Radio microphones on transistors. Radio amateur constructions and sale of radio equipment Varicap frequency modulation
The 3579.5 kHz beacon was made from the widely used television quartz for the NTSC system. It was taken as a basis (the author honestly admits this) a scheme of a telegraph transmitter, amazing in its simplicity, taken. The scheme is very simple, efficient and stable in operation:
The radio beacon is assembled on an ordinary circuit board purchased at a local radio store for 40 rubles and placed in a standard purchased silumin box measuring 110 * 60 * 30 mm. Attached to the side is a PL-type connector, power and fan toggle switches, terminals " + " And " – ". From above, to the main body, a cooler is placed on thermal paste, consisting of an aluminum radiator and a standard 50 mm processor fan.
Here's what the finished design looks like:
At the top right, in the 3rd photo, a radiator is visible, which removes excess heat from the 74HC240 master oscillator chip, because it heats up quite noticeably.
The "brain" of this design is the Atmel ATtiny2313 microcontroller. Here, he is entrusted with a rather simple task: switching the intermediate stage on the 74HC240 chip (PTT signal with a dash). At the moment, this radio beacon is programmed (or as the programmers say - hard-skinned) the line "VVV VVV VVV BEACON DE UA0LTB 10WATT ANT DIPOLE QTH LOC PN53XC VLADIVOSTOK RUSSIA". After that, the beacon gives a "Press" signal for 3 seconds, pauses for a few seconds and everything repeats. This makes it easy to recognize the beacon signal on the air. The firmware is written entirely in C and occupies about 1.5 Kbytes in the microcontroller's memory.
Here are a couple of videos about this beacon, I hope that they will seem interesting to my readers.
Checking a beacon at home or a light bulb is the best load:
We listen to the radio beacon on the Yaesu FT-450D at the dacha near UA0LGC, the distance is 25 km:
And here is the C project for Atmel AVR Studio 4. You can use the sources of this project without restrictions. The only condition - be sure to indicate the source.
Here it is necessary to say a few words about this project. It was made in those distant happy times (just kidding), when you could still buy AT90S2313 microcontrollers in the store. Then it became impossible to buy them, my stocks of 90S2313 gradually sold out and ended, and I was lazy to rewrite the project under ATtiny2313. Therefore, I applied this, if I may say so, feint with the ears: I applied tiny2313 in 90S2313 mode. To do this, before flashing, I explain to the controller that it is a real tiny2313, and after the firmware is finished, that it is now 90S2313. Therefore, if you are going to recompile this project and flash controllers for his beacon, then you should pay attention that two additional files are placed in the project folder: "flash.bat" - this is what you need to run to upload the firmware to the controller; in it you will need to write the path to the flasher (I use PonyProg), and in the file "flash.e2s" - the path to the firmware itself (*.hex). Just in case, let me remind you that tiny2313 firmware, like 90S2313, kills tiny, so you need to sew it exactly like tiny, and after flashing, switch it to 90S2313 mode.
If you have a real AT90S2313, then you are a happy person: you don’t need to do any manipulations with fuses and there is much less crap with 90S2313 (according to experience). Just pour the HEX file into the controller and that's it.
Achieved results in audibility. Despite the relatively low power of this beacon (10 W), when used as a transmitting antenna of the "Inverted V" type, it is very well heard on the telescopic antenna of the Tecsun PL-600 receiver throughout the Primorsky Territory. When using an antenna of the "Inverted V" type as a receiving signal, the beacon reaches 59 + 40 at night throughout the region! We heard this beacon at 59 even in Japan, in the port of Toyama (distance 840 km). For this I express my gratitude to Victor, RU0LE (ex UA0LPR).
Interesting features of the propagation of radio waves in the 3.5 MHz band, noticed thanks to this beacon. To evaluate these features, I connected this beacon to the "Inverted V" antenna and went for a walk around the neighborhood with a Vertex VX-7R portable (fortunately, there is HF and a fairly good sensitivity - 3 microvolts). In general, my observations are as follows:
1. I was surprised by the absolutely even audibility, without any interference minima and maxima there, so characteristic of VHF. You go to yourself, look at the scoreboard of the portable device - well, sometimes the signal will grow by 1 point, after 20 meters it will also smoothly fall by 1 point, the signal changes are almost not noticeable. Long wavelength, however.
2. When the portable is in your pocket, you can hardly hear anything, even at short distances from home (on VHF, the audibility does not depend on whether the station is in your pocket or in your hand). But as soon as you take it out of your pocket and raise it above your head, the audibility becomes very good. This is apparently due to large losses in the human body, which is a dielectric with very high losses at HF frequencies.
3. St O and then lower it to the level of the chest or abdomen - audibility sharply worsens (on VHF, the height of the station above the ground has little effect on reception). This is due to the fact that at frequencies of about 3.5 MHz the wave exists practically only in the form of vertical polarization and the losses directly near the ground are very high.
P.S. Strange as it may seem, the original datasheet for the IRF510 does not contain its pinout. And it's pretty hard to find it on the internet. That's why I'm posting it here. So, if you take the transistor with the flange away from you, the inscription on the case towards you, feet down, then from left to right:
1. G - Shutter
2. D - Drain (connected to flange)
3. S - Source
Vadim, UAØLTB
Vladivostok
2009
antennas and radio sports, radio amateurs often use a low-power transmitter,so-called beacon.
"Beacon" is usually located at a distance of several tens or hundreds of meters from the place of adjustment work.
Since such work usually takes a long time,
The transmitter must be equipped with an independent power supply and provide a stable signal in terms of frequency and level during this time.
The scheme of such a transmitter is shown in fig. 1.
It consists of a master oscillator, a frequency multiplier, an output stage, a modulator, and a modulating signal generator.
The device is powered by a battery of galvanic cells or batteries with a total voltage of 8..9.5 V.
The power supply to the generators is supplied through a voltage regulator on the DA1 chip.
The master oscillator is assembled on a transistor VT1 according to the "capacitive three-point" scheme with quartz frequency stabilization.
The ZQ1 resonator operates on the third harmonic, and its frequency can be in the range of 48 ..48.66 MHz.
A frequency tripler is assembled on the transistor VT2.
The transistor operates with a cutoff of the collector current, its optimal mode is set by the tuning resistor R5.
The third harmonic of the master oscillator signal (in the frequency band 144 ... 146 MHz) is selected by the L2C5 circuit and, from part of the turns of the L2 coil, enters the output stage, the transistor VT3.
The L3C11 circuit, also tuned to this frequency, is included in the collector circuit of the transistor VT3.
From the outlet of the coil L3, the transmitter signal through the capacitor C 12 is fed to the antenna socket XW1.
A rectangular pulse generator with an operating frequency of about 1 kHz is assembled on the DD1 chip, and a modulator on the VT4 transistor.
The output stage of the transmitter is powered through the resistor R8 and the transistor VT4. By changing the supply voltage of this stage, you can change the output power level.
This adjustment is implemented using a variable resistor R9.
If the switch SA1 ("Modulation") is closed, then the output of the microcircuit elements DD1.3, DD1.4 and, accordingly, the resistor R9 will have a stable constant voltage. By changing the voltage at the base of the transistor VT4 with a variable resistor R9, the output power level of the signal is changed, while the signal will be emitted continuously.
In position SA1, shown in the diagram, the rectangular pulse generator is turned on.
The output stage of the transmitter is powered by a pulsed voltage and the pulse modulation mode will be implemented.
A continuous transmitter signal can be received by a CW receiver, and a pulse modulated signal can also be received by an AM receiver.
Almost all parts of the device are placed on a printed circuit board made of double-sided foil fiberglass, a sketch of which is shown in Fig. 2.
The second side of the board is left metallized and connected in several places along the edge of the board with a common wire of the first side.
The following types of parts are used in the transmitter: tuning capacitors - KT4-25, KT4-35, constants - KM, KLS. K10-17, oxide - K50-16, K50-35.
Fixed resistors - MLT, S2-33; tuning resistors - SPZ-19; variable - SPO, SP4-1. Transistor VT1 can be replaced with KT316A; VT2 - on KT363B; VT3 - on KT368B.
The DD1 chip can be replaced with K564LA7, DA1 - with any similar low-power integrated stabilizer of the 78xx series.
Switches SA1, SA2 - any small-sized. It is possible to use resistor R9 with a switch, for example, type SPZ-4vM.
Accordingly, the need for SA2 is eliminated.
Jack XW1 - any high-frequency small-sized. Quartz resonator ZQ1 - harmonic for the above frequencies or 16000 .. 16220 kHz (first harmonic) in a small-sized version.
It is advisable to pay attention so that the frequency of the device does not fall on the calling channels of the 144 MHz range.
The inductor L1 is wound with PEV-2 0.4 wire on a mandrel with a diameter of 4 mm and contains 13 turns with a tap from the 4th turn. Coils L2, L3 are wound with the same wire on a mandrel with a diameter of 3.5 mm and contain 6 turns each with a tap from the 1st and 2.5th turns, respectively.
The conclusions of the parts before soldering are shortened to a minimum length.
The board, together with the power supply, is placed in a rectangular metal case measuring 104x64x25 mm.
On the short side wall of the housing, next to the inductor L3, a socket XW1 is installed, switches SA1 and SA2 are installed on the same side.
The variable resistor R9 is fixed directly on the front side of the case through a hole in the board.
Setting up the transmitter begins with a master oscillator.
Capacitor C2 achieves stable generation at the frequency of the quartz resonator.
If the generator will operate at other frequencies, then the capacitance of the capacitor C3 must be reduced, but if the generator is not excited, then the capacitance C3 should be increased.
Then, with capacitors C5 and C11, the corresponding circuits are tuned to the frequency of the output signal, and with a tuned resistor R5, the operating mode of the frequency tripler is set, at which the maximum of the third harmonic signal is obtained. The signal is controlled by a high-frequency oscilloscope with an input impedance of 50 ohms connected to the output of the device.
Trimmer resistor R10 sets the minimum output level that can be obtained at the output of the device.
If desired, the variable resistor R9 can be provided with a graduated scale.
In the author's version of the transmitter, the output power level can be adjusted from 0.01 to 2 mW.
The beacon consumes 9 mA in continuous signal mode and 7 mA in pulse modulation mode.
If a battery is used to power the device, then to charge it, it is advisable to install any small-sized socket on the case and additionally introduce a diode and a resistor into the circuit (the XS1VD1R11 circuit in Fig. 1 is shown by a dotted line). DC voltage 12 V.
VHF BEACON
Igor NECHAYEV (UA3WIA)
To test and tune various VHF equipment and antennas, radio amateurs often use a low-power transmitter, the so-called "beacon". "Beacon" is usually located at a distance of several tens or hundreds of meters from the place of adjustment work. Since such work usually takes a long time, the transmitter must be equipped with an autonomous power source and provide a stable signal in terms of frequency and level during this time.
The scheme of such a transmitter is shown in fig. 1. It consists of a master oscillator, a frequency multiplier, an output stage, a modulator, and a modulating signal generator. The device is powered by a battery of galvanic cells or batteries with a total voltage of 8 ... 9.5 V. The supply voltage to the generators is supplied through a voltage regulator on the DA1 chip. The master oscillator is assembled on a transistor VT1 according to the "capacitive three-point" scheme with quartz frequency stabilization. The ZQ1 resonator operates on the third harmonic, and its frequency can be in the range of 48...48.66 MHz.
Rice. 1
A frequency tripler is assembled on the transistor VT2. The transistor operates with a cutoff of the collector current, its optimal mode is set by the tuning resistor R5. The third harmonic of the master oscillator signal (in the frequency band 144 ... 146 MHz) is selected by the L2C5 circuit and, from part of the turns of the L2 coil, enters the output stage, the transistor VT3. The L3C11 circuit, also tuned to this frequency, is included in the collector circuit of the transistor VT3. From the tap of the coil L3, the transmitter signal through the capacitor C12 is fed to the antenna socket XW1.
A rectangular pulse generator with an operating frequency of about 1 kHz is assembled on the DD1 chip, and a modulator on the VT4 transistor. The output stage of the transmitter is powered through the resistor R8 and the transistor VT4. By changing the supply voltage of this stage, you can change the output power level. This adjustment is implemented using a variable resistor R9. If the switch SA1 ("Modulation") is closed, then the output of the microcircuit elements DD1.3, DD1.4 and, accordingly, the resistor R9 will have a stable constant voltage. By changing the voltage at the base of the transistor VT4 with a variable resistor R9, the output power level of the signal is changed, while the signal will be emitted continuously. In position SA1, shown in the diagram, the rectangular pulse generator is turned on. The output stage of the transmitter is powered by a pulsed voltage and the pulse modulation mode will be implemented. A continuous transmitter signal can be received by a CW receiver, and a pulse modulated signal can also be received by an AM receiver.
Almost all parts of the device are placed on a printed circuit board made of double-sided foil-coated fiberglass-lite, a sketch of which is shown in Fig. 2. The second side of the board is left metallized and connected in several places along the edge of the board with a common wire of the first side.
Rice. 2
The following types of parts are used in the transmitter: trimmer capacitors - KT4-25, KT4-35; permanent - KM, KLS, K10-17; oxide - K50-16, K50-35. Fixed resistors - MLT, S2-33; tuning resistors - SPZ-19; variable - SPO, SP4-1. Transistor VT1 can be replaced with KT316A; VT2 - on KT363B; VT3 - on KT368B. The DD1 chip can be replaced with K564LA7, DA1 - with any similar low-power integrated stabilizer of the 78xx series. Switches SA1, SA2 - any small-sized. It is possible to use resistor R9 with a switch, for example, type SPZ-4vM. Accordingly, the need for SA2 is eliminated. Jack XW1 - any high-frequency small-sized. Quartz resonator ZQ1 - harmonic for the above frequencies or 16000 ... 16220 kHz (first harmonic) in a small-sized version. It is advisable to pay attention so that the frequency of the device does not fall on the calling channels of the 144 MHz range.
The inductor L1 is wound with PEV-2 0.4 wire on a mandrel with a diameter of 4 mm and contains 13 turns with a tap from the 4th turn. Coils L2, L3 are wound with the same wire on a mandrel with a diameter of 3.5 mm and contain 6 turns each with a tap from the 1st and 2.5th turn, respectively.
The conclusions of the parts before soldering are shortened to a minimum length.
The board, together with the power supply, is placed in a rectangular metal case measuring 104x64x25 mm. On the short side wall of the housing, next to the inductor L3, a socket XW1 is installed, switches SA1 and SA2 are installed on the same side. The variable resistor R9 is fixed directly on the front side of the case through a hole in the board.
Setting up the transmitter begins with a master oscillator. Capacitor C2 achieves stable generation at the frequency of the quartz resonator. If the generator will operate at other frequencies, then the capacitance of the capacitor C3 must be reduced, but if the generator is not excited, then the capacitance C3 should be increased. Then, with capacitors C5 and C11, the corresponding circuits are tuned to the frequency of the output signal, and the tuning resistor R5 sets the operating mode of the frequency tripler, at which the maximum of the third harmonic signal is obtained. The signal is controlled by a high-frequency oscilloscope with an input impedance of 50 ohms connected to the output of the device.
Trimmer resistor R10 sets the minimum output level that can be obtained at the output of the device. If desired, the variable resistor R9 can be provided with a graduated scale. In the author's version of the transmitter, the output power level can be adjusted from 0.01 to 2 mW.
If the pulse modulation mode is not needed, the circuit can be simplified by excluding the elements DD1, R4, C9, SA1, and the left output of the variable resistor R9 according to the circuit can be connected to the output of the DA1 microcircuit.
The "beacon" consumes a current of 9 mA in the continuous signal mode and 7 mA in the pulse modulation mode. If a battery is used to power the device, then to charge it, it is advisable to install any small-sized socket on the case and additionally introduce a diode and a resistor into the circuit (the XS1VD1R11 chain in Fig. 1 is shown by a dotted line). The resistance of the resistor R11 is selected in such a way as to provide the rated current for charging the battery from a constant voltage source of 12 V.
VHF BEACON ON 430 MHz AND 144 MHz 
Figure 1 shows a generator for the 430-440 MHz range. In fact, it is a local oscillator (generator). The generator operates on the third mechanical harmonic of a Pe1 quartz resonator. A signal with a frequency of 432 MHz is extracted using a bandpass filter. , 2-1.5 mm. The gap between the line and the board is about 1 mm. You should pay more attention to the quality of soldering the line to the "ground". Considering the high thermal conductivity of copper foil, it is better to solder with a sufficiently powerful soldering iron of 90-100 W. As experience has shown, resonators have good rigidity.
Another scheme of a simple beacon but already at 144 MHz is presented below.
The generator is made on a field-effect transistor, instead of a quartz resonator at a frequency of 12 MHz, you can also use resonators for any subhormonic frequency of 144 MHz. In this case, some correction of the capacitance of capacitors C1 and C2 may be required. quarter-wave resonators, which are folded on the board into a compact design in the form of a "snake" or the letter "U" to reduce the size. The resonators are made of silver-plated wire 0.8 mm, the height above the board is 2.5 mm. As the line height decreases, the scattering field decreases, but the quality factor also inevitably drops. within large limits. The wire diameter can also be changed within 0.8-1 mm.
144 MHz radio beacon
It was made third in a row, but, unlike beacons at 430 and 1200 MHz, it was made according to the classical (non-synthesizer) scheme, with quartz frequency multiplication and on ordinary elements (not SMD). This approach, although somewhat "old", made it possible to obtain the most economical and simple design of all. In addition, the use of conventional (not SMD) parts made it possible to use an ordinary circuit board and refuse to draw and etch a printed circuit board specifically for it, which, of course, affected the cost and speed of manufacturing this beacon.
But this approach has its drawbacks, I will list them here:
1) Low frequency stability. If in a circuit with a synthesizer the frequency stability is determined mainly by the stability of the reference oscillator operating at a low (usually from 4.5 to 15 MHz) frequency, then in the circuit with multiplication - the frequency stability of the quartz generating at a frequency that is only several times less than the working one. In this design, the frequency of quartz generation is 72 MHz. Because of this, the frequency of this beacon can float within plus / minus 1-2 kHz, depending on the humidity of the surrounding air and the temperature inside the case;
2) Difficulties in obtaining normal frequency deviation. Despite the fact that the master oscillator operates at a frequency of 72 MHz, it turned out to be a problem to obtain normal deviation. Probably, this is somehow connected with the quartz switching circuit - I know that there is a series and parallel resonance, and at some of these resonances it can be difficult to obtain a normal deviation. To be honest, I don’t know much about this and I ask my dear readers to correct me if I messed up something here;
3) In pursuit of obtaining a normal frequency deviation, I overestimated the capacitance of one of the isolation capacitors (set 470 uF, but in reality it was necessary 100 times less), which a few days later was discovered in the form of an unpleasant effect of "crying" or "meowing" frequency during modulation. But, fortunately, it is noticeable only in SSB and CW modes, in FM it is absolutely imperceptible.
But the relative simplicity of the circuit and, as a result, a lot of free space inside the case, made it possible to equip this beacon with additional functions for controlling the output power and the presence of modulation, as well as install a microphone inside. Now, in addition, you can use this beacon to control the premises - for example, to determine when a child woke up or just as a wiretap (at this point I wave my hand in greeting to my favorite site vrtp.ru).
Brief table of beacon parameters
Working frequency - 145.175 MHz
Power-80 or 400mW
Generator type - Quartz
Type of m/s synthesizer ----
Output Stage-2SC2053
The radio beacon is assembled on an ordinary circuit board purchased at a local radio store for 40 rubles and placed in a standard purchased silumin box measuring 110 * 60 * 30 mm. Attached to the side is a BNC-female connector, toggle switches for power (power), modulation type selection (beacon / microphone / off) and control, indicator LEDs for the presence of modulation and output power, terminals "+" and "-".
The "brain" of this design is the Atmel ATtiny2313 microcontroller. Here the task is assigned to him: to modulate the quartz master oscillator with an identification signal. At the moment, this radio beacon transmits the line "CQ CQ CQ DE UA0LTB UA0LTB UA0LTB QTH LOC PN53XC" by tone telegraph, pauses for about 2 seconds, then everything repeats. This makes it easy to recognize the beacon signal on the air. The firmware is written entirely in C and occupies 1700 bytes in the microcontroller's memory.
And here is the diagram: 
Anticipating possible questions from skeptics like "Well, what the hell are you doing here!?", I answer:
1) Despite the apparent complexity of the circuit, the presence of chokes DR2, DR3, DR4 and DR6 is necessary here and pays off by the fact that the circuit becomes much more stable and stable in operation;
3) In parallel with each blocking electrolyte or ceramic, an additional blocking capacitor of small capacity (100-1000 pF) is also connected - to block the fundamental frequency and its higher harmonics. It also improves stability.
The application of all the above measures made it possible to obtain an absolutely stable and not prone to self-excitation design, even without additional screens between the cascades.
Achieved results in audibility. They are very good. During the competition "Nakhodka Cup on VHF - 2009" I received the signal of this beacon on a 144 MHz zigzag with a reflector, being 21 km south of Vladivostok, on Popov Island. And the beacon, respectively, was located in Vladivostok and worked with a power of 80 mW on an antenna of the "λ / 4 pin" type
There were also reports of good audibility of this beacon from UA0LGC in the village of Volno-Nadezhdinsky (30 km from Vladivostok) and from UA0LNL from the city of Artyom (about 35 km from Vladivostok).
And finally, some interesting observations:
1) Attempts to apply the same classic editing already at 430 MHz did not lead to anything good. The circuit turned out to be prone to self-excitation and no tricks led to an increase in the stability of its operation. In short, thanks to this beacon, I made an important conclusion for myself: classical editing is really applicable up to a frequency of about 150 MHz, at 430 MHz it is already of little use, it is better to use planar editing here, and only planar editing is applicable at frequencies of 900 MHz and higher;
2) Classical transmitters with quartz frequency multiplication, without the use of special measures, as a rule, have a disgusting output spectrum, where all harmonics of the quartz frequency are present at the output. But near the output frequency, the spectrum is very clean. Synthesizers are the opposite: near the output frequency the spectrum is dirty, there are a lot of side noises and so-called spurs, but they do not have a bouquet of subharmonics and far from the main frequency the spectrum is very clean;
3) Many novice radio hooligans, I think, came up with the idea - to buy a simple car FM transmitter with 1-2 transistors, add a 100-watt power amplifier to it and start "BROADCASTING". I hasten to disappoint you, dear novice radio hooligans: nothing good will come of this venture! The fact is that this transmitter will almost certainly have a very dirty unfiltered output spectrum and by connecting a power amplifier to it, you will get not a "broadcast station", but a real jammer of the entire FM range! And then you will cover all the TV within a radius of hundreds of meters! In general, those approaches that work well for low power transmitters, beacons, and radio bugs are completely unsuitable for powers of more than a few watts;
4) In order to communicate for tens of kilometers on VHF, it is often quite ridiculous by the standards of HF powers - about 10-100 mW. But at the same time, a couple of conditions are needed: good directional antennas and the absence of obstacles, and even better - direct visibility.
Vadim, UA0LTB
Vladivostok
06/04/2010
144 MHz radio beacon
More than 2 years have passed since the first version of the 144 MHz radio beacon was manufactured. After considering and weighing all the pros and cons, I decided to abandon the classic quartz circuit with frequency multiplication in favor of the synthesizer version.
I decided to replace the expensive synthesizer chip - LMX2346 (besides, available only on order), which I used earlier in beacons for the 430 and 1200 MHz bands, with something simpler and cheaper. At first I decided to do it on the LM72131, but I could not get a socket for it, since this microcircuit has a non-standard pitch between the pins - 1.78 mm. I had to give up in favor of its predecessor LM7001, which, although considered obsolete, is sold everywhere and is very inexpensive (at the time of this writing - 40 rubles in our Omega radio store. In addition, the LM7001 has fewer legs and a standard DIP-type case , and not the devil, like the LM72131.
I decided to replace the ATtiny2313 beacon controller with an ATtiny45, for the same reason - it is small, requires less strapping, and fewer legs. But, despite its smaller size, the ATtiny45 baby carries more memory on board, which made it possible to cram twice as many sine function samples into the program and, accordingly, generate a slightly better sine wave for tone modulation. It is not noticeable by ear, but according to the instruments, the level of the 2nd harmonic has decreased by about 2-3 dB.
In the radio frequency part of the beacon, I decided to pay tribute to the USSR-ovsky more transistors and used KP303B and KT368BM. They work great, by the way. Nostalgia-nostalgia! For a long time I have not done anything on Soviet parts, for the last 15 years everything has been only on bourgeois ones. And so I decided to "remember the past" :) I did not regret it.
Brief table of parameters for the 144 MHz beacon version 2
Working frequency - 144.700 MHz
Power-2mW-5W
Oscillator type - Synthesizer
Type of m / s synthesizer - LM7001
Output stage - SC-1265
Modulation - FM, tone telegraph
This radio beacon is assembled on an ordinary circuit board and, like all previous designs, is placed in a standard 110 * 60 * 30 mm silumin box. An antenna connector of the SO-259 type is attached to the side, since, as the experience of operating previous designs has shown, BNC connectors are unreliable, often popping out of their sockets. Connectors like PL-259 - SO-239 are also not ideal, but they hold on stronger, especially if they are tightened well :) Also on the side are: output power regulator, m / s synthesizer programming indicator (3 mm yellow LED) and terminals "+" and "-".
I decided to make the radiator passive, since active cooling often interferes with the power circuits and thereby pollutes the output signal of the beacon.
Here's what the finished design looks like: 
And here is the diagram: 
This is how the beacon board looked after the installation and commissioning work was completed. As practice has shown, such an installation works fine on HF and VHF up to 144 MHz inclusive, but is completely inapplicable on 430 and above. 
In the process of manufacturing and adjusting the beacon, this aluminum plate made my life much easier: 
Sawed to the size of the inner part of the future case, it made it possible to set up the beacon with relative ease, acting as a heat sink for the PA output line and the basis for mounting the circuit board. After finishing the setup, all I had to do was drill holes in the main body, using this plate as a template. And for future developments in the same case, this record will be very useful to me.
Here is a view of the finally assembled beacon without a cover: 
Vadim, UA0LTB
Vladivostok
06/11/2011
1200 MHz radio beacon
It has been about 3 years since the first version of the 1200 MHz radio beacon was manufactured. And finally, I managed to get a power amplifier for the 1.2 GHz range - the SC-1197 PA line, this is what it looks like 
Slightly digressing from the topic. This SC-1197 line seems to have Icom's designation (SC-xxxx), but for some reason there is a Mitsubishi badge on its body (the fan is such a diamond, although in fact it is a diamond), and outwardly this line is nothing from Mitsubishi is no different. But Mitsubishi has a different designation for such things - Mxxxxx. In general, it looks like we have a bourgeois cooperative here: they are made by Mitsubishi, but by order of Ikom and for Ikom. That's how things are.
Then I somehow didn’t really want to experiment and I began to think about making another beacon, a new one, with more power, and possibly on a different synthesizer chip. And the beacon of the first version - leave it as it is, because it worked well without a power amplifier :)
And one day, quite by accident, while wandering the Internet, on the wonderful site vhfdx.ru, I came across Edward's ad, RZ6APQ with the heading "I will give two identical frequency synthesizers on the MC12210 chip" and this photo: 
In addition to the MC12210 synthesizer microcircuit itself, the MC33172 operator in the varicap control circuit, the MMIC MSA0386 and the 5-volt planar roll were visible on the printed circuit board. Interested :)
Wrote Edward a letter, received a response. After 3 weeks, I had handkerchiefs, for which a huge amateur radio THANKS to Eduard!
The very first test of the synthesizers showed that the tuning range of the VCO "a is 900-1600 MHz when the voltage on the varicaps changes from 1 to 8 volts, just what you need!
He immediately sat down to manufacture, so to speak, an "exciter unit" - a synthesizer board with a controller and a reference oscillator in one bottle, that is, a case.
Having estimated all the dimensions, I soldered just such a box of tinplate from a can of condensed milk and foil fiberglass: 
Then I installed mounting racks from computer motherboards in the box and drilled holes in the partition for connecting wires and numbered them all so as not to get confused, because there are a lot of wires, and I'm alone :-):
For the reference oscillator at 12800 kHz and the ATtiny45 microcontroller, I sawed a piece of the circuit board to size, this is what I got at this stage: 
Soldered, turned on, works well, modulation is clean, without distortion. The output power is enough to drive the SC-1197 line up to 1.2 watts output, hooray! :) Everything works beautifully and steadily, there are no self-excitations.
I drove for several days in a frameless form, in the form of a ball of wires and cables - it works! Just think, the frequency is 1.2GHz and almost a hinged installation - and it works!
Before closing the lid, I thought a little about how to make a screen for the exciter unit? Well, just in case. Of course, they all work anyway, but experience suggested that you still need to shield :) I came up with the following idea: I glued a soft brass mesh to the bottom of the case and to the lid on a double-sided car tape. When tightening the structure with screws, the mesh is pressed into the adhesive tape (it is also soft) and fits snugly to the edges of the exciter block. In general, a minimum of costs with a good result:
Of course, copper foil would have been even better here, but I didn’t have it at that time. Therefore, I had to be content with a brass mesh.
And here is the final view of the finished structure: 
And the schema: 
Brief table of 1200 MHz beacon parameters
Operating frequency - 1294.400 MHz
Power-1.2W
Generator type - Synthesizer
Type m/s synthesizer-Motorola MC12210
Output stage-SC-1197
Modulation-FM, tone telegraph
In conclusion, I would like to give here one of my observations: when you make some kind of synthesizer, there is always a temptation to use either the clock generator of the microcontroller as a reference for the synthesizer microcircuit, or vice versa - use the synthesizer's reference to clock the microcontroller. So, never do that! That in one, that in another case, the result will be terrible. A sharp increase in the phase noise of the synthesizer plus contamination of the output signal of the synthesizer with artifacts of the microcontroller. That is why in this and my other designs the microcontroller is always clocked from the internal clock generator. And the synth support is also always separate, and with good power decoupling.
Vadim, UA0LTB
Vladivostok
24.07.2011
BEACON FOR TUNING VHF RECEIVERS AND ANTENNAS
Nikolai Myasnikov (UA3DJG), Ramenskoye, Moscow Region
With this "Beacon" you can adjust the receiving paths of transceivers in the ranges of 2 meters, 70 centimeters, 23 centimeters to maximum sensitivity, remove the antenna pattern of these ranges, compare them by gain, and so on. The presence of a 50 ohm output allows you to measure the gain of VHF preamplifiers and fine-tune their input circuits. "Beacons"-generators have been used by radio amateurs for a long time, and therefore this article can be considered only as a description of a specific design. The device is quite simple and can be considered as a "weekend design." The "beacon" circuit is shown in the figure 1.
It is a quartz oscillator assembled according to a capacitive three-point circuit. The frequency of the ZQ-1 quartz resonator must be such that its harmonics fall within the ranges of 144.432 and 1296 MHz. These can be resonators at frequencies near 8000 and 16000 kHz. a quartz resonator at a frequency of 16000 kHz (fundamental frequency, but the frequency of the 3rd harmonic is 48 MHz on the resonator case). .With XW1, weaker RF signals are removed, which are emitted on the elements C9, R4 due to interference inside the device. This output is used to finalize the receiving paths, compare receivers in sensitivity, and so on.
The level of harmonic signals on connectors XW1 and XW2 can be changed in a wide range by adjusting the supply voltage of the device in the range from 2 to 12V. In this case, the signal frequency changes somewhat, but this can be easily compensated by setting the receiver. 432.060 and 1296.180 MHz, taken from the XW2 connector, "reject" the S-meter needle up to S9 + 20 ... 40 dB, and from the XW1 connector - about S9 and are regulated by reducing the supply voltage until it disappears. A dipole antenna is connected to the XW2 connector on the required range, and the "beacon" is placed at a distance of several wavelengths from the antenna under study (at the same height).
The "beacon" is fed from a stabilized source with a smooth change in the output voltage (or from an unregulated source with an output voltage of 12V through a variable resistor with a resistance of 1 kOhm, included as a voltage divider). Since the current consumption of the device is very small (1 ... 3 mA), it is convenient to use it as a "beacon" for checking and tuning antennas and power it from a galvanic or rechargeable battery for quite a long time. The device is mounted on a double-sided fiberglass board measuring 70 by 40 mm (Fig.
The contact pads (shown as black squares) are cut out along the contour in the foil using a cutter. The width of the slots between the contact pads and the common wire (white field) is at least 1.5 mm. made of the same material, and soldered in it on both sides from the top, a cover is soldered, on which the operating frequencies of the "beacon" are indicated in different ranges. Elements C10, SA1, XW1, XW2 are installed on the side walls. For ease of switching, connectors XW1 and XW2 can be installed side by side - on the same wall. Elements C9, R4 (with a minimum length of pins) are soldered by surface mounting - on the back side of the XW1 connector. At the same time, to ensure good matching in the 1296 MHz range, it is better to use the R4 resistor SMD-type. L1-series choke DM. The L2 coil is wound with a wire with a diameter of 0.6 mm on a mandrel with a diameter of 2.5 mm and contains 3 turns. The winding pitch is 1.2 mm.
Capacitor C1 corrects the fundamental frequency of the oscillator so that one of its harmonics falls into the beginning of the 144 MHz range. In this case, the frequency meter is connected to the output XW2, and the output of the coil L2 is temporarily soldered from the case. If the frequency of the quartz resonator falls into the required area even without correction, a jumper can be installed instead of capacitor C1.
ARTICLE BY THE PUBLISHER WITH THE PERMISSION OF THE EDITORIAL OF THE MAGAZINE "RADIO"
Currently, radio amateurs are increasingly mastering the VHF bands of 1296 and 2400 MHz. The latter, for example, is used to receive signals from the repeater of the AO-40 amateur radio satellite. Setting up the equipment and antennas of the high-frequency VHF bands is greatly facilitated by low-power transmitters - radio beacons.
The scheme of the radio beacon is shown in fig. 1. It consists of a master oscillator with quartz frequency stabilization, assembled on a transistor VT1, a buffer amplifier on a transistor VT2 and two varactor frequency multipliers using the capacitances of the collector junctions of transistors VT3 and VT4. The required harmonics are extracted by the L3C12 (2400 MHz) and L4C13 (1300 MHz) resonant circuits. Antennas are connected to coaxial female connectors XS1, XS2. The generator and amplifier are powered by a GB1 battery through an integrated voltage regulator assembled on a DA1 chip.
The device works like this. The master oscillator is excited at the frequency of the quartz resonator, in this case 100 MHz, included in the base circuit of the transistor VT1. An L1C4 circuit is installed in the collector circuit of the transistor, and a positive feedback signal is fed to the emitter circuit through a capacitive divider C2C3.
The signal from part of the turns of the coil L1 is fed to a resonant amplifier made on the transistor VT2. Its gain can be smoothly changed by resistor R6. The amplified signal from the L2C6 circuit is fed to the varactor frequency multipliers. The 24th harmonic of the signal (2400 MHz) is generated on the nonlinear capacitance of the collector junction of the transistor VT3, is allocated by the L3C12 circuit and fed to the output connector XS1. Quite similarly, the 13th harmonic (1300 MHz) arises in the circuit of the nonlinear capacitance of the collector junction of the transistor VT4 and is highlighted by the L4C13 circuit. Half-wave resonators are used in these resonant circuits.
Most of the details of the beacon are placed on a printed circuit board made of double-sided foil fiberglass with a thickness of 1.5 ... 2 mm, a sketch of which is shown in fig. 2. A metal screen with a height of at least 20 mm is installed along the edge of the board, which is closed with a metal cover. The switch is installed on the screen, and the output connectors are directly on the board.
In the device, in addition to those indicated in the diagram, it is permissible to use the following parts: a power stabilizer chip - 78L05, transistors VT1 and VT2 - KT368B, VTZ and VT4 - KT3101A. Trimmer capacitors C4 and C6 are used of the type KT4 - 25, C12 and C13 - KT4 - 27 (without leads), constant capacitors - K10 - 17v (without leads) or K10 - 17a with leads of the minimum length. Trimmer resistor - type SPZ - 19, fixed resistors - MLT, P1 - 4, P1 - 12. Coils L1 and L2 are frameless, they are wound with wire PEV - 2 0.6 on a mandrel with a diameter of 5 mm and contain 6 turns with taps from 1 and 2.5 turns and 2.5 turns, respectively, counting from the output connected to the power wire.
Half-wave resonators L3 and L4 are made of a strip of copper (preferably silver-plated) foil 0.5 mm thick and 6 mm wide in the shape of the letter "P". The top part has a length of 25 mm (L3) and 45 mm (L4), the side parts are 5 mm. Connectors are connected to the top at a distance of 3 mm from the sides, and transistors VT3 and VT4 - at a distance of 5 mm, as shown in fig. 2. Trimmer capacitors are soldered vertically in the middle of the top.
The output connectors are of the SMA type or similar, necessarily high-frequency, coaxial. Switch SA1 can be any, small. The device is powered by a 9 V battery of the "Krona", "Korund", "Nika" type or similar, the current consumption is 10 ... 12 mA.
As an antenna, you can use quarter-wave pieces of hard wire or half-wave vibrators, the design of which is shown in Fig. 3. They are made from pieces of cable PK50-2-22 or similar. Vibrator 1 is made from a length of 55 (2400 MHz) or 105 mm (1300 MHz). At the ends of the segments, the cable is stripped by 1.5 ... 2 mm, the braid and the central conductor are interconnected by soldering.
In the middle of the vibrator, at a length of 4...5 mm, the outer insulation is removed and the braid 2 is carefully cut so that a gap between its parts is about 2 mm. Then the braid at the cut point is tinned and the second feeder cable section 3 with connector 4 at the end is soldered to it - the braid is to one side of the vibrator, and the central conductor is to the other. The recommended length (together with the connector) of the feeder sections is 90 (2400 MHz) and 165 mm (1300 MHz).
A photograph of the mounted radio beacon (with the top cover removed) is shown in fig. 4.
Establishing a beacon begins with setting up a master oscillator and a buffer amplifier. The tuning resistor R6 is set to the middle position, the trimmer capacitor C4 achieves stable generation, and with the trimmer capacitor C6 - the maximum signal at the output of the amplifier. Then, with tuned capacitors C12 and C13, half-wave resonators are tuned to the corresponding frequencies according to the maximum output signal at the frequency of the desired harmonic.
In conclusion, resistor R6 sets the maximum level of harmonics at the outputs, while additional tuning of the circuits is carried out using tuned capacitors C4 and C6. If the amplifier will work unstably, then between the collector of the transistor VT2 and the tap of the coil L2, you must install a resistor with a resistance of 50 ... 100 ohms.
Well, spies, listened to the end? Neighbors are no longer talking on the phone, are they afraid? But the neighbors are thoughtful, they can still communicate with each other ... All this garbage! It's time to make device number 2, which will break them off here too. As you probably guessed, it is designed to listen to a normal conversation. I hope the field of manufacturing the device of the 1st you are already rummaging around in electronics, so I will load less. Here is the schematic of the device:
R1 - 2.2 kOhm, |
If you're not blind and your brains haven't worn out yet, then you've probably noticed that a few new details have appeared. Let's start with them. The first part - a crossed out triangle - indicates the antenna in the diagram. In this case, this means that the collector of the transistor VT1 must be soldered to a piece of wire 37 cm long. The part marked GB1 is the battery. Here, the one that is put in computers and calculators rolls perfectly, i.e. lithium "tablet" at 3V. Well, the most important thing. A circle with a wand next to which stands + - is a microphone. You can get it in phones, radio tape recorders, voice recorders, or go to the extreme to buy it in a store. In order not to grab a hemorrhoid with its connection, carefully see the picture below. If the microphone you got does not match the picture, then you can immediately sausage it with a hammer :)
Well, we sort of figured out the main details. It remains only to say that the coil contains 6 turns on the rod from the gel pen, and the transistor must be installed with our KT3107B or KT3107BM, which is one-cheeky. By the way, the wire for the coil this time is 0.5 mm. Now you can safely solder the device. Once enabled, everything should work immediately. The setup method is the same as in the first part of the article. Only if the frequency is not in the range of 88-108 MHz, but somewhere at 74, then you need to set the Conder C2 to 30 pF. OK it's all over Now. As always, I advise you to read the Criminal Code of the Russian Federation again and I wish you not to get zvizdyuley from your neighbor.
| simple bug |
L1 - 5-6 turns on a 4 mm mandrel. L2 - 4-5 turns inside or over L1. Wire 0.5 mm. I recommend experimenting with the ratio of turns and the location of the coils.
Transistor KT368 or KT3102, microphone from an imported phone, tape recorder. Usually the circuit works immediately after switching on. In any case, I recommend measuring the voltage at the base of the transistor with a high-resistance voltmeter - it should be about 1.1-1.2 V. If it is different, then you need to select the resistance R1 until everything is as it should be.
Sometimes the problems that arise are due to the fact that microphones manufactured by different companies differ in impedance (approximately 1.1 kOhm). If a large output power is not required, you can increase R2 to 200 ohms. In this case, the current consumption will be about 7 mA, which is about 100-150 hours of battery life.
You can also use other microphones such as "Pine" or MKE333, as well as power the microtransmitter from 3-5 V, but in this case you will have to change the resistance R1 so that the bias voltage at the base of the transistor is about 1.1-1.2V.
| Reliable |
The main feature is ease of setup and reliability.
This is the most common scheme that can be found on the Internet. It is distinguished by ease of assembly and adjustment, small size, and also its not very high stability. But for beginners, I would recommend it.
All the parts I used were in SMD cases (Size 0805) For starters, I advise you to take in case 1206
Between the plus and minus of the power supply (in parallel with the batteries), I advise you to put a capacitor with a capacity of 0.01 microns. The coil has 5-6 vit. wire with a diameter of 0.5 mm on a mandrel with a diameter of 4-5 mm (take a core from a gel pen) Power supply from 4.5v to 9v. Antenna - a piece of wire, 40 cm long. Microphone from a Chinese tape recorder, or any Chinese in general
Details on the board from left to right:
R 10k R 100k R 10k R 10k C 10n C 15pf
S0.1mk S0.1mk QT368a9 S15pf
KT3130a9 R 3k S75pf R100
Setting.
Tune the receiver to approximately 96 MHz. Connect the power supply (USE A KRON BATTERY or similar!!! Not a Chinese power supply). Turn the receiver tuning knob. If you can't hear yourself well- 1) Look for more 2) squeeze/stretch the coil. If no changes are heard in the receiver when the transmitter is turned on, it is likely 1) erroneous installation or 2) the second transistor is faulty
If it is audible, but bad, then 1) select another one instead of a resistor (on the board in the upper left corner of 10k). 2) you need to replace the first transistor.
This is how the bug turned out. Pretty small. To reduce the size, you can use an even smaller microphone, for example Pine, but still you can’t reduce the battery (krone battery) much.
| Verified |
Economical, compact transmitter for 96-108 MHz. See fig.
In those recent times, when bugs were still not so cool to drive, on Mitka you could see and buy several types of these products - in tee sockets, handles and parallelepipeds made of compound. Most of them were made according to the scheme below. We personally assembled several such devices (from different brands of parts) and made sure that the circuit worked and had good parameters - high frequency stability, high sensitivity (a very quiet whisper is clearly audible at a distance of 2 m) and a sufficient transmission range (when powered by 9V, to the player's receiver "SONY", in line of sight - at least 100 m, and in a reinforced concrete house - stable around the apartment, they did not try further). All details are easily accessible. Place it where you want - to the best of your imagination. Resistors (All 0.125 W) R1 - 50...110 k R2 - 300 k R3 - 200 Capacitors (Any) C1 - 47 H C2 - 510 C3 - 30 r C4 - 8.2 r C5 - 120 r Transistor - VT1 - KT368. Its gain must be at least 150. The material of the case does not matter, but plastic seems to be better.
KT368 in plastic
KT368 in metal
Microphone "Pine"
If you want to place a bug in a flat thing (for example, in a calculator), then you can use the planar transistor KT3101. Then L1 will contain 15 turns of wire 0.25 ... 0.3 and have a diameter of 1.5 mm. For a frequency of 96 MHz, the L1 coil contains 5-6 turns of PEL-1 wire (any insulated copper) with a diameter of 0.68 mm (0.5 - 0.8 mm) on a mandrel with a diameter of 5 mm. They write that the work of the bug improves if you wind L1 around the transistor case. As a rule, due to differences in the parameters of parts and the use of close ratings, the signal can be anywhere in the VHF band. The antenna is a piece of wire about 30 cm. To reduce the length of the antenna, you can try to make it resonant by winding a certain number of turns on a dielectric mandrel, which is selected empirically. It depends on the parameters of the design and the transistor. For example, on a mandrel with a diameter of 2.5 mm, the length of the antenna wound with a wire with a diameter of 0.16 mm was obtained from 40 to 60 mm. The design uses a compact microphone "Pine" (in the figure). Its actual dimensions are 9x5x2 mm. The higher the sensitivity, the better. This miracle of technology can be purchased at the Mitinsky market or at the Quartz store (here are its phone numbers: 963-61-20, 964-08-38). The selection of the microphone for the optimal current is carried out by the resistor R1 within 15 k. Do not neglect this, the work of the bug often improves, and sometimes due to poor selection of the value of this resistor, there may be very low sensitivity. Resistor R2 should select the DC bias of the transistor. If oscillations are not excited, then C4 must be selected (if the circuit is assembled correctly). The antenna is tuned to resonance as follows: the antenna-wire is taken in advance of a greater length and, biting off 1 cm, using a field strength indicator (there are many circuits in the literature, nothing complicated) determine the maximum radiation. In this case, the current consumption should be minimal. The frequency is adjusted by compressing or expanding the turns of the coil L1. If you are sure of the correctness of your choice, then it is advisable to fill it with a compound (epoxy, worse "Moment") in order to avoid frequency drift from thermal expansion, mechanical influences and the microphone effect (tap the coil while the transmitter is operating and hear a rattle in the receiver). The receiver in the experiments can be any receiver with a VHF band (preferably extended - 65-109 MHz).
| FM micro transmitter |
The ratings of the parts are not critical and may differ in one direction or another by one and a half times. I received the signal of this bug, working in a reinforced concrete room at a distance of about 300 m, with no direct line of sight to the player's receiver. Bass sensitivity allows you to listen to a loud conversation in the room. If the low-frequency path is supplemented with another amplification stage, then even a quiet whisper becomes audible ... However, from loud speech, the circuit is then overloaded and you still need to set the AGC. If you need a transmitter - a radio microphone (when you plan to directly mumble directly into the microphone capsule), then the bass amplification stage is not needed at all.
Microphone - telephone electret capsule (also used in tape recorders). There are two pins on the back board, one of them is connected to the microphone body. This is a negative conclusion - a common one. Power is supplied to the second contact through a 5 ... 20 kΩ resistor. If the gain is too high, turn on a resistance of 100 Ohm ... 10 kOhm in the emitter circuit of the first transistor. The resistor in the emitter circuit of the second transistor determines the operating current of the RF generator. Do not reduce its value below 50 ohms - the transistor will be overloaded. Increasing the resistance improves generator stability and battery life, but reduces output power. The winding diameter of the contour coil is 5 mm, the wire is 0.5 mm. Number of coil turns for FM range 5-6. Roughly the operating frequency is set by the tuning capacitor of the circuit, and precisely by stretching / compressing the turns of the coil. It is desirable to replace the trimmer capacitor with a constant of the required capacity. The coupling coil is located next to the "hot" side of the loop coil coaxially at a distance of 2 mm and contains 4 turns of the same wire. The convergence of the coils (up to the winding of the coupling coil over the loop coil) and the increase in the number of turns of the coupling coil increases the useful power in the antenna, but reduces the frequency stability due to the effect of the antenna capacitance on the loop tuning (since there is no power amplification stage). Therefore, limit yourself to the maximum possible communication depth, at which the influence of the location of the antenna in space and touching it with your hands does not lead to a noticeable shift in the transmitter frequency.
The microtransmitter generator is made on a high-frequency transistor VT1 of direct conduction of the KT361 type, between the base and the emitter of which the circuit C1, L1 is connected. Coil L2 is used to communicate with the line, which in this case plays the role of an antenna.
The disadvantages of this device are a small range and the presence of a network background due to the lack of a voltage stabilizer. However, these shortcomings are offset by the exceptional simplicity and low cost of this device. Coil L1 contains 4...6 turns of PEV wire 0.5 mm in diameter 6 mm for the range 65...108 MHz.
The transmitter is included in the telephone line break.
1.5 V powered bug
Here I am writing this article and I think, well, is there really little literature written on the topic of bugs? This is me to the fact that there are people thinking letters with a request to send some kind of circuit for a bug powered by 1.5 V. In general, wash, of course, whoever needs or is interested, if I can, then I will help, or if you are interested in an idea, then I will come up with a scheme and tell everyone . Don't be offended if some emails go unanswered. In general, I came across a lot of schemes, but it seems that the Chinese have surpassed everyone in their ingenuity. And now in the crowd or where else you can buy a radio microphone that has good characteristics and is powered by just one AA battery. Its scheme is obscenely simple, however, like all Chinese electronics. Works somewhere in the FM range.
This miracle of the Chinese electronics industry "beats" almost 50 meters. And it works from a finger battery for a little more than a day (this is what kind of battery you will snatch). When setting up, it is necessary to select the bias voltages at the bases of transistors in the range of 0.6-0.7 V. L1, L2 are wound on a common frame, all coils are 4 mm in diameter. L1 - 5 turns, L2 - 3 turns with 0.2 mm wire. L3 - something like 4 turns of 0.6 mm wire. Transistors need to be slapped at a higher frequency: KT399, KT368, the unpackaged one is also suitable.
Radio microphone on the 1st transistor with a modulating circuit, range up to 150 meters. 
Stable radio microphone on a kt315 transistor, power supply - 9 volts, range - 50-120 meters, depending on obstacles. 
This is perhaps the most ultra-efficient radio transmitter in the history of their creation. It is powered by 1.5 volts, any sound source serves as a signal source, the range is ten meters. 
This transmitter is cxem.net's own development. It has been assembled and tested many times. All details are very carefully selected. The main advantage of this scheme is that there is no frequency drift and a decent range of action - up to 300 m. True, some experience is needed to establish this scheme. Details: VT1 - any transistor type KT315 (KT3102). Choose depending on the required microphone sensitivity. VT2, VT3 - KT368 (Gain factor - not less than 100). It is desirable to use in a metal case. M1 - microphone type "pine", MKE-3 or some imported. L1 - 3 turns with 0.5 mm wire on a 5 mm rim. L2 - 2 turns with 0.5 mm wire on a 5 mm rim. L3 - 8 turns with 0.25 mm wire on a 5 mm rim. After assembly, it is desirable to place the entire circuit in a metal case. The scheme was developed by: Look Andrey, typed and published by: Anatoly Koltykov. This diagram is protected by copyright. When copying this material, a link to http://cxem.net is required. 
Another 1.5 volt circuit:
Wire 0.3 mm, on the mandrel 2.5 mm.
L1 - 8 turns.
L2 - 6 turns.
L1 I personally wound 7, otherwise I had to stretch it a lot. This will be played during setup 
The working scheme of the bug, but when powered by a voltage of 3 volts, the range will double, also when using a long antenna in the form of a wire. 
Microtransmitter with current stabilization The scheme of the proposed miniature device differs markedly from the above. It is easy to set up and manufacture, allows you to change the frequency of the master oscillator over a wide range. The device remains operational when the supply voltage is above 1 V. The radio transmitter circuit is shown in fig.
The high frequency generator is assembled according to the multivibrator circuit with an inductive load. The change in the frequency of high-frequency oscillations occurs when the current flowing through transistors VT1, VT2 of the KT368 type changes. When the current changes, the conductivity parameters of the transistors and their diffusion capacitances change, which makes it possible to vary the frequency of such a generator over a wide range without changing the frequency-setting elements - coils L1 and L2. To increase the frequency stability and to be able to control the generator in order to obtain frequency modulation, the latter is powered through a current stabilizer. The stabilizer and the modulating amplifier are made on an electret microphone M1 type MKE-3, M1-B2 "Pine" and the like. When using standard parts, the carrier frequency drift when the supply voltage changes from 1.5 to 12 V does not exceed 150 kHz (with an average generator frequency of 100 MHz). The circuit uses frameless coils L1 and L2 with a diameter of 2.5 mm. For the range of 65-108 MHz, the coils contain 15 turns of PEV 0.3 wire. The tuning consists in adjusting the frequency by changing the inductance of the coils L1 and L2 (compressing or stretching). The generator in question can operate at frequencies up to 2 GHz, when using transistors such as KT386, KT3101, KT3124 and the like, and when changing the design of the loop coils.
Miniature battery-powered radio transmitter for electronic clocks
The device contains a minimum of necessary parts and is powered by a 1.5 V electronic clock battery. With such a low supply voltage and a current consumption of 2-3 mA, the signal of this radio microphone can be received at a distance of up to 150 m. The operating time is about 24 hours. The master oscillator is assembled on the transistor VT1 type KT368, the mode of operation of which is set by the direct current resistor R1. The oscillation frequency is set by the circuit in the base circuit of the transistor VT1. This circuit includes a coil L1, a capacitor C3 and a capacitance of the base-emitter circuit of the transistor VT1, in the collector circuit of which a circuit consisting of a coil L2 and capacitors C6, C7 is included as a load. Capacitor C5 is included in the feedback circuit and allows you to adjust the level of excitation of the generator.
In self-oscillators of this type, frequency modulation is performed by changing the potentials of the outputs of the generating element. In our case, the control voltage is applied to the base of the transistor VT1, thereby changing the bias voltage at the base-emitter junction and, as a result, changing the capacitance of the base-emitter junction. A change in this capacitance leads to a change in the resonant frequency of the oscillatory circuit, which leads to the appearance of frequency modulation. When using an imported VHF receiver, the required maximum carrier frequency deviation is 75 kHz (for the domestic standard - 50 kHz) and is obtained by changing the audio frequency voltage based on the transistor in the range of 10-100 mV. That is why this design does not use a modulating audio frequency amplifier. When using an electret microphone with an amplifier, for example, MKE-3, MKE-333, MKE-389, M1-B2 "Sosna", the signal level taken directly from the microphone output was sufficient to obtain the required frequency deviation of the radio microphone. Capacitor C1 filters high frequency oscillations. Capacitor C7 can change the value of the carrier frequency within a small range. The signal enters the antenna through capacitor C8, the capacitance of which is specially chosen to be small in order to reduce the influence of disturbing factors on the oscillation frequency of the generator. The antenna is made of a wire or a metal bar 60-100 cm long. The length of the antenna can be reduced if an extension coil L3 is included between it and the capacitor C8 (not shown in the figure). The coils of the radio microphone are frameless, with a diameter of 2.5 mm, wound round to round. Coil L1 has 8 turns, coil L2 - 6 turns, coil L3 - 15 turns of PEV 0.3 wire. When setting up the device, they achieve the maximum high-frequency signal by changing the inductances of the coils L1 and L2. By selecting capacitor C7, you can slightly change the value of the carrier frequency, in some cases it can be completely eliminated. Andrianov V.I., Borodin V.A., Sokolov A.V. "Spy stuff and devices for protecting objects and information", p.47
I propose a simple radio microphone circuit (Fig. 1). The circuit is assembled on a single transistor of the KTZ15V type (when installing transistors with letter indices G, E, Zh and I, the resistance of the resistor R2 should be increased). The low frequency generator is a microphone. It can be either carbon or electret.
When using different microphones, the resistance of the resistor R1 should be selected. For example, for an electret microphone, it is in the range of 4.7 ... 5.6 kOhm. The radio microphone is powered from a power source with a nominal voltage of 9 V. It can be a Krona battery or a 7D0.1 rechargeable battery. When using other batteries with a lower voltage, reduce the resistance of resistors R1 and R3. If an electret microphone is used in the design, the voltage on it must be at least 1.5 V, and the radio microphone current must be at least 90 mA. Correctly assembled, without errors and on serviceable parts, the circuit immediately starts working. Setting up the radio microphone consists in expanding and compressing the turns of the L1 coil. It contains 7 turns of copper wire with a diameter of 0.2 ... 0.45 mm, wound on a mandrel with a diameter of 3 ... 5 mm. As an antenna, you can use 10 ... 30 cm of copper wire. with a diameter of 0.45 ... 1 mm. The range depends on the length (dimensions) of the antenna. For example, with an antenna length of 20 cm, the range of the radio microphone is 15 m. D. AVDEEV, 230009, Grodno-9, BLK, 34/1 - 4.
FM radio microphone 65...108 MHz This transmitter, with modest dimensions, allows you to transmit information at a distance of up to 300 meters. Signal reception can be carried out on any VHF FM band receiver. Any source with a voltage of 5 ... 15 volts is suitable for power supply. The transmitter circuit is shown in fig.
The master oscillator is made on the KP303 transistor. The generation frequency is determined by the elements L1, C5, C3, VD2. Frequency modulation is carried out by applying a modulating audio frequency voltage to the VD2 varicap type KV109. The operating point of the varicap is set by the voltage supplied through the resistor R2 from the voltage regulator. The stabilizer includes a stable current generator based on a field-effect transistor VT1 type KP103, a zener diode VD1 type KS147A and capacitor C2. The power amplifier is made on a transistor VT3 type KT368. Its mode of operation is set by resistor R4. A piece of wire 15 ... 20 cm long is used as an antenna. Chokes Dr1 Dr2 can be any inductance 10 ... 150 μH. Coils L1 and L2 are wound on polystyrene frames with a diameter of 5 mm with interlaced cores 100VCh or 50VCh. The number of turns is 3.5 with a tap from the middle, the winding pitch is 1 mm, the PEV wire is 0.5 mm. Instead of KP303, KP302 or KP307 will do. The setting consists in setting the required frequency of the generator with the capacitor C5, obtaining the maximum output power by selecting the resistance of the resistor R4 and adjusting the resonant frequency of the circuit with the capacitor C10.
Radio transmitter with AM in the frequency range 27-28 MHz
The device described below is a 27-28 MHz AM transmitter. The range is up to 100 m. The transmitter consists of a high-frequency generator assembled on a VT2 transistor of the KT315 type, and a single-stage audio frequency amplifier based on a VT1 transistor of the KT315 type. At the input of the latter, through the capacitor C1, an audio signal is received from the microphone M1 of the "Pine" type. The amplifier load is made up of resistor R3 and a high-frequency generator connected between the plus of the power source and the collector of transistor VT1. With signal amplification, the voltage at the collector of transistor VT1 changes. This signal modulates the amplitude of the signal of the carrier frequency of the transmitter generator, emitted by the antenna.
The design used MLT-0.125 resistors, capacitors - K10-7V. Instead of KT315 transistors, you can use KT3102. Coil L1 is wound on a polystyrene frame with a diameter of 7 mm. It has a tuned 600HN ferrite core with a diameter of 2.8 mm and a length of 12 mm. Coil L1 contains 8 turns of PEV wire 0.15 mm. Winding - turn to turn. Inductor Dr1 is wound on an MTL-0.5 resistor with a resistance of more than 100 kOhm. The inductor winding contains 80 turns of PEV 0.1. A steel elastic wire 20 cm long is used as an antenna. When tuning, the frequency is set by adjusting the inductance of the coil L1. After adjustment, the tuning core of the coil is fixed with paraffin.
Andrianov V.I., Borodin V.A., Sokolov A.V. "Spy stuff and devices for protecting objects and information", 1996, p.51
Medium power radio transmitter with compact loop antenna
The device operates in the range of 65-73 MHz with frequency modulation. The range when using a frame compact antenna is about 150 m. The duration of the device when using batteries "Krona" is 30 hours.
The low-frequency signal of the M1 microphone of the type MKE-3, "Pine", etc. is amplified by a two-stage low-frequency amplifier with direct connections. The amplifier is made on transistors VT1 and VT2 type KT315. The operating mode of the amplifier is set by resistor R2. The master oscillator of the device is made on a transistor VT3 type KT315. The frequency-setting circuit is connected to the base of the transistor VT3 through a small capacitor C6. Capacitors C8, C9 form a feedback circuit. The generator circuit consists of an inductance L1, a capacitor C5 and two counter-connected diodes of the KD102 type. Under the action of the modulating voltage, the capacitances of the diodes VD1, VD2 change. Thus, the frequency modulation of the transmitter is carried out. From the output of the generator, the modulated signal is fed to the power amplifier. The output amplifier is made on a transistor VT4 type KT315. It works with high efficiency in class "C" mode. The amplified signal enters the loop antenna, made in the form of a spiral. The spiral can be of any shape, it is only important that the total length of the wire is 85-100 cm, the diameter of the wire is 1 mm. Inductors Dr1, Dr2 - any, with an inductance of about 30 μH. Coils L1, L2, L3, L4, L5 - frameless, 10 mm in diameter. Coil L1 has 7 turns, L2 and L4 - 4 turns each, L3 and L5 - 9 turns each. All coils are wound with 0.8 mm PEV wire. Setting up the transmitter has no special features.
Andrianov V.I., Borodin V.A., Sokolov A.V. "Spy stuff and devices for protecting objects and information", 1996, p.54
Radio transmitter with FM in the VHF frequency range 61-73 MHz
The radio transmitter is a single-stage VHF FM transmitter operating in the broadcast band 61-73 MHz. The output power of the transmitter when using a 9-12 V power supply is approximately 20 mW. It provides an information transmission range of about 150 m when using a receiver with a sensitivity of 10 μV. The modes of the UZCH transistors (VT1) and the RF generator (VT2) for direct current are set by resistors R3 and R4, respectively. A voltage of 1.2 V is supplied to them and to the power supply of the microphone M1 from a parametric stabilizer to R1, C1, VD1. Therefore, the device remains operational when the supply voltage drops to 4-5 V. In this case, a decrease in the output power of the device is observed, and the carrier frequency changes slightly.
The modulating amplifier is made on a transistor VT1 type KT315. The audio frequency voltage at its input comes from an electret microphone with an M1 amplifier of the MKE-3 type and the like. The amplified audio frequency voltage from the collector of the transistor VT1 is supplied to the KV109A type VD2 varicap through a low-pass filter to resistor R5 and capacitor C5, and resistor R7. The VD1 varicap is connected in series with the trimmer capacitor C8 in the emitter circuit of the transistor VT2. The oscillation frequency of the master oscillator, made on a transistor VT2 type KT315 (KT3102, KT368), is determined by the circuit elements L1, C6, C7 and the capacitance C8 and VD1. Instead of the VD1 LED of the AL307 type, you can use any other LED or three diodes of the KD522 type and the like connected in series in the forward direction. The L1 coil is frameless, 8 mm in diameter, has 6 turns of PEV 0.8 wire. When setting up, the transmitter is tuned to a free section of the VHF FM range by compressing or stretching the turns of the coil L1 or adjusting the capacitor C8. The frequency deviation is set by the capacitor C8 according to the highest quality reception on the control receiver. The transmitter can also be tuned to the VHF FM broadcast range (88-108 MHz), for this it is necessary to reduce the number of turns L1 to 5 and the capacitance of capacitors C6 and C7 to 10 pF. A piece of wire 60 cm long is used as an antenna. To reduce the influence of destabilizing factors, the antenna can be connected through a capacitor with a capacity of 1-2 pF.
Andrianov V.I., Borodin V.A., Sokolov A.V. "Spy stuff and devices for protecting objects and information", 1996, p.50
Broadband FM radio transmitter in the frequency range 65-108 MHz
The radio microphone operates in the frequency range of 65-108 MHz with broadband frequency modulation. This allows you to receive a signal from a radio microphone to a conventional FM receiver in this range. The range of action reaches 150-200 m. The duration of work with a KRONA-type battery is about 10 hours.
Low-frequency oscillations from the output of the microphone M1 (type MKE-3, M1-B2 "Pine" and the like) through the capacitor C1 are fed to the audio frequency amplifier, made on the transistor VT1 type KT315. The amplified audio frequency signal, taken from the collector of the transistor VT1, through the inductor Dr1 acts on the varicap VD1 (type KV109A), which performs frequency modulation of the radio signal generated by the high-frequency generator. The RF generator is assembled on a VT2 transistor of the KT315 type. The frequency of this generator depends on the parameters of the circuit L1, C3, C4, C5, C6, VD1. The RF signal taken from the collector of the VT2 transistor is amplified by a power amplifier based on the VT3 transistor of the KT361 type. The power amplifier has a galvanic connection with the master oscillator. Amplified high-frequency voltage is released at the inductor Dr2 and enters the U-shaped circuit, made on the elements C11 L2, C10. The latter is configured to pass the main signal and suppress many harmonics that occur on the collector of the transistor VT3. The radio microphone is assembled on a board measuring 30x70 mm. A piece of mounting wire 25 cm long is used as an antenna. All parts are small-sized. Resistors - type MLT-0.125, capacitors - K50-35, KM, KD. Instead of a VD1 varicap of the KV109A type, varicaps with a different letter index or a KB102 varicap can be used. Transistors can have any letter index. Transistors VT1 and VT2 can be replaced with KT3102, KT368, and transistor VT3 - with KT326, KT3107, KT363. Inductors Dr1 and Dr2 are wound on MLT 0.25 resistors with a resistance of more than 100 kOhm with a PEV 0.1 wire of 60 turns each. Coils L1 and L2 are frameless, 5 mm in diameter. Coil L1 - 3 turns, coil L2 - 13 turns of PEV wire 0.3. The tuning comes down to setting the frequency of the master oscillator, corresponding to the free section of the VHF FM band, by changing the capacitance of the tuning capacitor. By stretching or compressing the turns of the L2 coil, the transmitter is tuned to the maximum power of the RF signal.
Andrianov V.I., Borodin V.A., Sokolov A.V. "Spy stuff and devices for protecting objects and information", 1996, p.53
VHF FM radio transmitter with a range of 300 m
This transmitter, with a very small size, allows you to transmit information at a distance of up to 300 m. Signal reception can be carried out on any VHF FM receiver. Any power source with a voltage of 5-15 V can be used for power supply. The transmitter circuit is shown in Fig. 1
Rice. 1. The master oscillator of the transmitter is made on a field-effect transistor VT2 of the KPZOZ type. The generation frequency is determined by the elements L1, C5, C3, VD2. Frequency modulation is carried out by applying a modulating audio frequency voltage to the VD2 varicap type KB 109. The operating point of the varicap is set by the voltage supplied through the resistor R2 from the voltage stabilizer. The stabilizer includes a stable current generator based on a field-effect transistor VT1 type KP103, a zener diode VD1 type KS147A and capacitor C2. The power amplifier is made on a transistor VT3 type KT368. The operating mode of the amplifier is set by resistor R4. A piece of wire 15-50 cm long is used as an antenna. Inductors Dr1 and Dr2 can be any, with an inductance of 10-150 mH. Coils L1 and L2 are wound on polystyrene frames with a diameter of 5 mm with tuned cores 100VCh or 50VCh. The number of Tweets is 3.5 with a tap from the middle, the winding pitch is 1 mm, the PEV wire is 0.5 mm. Instead of the KPZ0Z transistor, you can use KP302, KP307. . The setting consists in setting the required frequency of the generator with the capacitor C5, obtaining the maximum output power by selecting the resistance of the resistor R4 and adjusting the resonant frequency of the circuit with the capacitor C10.
Simplified diagram of a radio microphone 88 - 108 MHz.
The radio microphone circuit for use in the VHF broadcast range of 88 - 108 MHz, published in "RA" N 8 - 10, 1993, p. 21, according to readers, showed good results. However, such radio equipment is subject to the requirement of minimum dimensions of the board and the entire product. For a better layout in the case, the width of the board is designed to match the length of the Corundum type element, but the principle of the electrical solution of the circuit itself is of paramount importance in minimizing the product. The author went along this path, expressing the wishes of radio amateurs. The first version of the circuit (see "RA" N 8 -10,1993) has increased sensitivity, which is not always useful in the operation of a radio microphone, since the signal is overmodulated at close and loud enough sounds. To eliminate this phenomenon, a limiting resistor R13 is introduced. However, it is more advisable to completely exclude the audio frequency amplification stage, which will allow, while maintaining quality indicators, to remove resistors R2.R13 and transistor VT1 from the circuit.
The previously published circuit has good output signal characteristics (frequency stability, quality factor of the circuit), which is achieved by building a high-quality oscillator based on two transistors VT4 and VT5. And in this case, in order to simplify the circuit, the RF generator can be performed on a single transistor. Indeed, for household radio microphones, due to the lack of master oscillators, quartz resonators, and amplification stages in the circuits, many radio engineering parameters are not critical. Therefore, the following elements are excluded from the circuit: resistor R11, capacitor C8 and transistor VT5, as well as inductor D1, since in a simplified version (see figure) due to the spread in the diameter of the wire, as well as errors in the diameter of its winding, the inductance of the inductor affects the operation of the circuit, which presents known difficulties for the radio amateur when setting up. A drawing of a simplified circuit board is not provided so that radio amateurs independently develop it, taking into account their capabilities (without wiring for a switch, with or without LED indication, etc.). All resistors of the MLT-0.125 type, electrolytic capacitors C1 - C4, C6 and C8 of the K50-16 type, high-frequency capacitors C5 and C8 of the KT-1 type. The length of the antenna can be reduced to 500 mm. The simplified scheme of the radio microphone, while maintaining the set technical requirements, is more economical than its prototype.
A.T.Zarudny, Kyiv, RADIOAMTOR No. 9, 1994
With frequency modulation on a varicap
A piece of 75 ohm antenna cable with a diameter of 3 and a length of 185 mm is used as an antenna. The central core is soldered directly to the capacitor C 9, the braid serves as a fastener. The microphone signal is amplified by a two-stage 3H amplifier on transistors VT1, VT2. The master oscillator is made on the transistor VT3. The frequency modulation of the carrier is provided by the VD1 varicap. Resistors R5, R6 in the base circuit of the generator transistor determine its DC mode. Capacitor C7 sets the required generation mode providing positive feedback. The capacitance of this capacitor must be selected according to the maximum current consumed by the generator, and then set this current to about 25 mA with resistor R5, since the VT3 transistor cannot work at a higher current.
When setting up, it is advisable to include a tuning capacitor with a capacity of 8 ... 30 pF in place of C7, and a tuning resistor with a resistance of 100 kOhm in place of resistor R5. The frequency stability of the generator depends mainly on the supply voltage. To increase it, you can use a voltage stabilizer for 6 ... 9 V. You can also stabilize the frequency of the generator in another way. To be precise, the reason for the instability of the carrier frequency is in the fluctuations in the operating point of the transistor of the output stage of the 3H amplifier when the supply voltage changes. The position of this operating point determines the reverse bias voltage on the VD1 varicap, and hence its initial capacitance, which will eventually change not only under the influence of an audio signal, but also when the supply voltage changes. The varicap is connected in series with the quartz and together with it determines the frequency of the generator. Therefore, it is possible to supplement the transmitter circuit with a device that provides a constant varicap bias voltage (Fig. 2), the value of which can be adjusted by resistor R1. Circuit R2, VD1 is a common parametric stabilizer. Capacitor C1 provides DC decoupling of the stages. When mounting the transmitter, fixed resistors MLT - 0.125, oxide capacitors K50 - 35 were used; small-sized ceramic capacitors of constant capacity, for example KM. Inductors L1, L2 can be used standard, for example, D - 0.1, with an inductance of 15 ... 30 μH, or made independently. To do this, on resistors MLT - 0.5 with a resistance of more than 100 kOhm, it is necessary to wind 30 ... 50 turns of PEL 0.1 wire along the entire length. The loop coil L3 is wound on a frame with a diameter of 8 mm and contains 6 turns of PEL 0.8 wire. Coils L4 are also wound on the same frame and with the same wire. Its winding contains 3 turns and is placed at a distance of 1 mm from the winding of the coil L3. A few words about the antenna. For its manufacture, a segment of a 50-ohm cable 10 ... 12 cm long is used, it is cleaned of insulation and braid and the central core is pulled out of it. Then, the socket of the C P - 50 - 74V connector is placed on the transmitter, to which the L4 coil (antenna connector) is connected. A piece of cable processed in the described way is fixed in the connector plug. Now it remains to wind along the entire length of the cable, turn to turn, PEL wire 0.6 - the antenna is ready. You just need to insert the plug into the antenna socket of the transmitter. In extreme cases, a metal pin 30 ... 50 cm long can be used as an antenna. When operating the transmitter, it was noticed that if you touch the common wire with your hand during transmission, the transmitter radiation power increases. In other words, the operator's body plays the role of an antenna counterweight here. If the transmitter is assembled in a plastic case, such a counterweight can be provided by connecting a piece of wire 1 m long to the common wire. If the case is metal, then it must be connected to the common wire. In this case, the counterweight is not needed, since its functions will be performed by the operator in whose hands the transmitter is located. As a microphone, you can use any small-sized microphone, except for carbon. Naturally, the sensitivity of the receiver will affect the communication range.
Sent by: Andrey Smirnov.
High efficiency bug
The bug is assembled according to the Hartley scheme with non-standard feedback, due to which it has an efficiency of 10-20% higher than similar schemes. This scheme is similar to that used in the simplest telephone bug. She has been surfing the Internet for a long time, and site owners continue to steal it from each other, not noticing a gross mistake in the scheme. This error has been corrected here.
R1=R3=R4 - 9.1 k,
R2 - 300 k,
C1 - 0.1 microfarad,
C2 - 56, C3 - 24,
VT1 - KT315,
VT2 - KT325VM,
L1 - 5+5 turns
PEV-0.5 wires on a 3mm mandrel.
As a rule, the circuit starts working immediately after assembly. If a squeak is heard in the receiver, the circuit should be shunted with a capacitor with a capacity of at least 1 microfarad. It is better to connect the antenna through a conder with a capacity of 1-2 pF. I had a range of 140m with an antenna length of 20cm.
VHF FM radio microphone for 60 - 100 MHz
Range - up to 400m. L1 - 5 ... 6 turns of PEL-0.5 with a tap from 2 turns on top. Microphone MKE-3, MKE-33 and others similar. Power 15-200 mW - depends on the current consumption 5-30 mA (set by selecting Rz 5-47 kOhm) Antenna 15-100 cm (flexible or rigid wire) or 75-100 turns PEL-1.0 per dia. 4 mm.
PHONE BUGS:
Scheme of a bug that does not need a transmitting antenna:
It does not need an antenna, since the antenna is a telephone pair. To increase the range, I advise you to put P416B instead of KT3102, but in this case you need to change the polarity of the bug's power supply. Coil L1 - frameless, with an inner diameter of 6 mm, contains 5 turns (for VHF), for FM - 4 turns of PEV wire - 0.7 ... 0.9 mm. The setting is made by changing the capacitance of the tuning capacitor, as well as compressing or stretching the turns of the L1 coil to receive a signal in the VHF (FM) range of the broadcast receiver free from broadcasting stations. The range with P416 is 250-300m in line of sight, and with KT3102 200-250m.
Beetle at 350m
Characteristics of the transmitter: range 180m with 4v power and 350m with UHF power: 1.5 ... 12v the transmitter transmits a signal with frequency modulation with good microphone sensitivity antenna a piece of wire 60cm long
Details:
transistor T1 can be excluded and on C4 apply a low-frequency varicap signal - any transistors-T1 KT3102E, T2-KT368 or S9018 inductor L1 for 100 μg coil L1 4wit with a 0.5mm wire on a 5mm frame addition to the transmitter power amplifier !!! power amplifier with a P-loop L1-5vit with the same wire L2-5vit with the same wire transistor-KT610 Power-0.6W if more power is not required, instead of KT610 on KT368, shunt the L2 coil in the master oscillator with a capacity of 15pF
Description: the signal from the microphone is selected on the resistor R4 and is fed through the capacitor C2 to the base of a single-stage amplifier on the transistor T1, the bias of the transistor sets the resistor R3; resistors R5 R6 are needed to bias the varicap varicap thereby performs FM because it changes the capacitance at the signal and this affects the frequency of the master oscillator. The master oscillator is the usual three-point capacitor C3, it is optional, it was soldered on the microphone itself, the resistor R2 and the capacitor C11 and L1 (this is a choke) form a filter so that the HF does not penetrate the ULF and does not disrupt its operation. and with a good antenna it reached 3 km capacitors C3 C4 C5 C10 will filter the constant component from the variable C3 C4 (In the power amplifier!) Select for setting the P-loop
