interaction with each other. This may require additional adjustments. At the very end of the adjustment work, you should select the resistances of resistors R11, R23: by the glow of the LEDs HL1 and HL2 and their absence, it will be possible to judge the need to replace element GB1. To do this, at 9 V, set the current through the LEDs to no more than 3 mA, then at 5 V they will stop lighting, which means the need to change the battery.
During operation, headphones with a resistance of more than 50 Ohms can be connected to the G1 socket; The speaker is turned off. At the end of the tests, you should turn off the power supply and power the circuit from a real fresh and run-down Krona element. It is quite possible that the adjustment elements will need to be adjusted again.
Upon completion of the setup, replace all tuning elements with permanent ones, fill the board with UR-251 varnish.
Details. Capacitors: C2, C26 – KM-6 0.1 µF; C1, C15, C21, C31, C32 – K50-35 10 µFx16 V; C4 - C8, C16 – KM-6 10 nF; S10, S12, S18, S19 – KT-2 10 pF; C3, C25 – K50-35 47μFx16 V; S24 – K50-35 330 µFx16 V; S28 – K50-35 220 µFx16 V; C39 – K50-35 100 µFx16 V. Resistors OMLT-0.125: R1, R5, R6, R9, R14 – 15 kOhm; R2, R22, R24 – 51 Ohm; R7, R8 – 510 Ohm; R4 – 330 Ohm; R10 – 12 kOhm; R19 – 5.1 kOhm; R17 – 3 kOhm; R16 – 220 kOhm; R13 – 8.2 kOhm; R11, R23 – 2.2 kOhm; R18 – SP3-23 150 kOhm; R13 – SP3-33 470 kOhm.
Semiconductor devices: VD1, VD2 – D310; VD3 – 2C156A; HL1 – AL336V; HL2 – AL336K; VT1–VT3 – 2T371A; VT4 – KT3102G; DA1 – K538UN3; DA2 – K174UN4A.
Switches SA1, SA2 – PD9-2; microphone VM1 – MKE-3; speaker BA1 – 0.025 GD1; battery “Krona” GB1; antenna WA1 – 6 elbows, length 500 mm.
It is no secret that with the advent of mobile phones, the interest of radio amateurs in designing individual means of communication has decreased somewhat. However, there are still areas of activity where it is impossible to do without a conventional simplex radio station. The 144 MHz pocket radio described in the article can be used almost everywhere: during commissioning at an enterprise, for communication with crane operators at construction sites, for hunters, fishermen, tourists or speleologists...
R.N. Balinsky, Kharkov
Radioamator 2005 No. 07
The radio station consists of a main unit, which is mounted on a moving object or in a housing suitable for field conditions, and a speaking tube, which contains AF amplifiers with a microphone and speaker, a switch for receiving and transmitting modes, a tone generator, and a volume control.
The position of these controls on the handset body is designed so that you can operate the radio station with one hand, which is convenient when driving a vehicle.
Radio station characteristics:
1. Range - three channels in the 144 MHz range.
2. Modulation type - FM with a deviation of 3 kHz.
3. Receiver sensitivity with a signal-to-noise ratio of 3:1 - 2 µV.
4. Transmitter power - 4W.
5. Current consumption during transmission - 1A.
6. Receiving current consumption is 50mA.
7. Supply voltage - 12-14V.
The schematic diagram of the main unit is shown in Figure 1. The receiving and transmitting paths are selected separately, this greatly simplifies switching. The transmitter is made on three transistors VT1-VT3. The master oscillator is made using transistor VT1. Its frequency is stabilized by a quartz resonator at 48.2 MHz, and the collector circuit is tuned to the third harmonic of 144.6 MHz. Good results are also obtained with a resonator other than 24 MHz, but starting it at the sixth harmonic is much more difficult. Any other resonator at 48-48.5 MHz is suitable. To receive multiple channels, entered
a switchable circuit for shifting the resonant frequency of the resonator on three switchable coils L1-L3 and capacitor C11. In the process of setting up a radio station by adjusting their inductances, you can get three channels within 200-300 kHz from a frequency of 144.6 MHz.
To ensure the ability to work with more complex radio stations that have a frequency synthesizer, a function has been introduced to adjust the transmitter frequency within small limits using a VD1 varicap. Frequency modulation is performed using another varicap VD2.
This is followed by two power amplification stages, at the output of the latter a 144 MHz loop vibrator is turned on. When switching the receiving and transmitting modes to the output stage, power is supplied constantly, the power of the master oscillator is switched (the output transistors of the transmitter operate without an initial bias and, as a result, in the absence of a signal from the generator, practically do not consume current).
In reception mode, the signal from the antenna through capacitor C16 is supplied to the RF amplifier on the field-effect transistor VT4. In transmit mode, it is protected from overload by a diode limiter. The gain of the cascade is set by tuning
resistor R10. The input and output circuits of this stage are configured to the middle of the received range (middle channel). From the output of the RF frequency converter, the signal is supplied to the frequency converter on microcircuit A1. The K174PS1 microcircuit has a built-in local oscillator, but in this case it is necessary to provide quartz stabilization and use the third harmonic of the resonator, as well as provide a resonance frequency shift and a mode for adjusting the local oscillator frequency, so the local oscillator is made separate on the VT5 transistor.
Its circuit and operation are similar to the master oscillator of the transmitter, but this oscillator has significantly less power. Switching of channels occurs by switching inductances connected in series with the resonator, and adjustment is done by changing the capacitance of the shifting circuit using a varicap VD4. The resonator is taken at 46 MHz, but is also suitable for 23 MHz, if it is possible to start the generator at the sixth harmonic.
At the output of the converter, circuit L12 C26 is turned on, tuned to an IF frequency of 6.5 MHz, the signal from this circuit is supplied to the universal module UPCHZ-2 from the 3-USTST color TV. This module contains a complete amplification and detection path for the FM IF signal, including piezoelectric filters at the input and in the phase-shifting circuit of the frequency detector.
The use of this very affordable module greatly simplifies both the manufacture and configuration of the receiving path. Power is supplied to the receiver only in receive mode. The schematic diagram of the handset is shown in Figure 2. It contains two ultrasonics, the first on VT1 VT2 amplifies the signal coming from the M1 electret microphone (a microphone from an imported handset is used), the second on VT3-VT5 amplifies the signal from the detector of the receiving path and at its output a dynamic sound emitter from the same imported handset is included (and the handset body is also from a handset).
Switch S1 - P2K is not latched; when free, it turns on power to the receiving path, and when pressed, to the transmitting path. SK1 is also without fixation; when pressed, the amplifier on VT1 VT2 turns into a ringing signal generator. Resistor R8 is the volume control.
The handset is connected to the main unit using a seven-pin 2PM18 type connector from military equipment, but you can also use a standard LF connector with 6 connections.
The radio station operates in the ultrashort wave range 144-146 MHz and has a separate receiver and transmitter, which makes it possible to carry out both half-duplex and full-duplex communications. The transmitter uses frequency modulation, which has a number of advantages over amplitude modulation.
The communication range reaches 1-1.2 km when working with such a radio station and can be slightly increased if the correspondent uses a more powerful transmitter and a receiver with increased sensitivity.
The antenna is a quarter-wave rod 47 cm long, but you can also use a flexible wire or high-frequency cable from which the outer braided shielding has been removed.
Scheme. The radio station is assembled on six transistors (two P403 types and four P14 types).
The receiver is made according to a direct amplification circuit with a super-regenerative detector (T1) and two low-frequency amplification stages (T2 and T3) (Fig. 25).
The super-regenerative detector has self-quenching of the auxiliary frequency, carried out by resistance R1 and capacitor C2. The super-regeneration mode is determined by capacitor C3. The oscillatory circuit of the super-regenerator (L1C4) is adjusted by capacitor C4.
The high-frequency generator in the transmitter is made according to a self-excitation circuit on transistor T4, the frequency modulator is on transistors T5 and 76. Frequency modulation is carried out on the base of high-frequency transistor T4. Compared to modulation on the collector or emitter (as well as with grid modulation in tube circuits), in this case the modulator power is required significantly less.
The choice of the operating point of the high-frequency generator is made based on considerations of the constancy of the amplitude of the generated signal with small changes in voltage at the base of the triode. The operating point of the generator is determined by the values of resistances R7, R8, R9. The current consumed by the generator is 12 mA.
Rice. 25. Diagram of a radio station using transistors with frequency modulation of the transmitter.
The frequency deviation in the transmitter is 200 kHz. To do this, you need to change the voltage at the base of the triode within ±0.1-0.15 V. At such voltages based on the triode, the dependence of the generator frequencies on the modulating voltage is almost linear.
The transmitter circuit (L2 C10) is tuned to a frequency of 146 MHz, the receiver circuit (L1 C4) is tuned to a frequency of 144 MHz.
The antenna is connected directly to the base of the T4 triode; it is connected to the receiver circuit (L1 C) through capacitance C1.
Details. Many of the parts used in the radio are similar to those used for the transistor radios described above.
Transformer Tr is wound with wire PEV 0.05; winding I contains 5,000 turns, and winding II contains 2,500 turns. To make a transformer, you can use
Build the frame and plates from the output transformer for the “Sound” hearing aid, which is made on Sh-6 permalloy with a package thickness of 10 mm.
For the manufacture of loop coils L1 and L2, silver-plated copper wire with a diameter of 0.8–1.0 mm is used, which is wound with tension on a ceramic or polystyrene rod with a diameter of 12 mm. Coil L1 contains three turns with a total length of 8 mm, coil L2 contains two turns with a length of 6 mm. The ends of the wire in coils L1 and L2 are firmly fixed to the edges of the rods.
Capacitor C4 is an air tuning capacitor with a capacity of 3 to 10 pF. It can be made in the same way as shown in Fig. 3. C10—ceramic tuning capacitor.
High-frequency chokes Dr1 and Dr2 are wound turn to turn on high-resistance resistances VS-0.25 with PEV 0.1 wire; they contain 40 turns each. Data for all other parts are shown in the diagram in Fig. 25, when choosing them, you should be guided by the considerations noted in the description of previous radio stations.
The insulator for the antenna can be made according to Fig. 4, reducing the indicated dimensions by 2 times.
The radio station uses a high-impedance telephone with a coil resistance of 1000 ohms and a piezoelectric microphone from hearing aids.
The antenna is a pin made of a copper or aluminum tube with a diameter of 4-6 mm and a total length of 47 cm. For communication over short distances (up to several tens of meters), a flexible mounting wire 47 cm long can serve as an antenna.
Design and installation. The radio station along with power supplies is mounted in a flat box measuring 150X70X24 mm. The design of the box is similar to that shown in Fig. 10. The cover is made in the form of a flap that fits into the grooves on the radio body.
In Fig. Figure 26 shows the arrangement of parts in the radio housing. The leads of all parts and transistors are soldered to the pins of the support posts, the design of which is shown in Fig. 12. The supporting insulating struts are attached to the radio body using BF-2 glue.
The Tr transformer is attached to the radio body with a clamp made of an aluminum strip.
The power switch and the switch for switching from receiving to transmitting are located on the side of the box near the power sources. Installation of the radio station must be done carefully and accurately. This especially applies to the installation of high frequency generators. First of all, you need to strive to ensure that the installation wires have a minimum length.
Rice. 26. Internal view of a radio station using transistors with frequency modulation of the transmitter.
You should also shorten the leads of high-frequency transistors to 1 cm. Special care must be taken when soldering these leads. To avoid overheating during soldering, they must be clamped with pliers or tweezers, which in this case act as a heat sink.
Power supplies. To power the radio, two 3-FMTs-20M (“Light”) batteries are used, each of which has a voltage of 2.6 V. These batteries, when installed in the radio housing, are connected to each other in series. Any other small-sized batteries or accumulators with a total voltage of 4.5-6 V can be used as power sources for the radio station.
Due to the fact that the radio station is designed to operate in the amateur VHF range of 144–146 MHz, high-frequency transistors with a maximum generation frequency fa = 140–150 MHz must be selected in the cascades of the supergenerative detector (T1) and generator (T4). For this purpose, from several transistors it is necessary to select those that have the highest maximum generation frequency.
The procedure for setting up a radio station is similar to those described above. Before turning on the radio station, in accordance with the circuit diagram, the correct installation is checked, then the power supplies are turned on and, using the TT-1 tester, the operating mode of the transistors is selected, which is indicated in the diagram in Fig. 25.
After this, you should check the operation of the receiver without connecting an antenna. During normal operation of the receiver, super-regenerative noise will be heard in the phone, which should be uniform over the entire range of received frequencies. A complete absence of noise or a whistle in the phone means an incorrect choice of the super-regenerator operating mode or a malfunction of the low-frequency amplifier. In this case, first of all, it is necessary to check the low-frequency amplifier and, having made sure that it is in good working order, move on to setting up a super-regenerative detector cascade (T1). First, the presence of high-frequency oscillations in the L1C4 circuit is checked. To do this, a milliammeter is used to monitor the change in current in the collector circuit. When coil L is closed, the instrument readings should increase by 1.1-1.3 times. By selecting the values of capacitors C2 and C3, as well as resistance R1, the best operating mode of the super-regenerative detector is achieved. For the same purpose, you can slightly change the voltage on the collector of triode T1 (by sequentially connecting a damping resistance of 1-10 kohms into its collector circuit), and also swap the ends of the connection in the circuit of one of the windings of the transformer Tr.
If the transistor used (for example, type P403) does not operate in super-regenerative mode, it is necessary to do the following: disconnect the end of resistance R1 from the radio body and connect it to the plus of a separate battery (voltage 2-5 V), the minus of which is grounded. The voltage from this battery should be changed by applying it through a potentiometer of 10 koz, so that the emitter current of transistor T1 is about 2-3 mA.
After setting up the receiver is completed, they begin to check the operation of the transmitter. Having checked the operating modes of transistors T4, T5 and T6 in accordance with the voltages indicated in the diagram, we begin to determine the operation of first the low-frequency amplifier (T6 and T5), and then the high-frequency generator (T4). Checking the low-frequency amplifier in the transmitter is similar to checking the low-frequency amplifier in the receiver. A high-impedance telephone is connected to the positive end of the electrolytic capacitor C13 and the radio body. The quality of the amplifier is checked by listening to the words spoken in front of the microphone in the telephone.
The presence of high-frequency oscillations in the oscillatory circuit (L2 C10) is determined in the same way as was done when checking the super-regenerative cascade of the receiver. In the absence of high-frequency oscillations in the L2 C10 circuit, it is necessary to correctly select the operating mode of triode T4, which is achieved by changing the values of resistances R7, R8 and R9, as well as changes within small limits in the voltage of the power source.
Frequency deviation is achieved by changing the modulating voltage applied to the base of transistor T4. To obtain narrowband frequency modulation, the modulating voltage must be several millivolts.
After connecting the antenna, the operation of the radio station is checked with another VHF radio station, whose transmitter is tuned to a frequency of 144 MHz and the receiver to 146 MHz.
My radio station is on 144 MHz
Is it possible to make a station at home that is not inferior to the bourgeois one? (meaning 144 MHz). You decide. In terms of characteristics, Mayak is capable of surpassing bourgeois consumer goods. The MAYAK radio station was widely used in professional VHF radio communications. It is distinguished by high reliability, good technical characteristics and high stability of the main parameters.
The sensitivity of the receiver is 0.4 µV with a signal-to-noise ratio of 12 dB. However, with proper adjustment of the operating modes of the UHF cascades and some adjustment of the spiral resonators, the sensitivity can easily be increased to a value of 0.2 µV and higher. By adding a switchable UHF on the gallium arsenide field-effect transistor AP325A-2 without altering the Mayak input stages, the radio station on the air is no longer inferior to potbelly stoves in sensitivity, and when connecting an antenna amplifier it is superior. The selectivity of the receiver over the adjacent channel is determined by the use of a monolithic quartz filter. In terms of selectivity, noise immunity and overall reliability, the station is superior to many domestic and imported ones. The noise reduction system is not made according to the classical principle of amplifying and detecting the IF signal, however, it provides good quality noise reduction and, when the regulator is brought to the front panel, it responds to the appearance of any weak carrier.
The transmitter power amplifier contains 4 amplification stages, an automatic power control circuit, a low-pass filter, and a receive/transmit switch on pin diodes. From the point of view of reliability and security, the scheme is designed quite well. The output power is 10 watts, but the applied element base makes it possible to obtain an output power of more than 50 watts without altering the circuit. The current consumed by the radio reaches 8A at 13.8 volts and is provided by a modified power supply from the PC/AT.
I tried to bring together all the achievements of radio amateurs and translate them “in metal.” I propose a technique for converting a radio station for use in a mobile-stationary amateur version. Appearance in photo 1.
To obtain a good appearance and ease of operation in amateur radio conditions, the control unit has been mechanically modified. The front panel is milled. The recess contains a printed front panel with protective plexiglass 1 mm thick. It has a 10 k connector for connecting a headset with speaker and microphone or a computer. The use of an electret microphone makes the signal clear and the voice natural. The microphone amplifier is assembled on two KT315s according to the original Mayak circuit and is located in the headset. To connect a computer, a PTT signal, a noise suppressor signal, and a signal for CW manipulation of the power amplifier are output to the connector. When connecting a PC, it becomes possible to work with digital modes of communication, connect DSP filters, programs for a digital tape recorder, beacon, echo repeater, high-quality external ULF, equalizer, use reverberation, etc.
The UHF is assembled according to the scheme of Igor Nechaev (UA3WIA) and Nikolai Lukyanchikov (RA3WEO), published in Radio magazine No. 9, 2000. The tuning technique is also given there.
The S-meter was assembled with minor changes according to the schemes of Igor Nechaev (UA3WIA) published in the magazine “Radio” No. 11 for 2000 and No. 8 for 1998.
The printed circuit board with K174 UR5 is located in the main unit and is shown in the figure, and the K1003PP1 indication chip is installed in the control unit and the location of the elements is visible in the photo.
The front panel also has 12 S-meter LEDs, an indication of the TX mode, UHF on, a switch for two-level change in output power and a maximum power indicator, a volume control, buttons for turning on the standby mode for using the pilot tone, call tone, turning on the UHF and controlling the frequency synthesizer .
The main difficulty when converting a radio station is usually the frequency control device. I used a synthesizer control device made according to the excellent design of E.Yu. Dergaev. UA4NX and allows you to control the frequency of the MAYAK radio station in the range of 144.5-146.0 MHz. A detailed description and firmware are available on the author’s home page http://www.kirov.ru/~ua4nx and on this site (Control of the frequency synthesizer of the “MAYAK” radio station on an AVR microcontroller). In repeater and anti-repeater modes, the transmission frequency is indicated. The program stores 63 channel frequencies and one VFO in non-volatile memory, including repeater spacing +600 kHz, anti-repeater spacing -600 kHz, with a tuning step of 25 kHz. Writing frequencies to each memory cell is guaranteed 100,000 times. In the “SCAN” mode, scanning occurs from memory channels 53 to 63, in the “DUAL” mode, scanning occurs between any memory channel and “VFO”. When the power supply voltage drops, dashes appear on the indicator. When you turn off the power or press the “CLOCK” key, the indicator enters clock mode. Key presses are confirmed by a short, high-pitched beep. For “LOCK” mode in transmit mode, pressing “H” will lock the keyboard. To remove the lock, press “L” in transfer mode.
The controller itself is built into the Control Panel, power supply is +13.8 V. The control buttons are from computer mice with long rods. The indicator is an analogue of NT1611, used in caller IDs. Unfortunately, to work on SSB sections, the firmware needs to be modified.
On the main unit, an IF signal is output through a 10 pF capacitor to the connector for receiving digital, SSB and CW signals through an additional receiver.
The installation of additional boards is visible in the photo.
The radio station has been in use for more than 5 years, worked in the field during the “Valley” expedition and showed high reliability. Many connections have been made with regions 1 and 3 of Russia, the Baltic states, and the Kaliningrad region through repeaters. The maximum communication range in the direct FM channel with a 5/8 antenna at tropo was 611 km ( LY3UV QTH KO14WU). When you are in the radio visibility zone, you can clearly hear the work of the International Space Station repeater on 145,800 kHz FM.
In the future, it is planned to install a “Radio-76” board in the main unit with EMF on both sidebands, CW and work in a package via satellite.
For those who want to experiment with domestic devices and those who prefer to go on the air with hand-made transceivers, I will answer all questions and invite you to the home page for discussion on the forum. Other improvements will also be posted there, the diagram and design of the RS switching unit - radio station, photos and dimensions of the 5/8 “bottle” antenna, sketches of printed circuit boards, because the boards were developed “in pencil” and corrected when drawing on PCB. I believe that creating a modern home radio requires the efforts of various specialists (circuitry, programming, radio communications, antennas, etc.). Therefore, I invite those who wish to unite and express their opinion. I ask the “cool aces” not to be distracted by such trifles.
Details Views: 79693Radio amateurs in Russia, regardless of the category of their radio station, along with the HF bands, are allowed to work in the ultra-short wave (VHF) bands.
The transmitter power of radio stations of the 4th category when operating in the VHF range should not exceed 5 watts, for radio stations of the 3rd and 2nd categories - 10 watts, for radio stations of the 1st category - 50 watts in the range 144-146 MHz and 10 watts in VHF bands above 433 MHz. The transmitter power of amateur radio stations operating in the frequency band 430-433 MHz should not exceed 5 W. At the same time, the operation of amateur radio stations in the frequency band 430-433 MHz in a zone with a radius of 350 km. from the center of Moscow is prohibited.
To conduct experimental radio communications using the Moon as a passive repeater (EME), as well as using the reflection of radio signals from meteor trails (MS), Russian radio amateurs with the 1st qualification category are allowed to use transmitter power up to 500 watts.
VHF frequency plan for amateur radio stations in Russia
| Frequency bands, MHz | Types of radiation | ||||
| 1 cat | 2.3 cat | 4 cat | |||
| 144 MHz band (2 m) | |||||
| 144,035-144,110 | 0,5 | CW (calling frequency 144.050 MHz) | 50 | 10 | 5 |
| 144,110-144,150 | 0,5 | CW, DIGIMODE (narrowband modes; for PSK31 calling frequency 144.138 MHz) | 50 | 10 | 5 |
| 144,165-144,180 | 3,0 | DIGIMODE (all modes), CW | 50 | 10 | 5 |
| 144,180-144,360 | 3,0 | SSB (calling frequencies: 144.200 MHz and 144.300 MHz), CW | 50 | 10 | 5 |
| 144,360-144,400 | 3,0 | DIGIMODE (all modes), CW, SSB | 50 | 10 | 5 |
| 144,400-144,490 | 0,5 | Beacons only (CW and DIGIMODE) | 50 | 10 | 5 |
| 144,500-144,794 | 25,0 | DIGIMODE (all types; calling frequencies: SSTV - 144.500 MHz, RTTY - 144.600 MHz, FAX - 144.700 MHz, ATV - 144.525 and 144.750 MHz), (duplex: 144.630-144.660 MHz transmission, 144.660-144 ,690 MHz reception), ADS | 50 | 10 | 5 |
| 144,794-144,990 | 12,0 | DIGIMODE (APRS - 144.800 MHz) | 50 | 10 | 5 |
| 144,990-145,194 | 12,0 | FM, repeater only, reception, 12.5 kHz step | 50 | 10 | 5 |
| 145,194-145,206 | 12,0 | FM, space communications | 50 | 10 | 5 |
| 145,206-145,594 | 12,0 | FM (calling frequency 145.500 MHz); repeaters of previously recorded messages, 12.5 kHz step | 50 | 10 | 5 |
| 145,594-145,7935 | 12,0 | FM, repeater only, transmission, 12.5 kHz step | 50 | 10 | 5 |
| 145,7935-145,806 | 12,0 | FM (for satellite operation only) | 50 | 10 | 5 |
| 145,806-146,000 | 12,0 | All types (only for work via satellites | 50 | 10 | 5 |
| 430 MHz band (70 cm) | |||||
| 430,000-432,000 | 20,0 | All types | 5 | 5 | 5 |
| 432,025-432,100 | 0,5 | CW (calling frequency 432.050 MHz), DIGIMODE (narrowband modes, calling frequency 432.088 MHz) | 5 | 5 | 5 |
| 432,100-432,400 | 2,7 | CW, SSB (calling frequency 432.200 MHz), DIGIMODE | 5 | 5 | 5 |
| 432,400-432,500 | 0,5 | Beacons only (CW and DIGIMODE) | 5 | 5 | 5 |
| 432,500-433,000 | 12,0 | All types (calling frequencies: APRS -432.500 MHz, RTTY - 432.500 MHz, FAX -432.700 MHz) | 5 | 5 | 5 |
| 433,000-433,400 | 12,0 | 10 | 10 | 5 | |
| 433,400-433,600 | 12,0 | FM (calling frequency 433.500 MHz); SSTV (calling frequency 433.400 MHz) | 10 | 10 | 5 |
| 433,600-434,000 | 25,0 | All types (calling frequencies: RTTY -433.600 MHz, FAX - 433.700 MHz, 433.800 MHz only for ARS), ADS | 10 | 10 | 5 |
| 434,025-434,100 | 0,5 | 10 | 10 | 5 | |
| 434,100-434,600 | 12,0 | All types | 10 | 10 | 5 |
| 434,600-435,000 | 12,0 | FM, repeater only, transmission, 25 kHz step | 10 | 10 | 5 |
| 435,000-440,000 | 20,0 | All modes, via satellites only 435-438 MHz | 10 | 10 | 5 |
| 1296 MHz band (23 cm) | |||||
| 1260,000-1270,000 | 20,0 | All types, work via satellite (Earth-space) | 10 | 10 | 5 |
| 1270,000-1290,994 | 20,0 | All types | 10 | 10 | 5 |
| 1290,994-1291,481 | 12,0 | FM, repeater only, reception, 25 kHz step | 10 | 10 | 5 |
| 1291,481-1296,000 | 150,0 | All types | 10 | 10 | 5 |
| 1296,025-1296,150 | 0,5 | CW, DIGIMODE (narrowband modes) | 10 | 10 | 5 |
| 1296,150-1296,800 | 2,7 | All modes (CW - 1296.200 MHz, FKS441 -1296.370 MHz, SSTV - 1296.500 MHz, RTTY -1296.600 MHz, FAX - 1296.700 MHz) | 10 | 10 | 5 |
| 1296,800-1296,994 | 0,5 | Beacons only (CW and DIGIMODE) | 10 | 10 | 5 |
| 1296,994-1297,490 | 12,0 | FM, repeater only, transmission, 25 kHz step | 10 | 10 | 5 |
| 1297,490-1298,000 | 12,0 | FM, 25 kHz step, calling frequency 1297.500 MHz | 10 | 10 | 5 |
| 1298,000-1300,000 | 150,0 | All types | 10 | 10 | 5 |
| Range 2400 - 2450 MHz | |||||
| 2400-2427 | 150 | 10 | 10 | 5 | |
| 2427-2443 | 10000 | All types (work via satellite), ATV | 10 | 10 | 5 |
| 2443-2450 | 150 | All types (work via satellite) | 10 | 10 | 5 |
| Range 5650 - 5850 MHz | |||||
| 5650-5670 | 0,5 | CW, DIGIMODE (narrowband modes, Earth-to-space), calling frequency 5668.2 MHz | 10 | 10 | 5 |
| 5725-5760 | 150 | DIGIMODE (all types) | 10 | 10 | 5 |
| 5762-5790 | 150 | DIGIMODE (all types) | 10 | 10 | 5 |
| 5790-5850 | 0,5 | CW, DIGIMODE (all modes; satellite communications, space - Earth) | 10 | 10 | 5 |
| Range 10000 - 10500 MHz | |||||
| 10000-10150 | 150 | DIGIMODE (all modes), CW | 10 | 10 | 5 |
| 10150-10250 | 10000 | All types | 10 | 10 | 5 |
| 10250-10350 | 150 | DIGIMODE (all modes), CW | 10 | 10 | 5 |
| 10350-10368 | 150 | All types | 10 | 10 | 5 |
| 10368-10370 | 0,5 | CW,DIGIMODE (narrowband modes), calling frequency 10368.2 MHz | 10 | 10 | 5 |
| 10370-10450 | 10000 | All types | 10 | 10 | 5 |
| 10450-10500 | 20 | All types (satellite communication) | 10 | 10 | 5 |
| Range 24000 - 24250 MHz | |||||
| 24000-24048 | 6000 | All types (satellite communication) | 10 | 10 | 5 |
| 24048-24050 | 0,5 | DIGIMODE (narrowband modes, satellite communications) | 10 | 10 | 5 |
| 24050-24250 | 10000 | All types (calling frequency 24125 MHz) | 10 | 10 | 5 |
| Range 47000 - 47200 MHz | |||||
| 47002-47088 | 6000 | All types | 10 | 10 | 5 |
| 47090-47200 | 10000 | All types | 10 | 10 | 5 |
| Range 76000 - 78000 MHz | |||||
| 76000-77500 | 10000 | All types | 10 | 10 | 5 |
| 77501-78000 | 10000 | All types | 10 | 10 | 5 |
| Range 122250 - 123000 MHz | |||||
| 122251-123000 | 10000 | All types | 10 | 10 | 5 |
| Range 134000 - 141000 MHz | |||||
| 134001-136000 | 10000 | All types | 10 | 10 | 5 |
| 136000-141000 | 10000 | All types | 10 | 10 | 5 |
| Range 241000 - 250000 MHz | |||||
| 241000-248000 | 10000 | All types | 10 | 10 | 5 |
| 248001-250000 | 10000 | All types | 10 | 10 | 5 |
2. Transmissions from amateur stations using repeaters on the VHF bands have priority over other transmissions from amateur stations. Amateur station operators must not interfere with such transmissions.
3. To use repeaters of previously recorded messages, obtaining permission to use radio frequencies or radio frequency channels is not required. The frequency of reception and transmission must be the same. It is recommended to limit such use of RES. The operation of repeaters of previously recorded messages on the frequencies 145.45 and 145.5 MHz is prohibited.
Allocation of frequency bands for experimental radio communications using the Moon as a passive repeater (EME) for amateur radio stations in Russia
| Frequency bands, MHz | Max. signal bandwidth at -6 dB, kHz | Types of radiation and uses (in order of priority) | Power depending on category, W | ||
| 1 cat | 2.3 cat | 4 cat | |||
| 144 MHz band (2 m) | |||||
| 144,035-144,110 | 0,5 | CW (calls without prior arrangement - 144.100 MHz) | 500 | 10 | 5 |
| 144,110-144,150 | 0,5 | DIGIMODE (narrowband modes; for JT65: 144.120-144.150 MHz), CW | 500 | 10 | 5 |
| 144,150-144,165 | 3,0 | SSB, CW | 500 | 10 | 5 |
| 430 MHz band (70 cm) | |||||
| 432,000-432,025 | 0,5 | CW | 500 | 5 | 5 |
| 432,025-432,100 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 5 | 5 |
| 432,100-432,400 | 2,7 | CW, SSB, DIGIMODE | 500 | 5 | 5 |
| 434,000-434,025 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 1296 MHz band (23 cm) | |||||
| 1296,000-1296,150 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| Other VHF bands | |||||
| 2320,000-2320,150 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 5760 - 5762 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 10368 - 10370 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 24048 - 24050 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 47000 - 47002 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 47088 - 47090 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 77500 - 77501 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 122250 - 122251 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 134000 - 134001 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
| 248000 - 248001 | 0,5 | CW, DIGIMODE (narrowband modes) | 500 | 10 | 5 |
Allocation of frequency bands for experimental radio communications using the reflection of radio signals from meteor trails (MS) for amateur radio stations in Russia
