Do-it-yourself low-voltage fm VHF transmitter. Small-sized VHF FM transmitter circuits. Fig.1 Structure of the AL2602 chip
The Shmel VHF transmitter operates in the non-traditional range of 175-190 MHz with wideband frequency modulation. In order to increase the frequency stability of the master oscillator, the base circuit of the power amplifier transistor is powered from a voltage stabilizer (R5, LED1). SMD RED LED used. The frequency drift when the power supply drops from 3 to 2.2 volts is no more than 100 KHz. When you touch the antenna with your hand, the frequency also deviates slightly. If you have a receiver with a good AFC, it tracks this change and the frequency shift does not occur at all during the operation of the transmitter.Schematic diagram:
An additional microphone amplifier is not required, since whispers are perceived by the transmitter at a distance of 5-6 meters. Any suitable Chinese can serve as a receiver, for example “TECSUN R1012”.
This receiver already has a range of 175-223 MHz and the transmitter signal was “fairly” received at a distance of 400m (the device was on the 5th floor, reception in a city).
VHF transmitter details:
Microphone with a diameter of 6mm from one large eastern country.
- transistors, resistors, capacitors, LED-SMD.
- coils contain: L1-4 turns of copper wire in varnish insulation with a diameter of 0.4-0.5 mm, wound on a mandrel with a diameter of 2.5 mm.
- L2-20 turns of wire with a diameter of 0.31 mm, wound on a mandrel with a diameter of 2.5 mm
- the antenna is a piece of wire 62 cm long (don’t be surprised, but it has the best coordination and range).
- the author’s version uses a CR2450 lithium battery with a capacity of 560 mAh, the charge of which is enough for 80 hours of continuous operation of the bug. The device consumes about 7 mA of current.
Continuing the experiments, I decided to slightly remake the antenna without losing range, and this is what we have: winding length 50 mm, width of the antenna frame (textolite 0.5 mm) 8 mm, winding wire 0.25 mm. - until filled.
If it is not possible to find a receiver with extended frequencies, then Bumblebee works great on the FM band. And if you climb higher, then you need to do it not at 175-190, but at all 250 megahertz - it shoots further. Then I assembled the second “SHBELE” with a 62 cm antenna. The wire is a piece of MGTF 0.75.
Result: a reliable reception range through one reinforced concrete wall is 200m, and houses interfere with further movement, I did not notice a frequency shift at all, the sensitivity of the microphone completely controls the entire apartment, the sound is soft, clear, not annoying, as if AGC was working.
Finished the "beetle" with SMD inductors. The result exceeded expectations, namely, the reception range increased significantly, about 300m, although the current also increased slightly to 8 mA.
A new one was produced, the dimensions of the “Bumblebee” itself are determined mainly by the dimensions of the battery. Collect it, you won’t regret it - 100% repeatability, and there are no difficulties. I repeat once again: this is probably the most successful “insect” of the 2 transistor circuits. As they say - RESPECT AND RESPECT for the author! Assembly and testing: GOVERNOR.
Discuss the article VHF TRANSMITTER
We will talk about how to make the simplest and cheapest radio transmitter that anyone who doesn’t even understand anything about electronics can assemble.
Reception of such a radio transmitter occurs on a regular radio receiver (on a landline or in a mobile phone), at a frequency of 90-100 MHz. In our case, it will work as a radio extender for headphones from a TV. The radio transmitter is connected via an audio plug to the TV via a headphone jack.
It can be used for different purposes, for example:
1) wireless headphone extender
2) Radio nanny
3) A bug for eavesdropping and so on.
To make it we will need:
1) Soldering iron
2) Wires
3) Audio plug 3.5 mm
4) Batteries
5) Copper varnished wire
6) Glue (Moment or epoxy) but it may not be needed
7) Old boards from a radio or TV (if any)
8) A piece of simple textolite or thick cardboard
Here is his circuit, it is powered by 3-9 volts
The list of radio parts for the circuit is in the photo; they are very common and finding them will not be difficult. Part AMS1117 is not needed (just ignore it)
The coil should be wound according to the following parameters (7-8 turns with a wire with a diameter of 0.6-1 mm, on a mandrel 5mm, I wound it on a drill 5mm)
The ends of the coil must be cleaned of varnish.
A battery housing was used as a housing for the transmitter.
Everything inside was cleaned. For ease of installation
Next, we take the textolite, cut it and drill a lot of holes (it’s better to drill more holes, it will be easier to assemble)
Now we solder all the components according to the diagram
Take the audio plug
And solder the wires to it, which are shown in the diagram as (input)
Next, place the board in the case (it is most reliable to glue it) and connect the battery
Now we connect our transmitter to the TV. On the FM receiver we find a free frequency (one on which there is no radio station) and tune our transmitter to this wave. This is done by a tuned capacitor. We slowly turn it until we hear sound from the TV on the FM receiver.
Our transmitter is now ready for use. To make it convenient to set up the transmitter, I made a hole in the body
I am posting a small collection of schematic diagrams of radio transmitters collected from various foreign sites. Starting from low-power, a few milliwatts, and up to powerful multi-watt UHF amplifiers. I haven’t tested the functionality, but the circuitry inspires confidence. All transmitter circuits are designed for the standard broadcast VHF range 88-108 MHz.
FM Transmitter in a pen
The FM bug in a writing pen project is very popular among beginning radio amateurs. In an effort to reduce the size of this design, surface mount components are used. The circuit has low power consumption, but sufficient output power to cover a radius of 50 - 200 m. You can put watch batteries or a lithium-ion battery from the Bluetooth system here.
FM transmitter for 5 kilometers
The proposed broadcast transmitter is indeed very stable, has a complex, but high-quality and well-thought-out circuit design, and uses standard FM frequencies 88 - 108 MHz. Its range of action is a real 5 km. The circuit includes a stable generator powered through an LM7809 stabilizer - this is a 9 V stabilized power source, on transistor T1 and a frequency adjustment element 10K potentiometer. The RF output power of this transmitter is about 1 W. A pair of MV2019 varicaps function as variable capacitors.
The final stage of the FM transmitter is a powerful microwave transistor of at least one watt of power. You need to use transistors 2N3866, 2N3553, KT920A, 2N3375, 2SC1970 or 2SC1971. Do not forget to install an effective heatsink for the T5 transistor, because it becomes slightly warm during operation. The circuit will require a 12V/1A power supply.
Coil winding data:
- L1 = 5 turns on 4 mm frame
- L2 = 6 turns on 6 mm frame
- L3 = 3 turns on 7 mm frame
- L4 = 6 turns on 6 mm frame
- L5 = 4 turns on 7 mm frame
Everything is wound with a wire about a millimeter in diameter. Transistors T1 = T2 = T3 = T4 = BF199, T5 = 2N3866 or 2SC1971, BLY81, 2N3553.
15 W UHF for 88-108MHz range
The RF power amplifier amplifies all frequencies 88-108MHz from 1W input power received from the FM transmitter to 15W. The circuit includes a multi-level low-pass filter and is highly efficient. With a good antenna, the expected transmission radius is at least 20 km. It uses 2SC1972 high power RF transistor (175MHz, 4A, 25W), which must be installed on the heatsink to dissipate excess heat.
Inductors L1-L6 with 0.8 mm wire with a frame diameter of about 5 mm. If you put transistor C2538 here, the power will be even greater.
When debugging, the circuit must be connected with a load equivalent, for example a 50 Ohm 10 Watt resistor. The power source power is at least 2.5 amperes, the antenna resistance is strictly 50 Ohms. Enter the setting only with the supply voltage reduced to 9 Volts; when measuring high-frequency voltage at the antenna output, you do not need to use a conventional multimeter - there will be false readings due to interference on the device microcircuits.
300 mW VHF transmitter
The last scheme is also of interest as it is quite thoughtful and not hackneyed. Although, in principle, everything is as usual here - a generator with a power stabilizer and a high-frequency power amplifier with adjustable harmonic suppression circuits. Due to the 12-volt power supply and the 2SC2538 transistor, it was possible to obtain a range of up to a kilometer on a small helical antenna.
AM signal transmitter
The XA994 microassembly is used in radio intercoms in the high and low frequency paths of the transmitter to generate and amplify HF signals
Radio microphone
The proposed device in conjunction with a radio broadcasting
VHF FM receiver can be used for wireless
transmission of voice messages over short distances or,
for example, as a baby monitor for remotely listening to noises and sounds in a children's room. The design feature is that the LC generator coil is made in the form of a printed circuit conductor.
Radio transmitter powered by 220 V network
This circuit, with a minimum of radio components, has fairly good characteristics:
high microphone sensitivity (you can hear the ticking of the wall clock in the room),
with an antenna length of 100 cm, the range is 500 meters (when using a mobile phone with built-in FM radio).
L1 - 6 turns of copper wire, 0.5 mm in diameter
VD1 - zener diode, type KS168 (any other voltage 6.8V can be used)
VT1, VT2 - transistors, type KT315, maybe KT3102, KT368.
A correctly assembled circuit should work immediately, the entire setup consists of adjusting the frequency by compressing and expanding the turns of coil L1 and selecting resistance R7 (100 Ohm - 1 kOhm) to achieve maximum power.
C4 can be supplied with a larger capacity, in which case it will smooth out pulsations even better. The power supply should be separated from the transmitter with an aluminum screen.
Retro transmitter
The small-sized radio transmitter from Radio No. 9 - 1957 probably served as the prototype for the creation of the “toy of the 60s”. An interesting fact is that “the transmitter was also tested on the 80 and 40 meter amateur bands, where good results were obtained.” Radio amateurs who decide to repeat the design (given above or from the article published below), naturally, should not forget about the type of modulation that is in these AM transmitters ...
Simple radio microphone
The range of the radio microphone is more than 300 meters outdoors. Despite the low supply voltage, the 3V radio microphone is quite powerful, the signal is confidently pressed from it to the radio receiver across 3 floors of the building. The frequency range of the radio microphone is from 87 to 108 MHz. Radio signal reception is possible on any FM radio receiver.
The coil (L1) is 3mm in diameter, has 5 turns of copper wire with a diameter of 0.61mm. The antenna length should be half or a quarter wavelength (for 100 MHz - 150 cm and 75 cm). By changing the width of the turns of coil L1, tune the radio microphone to the range from 87 to 108 MHz.
Source - http://www.hobby-hour.com/electronics/wireless_microphone.php
Simple CW transmitter
Transmitter output power is about 1 watt. Quartz is used from the RSIU station. Coils L1 and L2 are wound directly on the resonator body, the turns ratio is 5:1. To operate in the 3.5 MHz range, coil L1 must have an inductance of 25-29 µH, and for operation in the 7 MHz range - 7-8 µH. The tap is made from 1/3 to 1/5 of the turns of L1. The circuit is tuned by C2 and the antenna is tuned by C3. The circuit can be assembled using more modern transistors KT606, KT904, etc., by reversing the polarity of the power supply.
Simple QRP CW transmitter
VHF FM low power radio transmitter
In essence, this circuit can be classified as a radio microphone with an increased range of signal reception. The device is intended
to transmit an audio signal over a certain distance, using a frequency in the VHF-FM range 88-108 MHz. In this case, signal reception is possible on a VHF-FM broadcasting receiver operating in
corresponding frequency range. It should be noted that the output power of devices for this purpose is strictly regulated and cannot exceed 0.01 W. However, when setting up and fine-tuning this circuit, it is theoretically possible to reach 0.3-0.5 W.
Simple FM transmitter
The signal from the microphone is fed to the base of transistor VT1 through the isolation capacitor C1 (10 μF). VT1 acts as an AF amplifier and at the same time as an RF generator; as a result, we receive an FM signal at the transmitter output.
L1 - determines the frequency range of the transmitter, the coil has a diameter of 7 mm, the wire diameter is 0.3...0.35 mm, the number of turns is 7, after winding the coil must be pulled out to a length of 15 mm. The collector of transistor VT1 is connected to antenna L2 (antenna), L2 has a winding diameter of 6 mm, the antenna is wound with a wire with a diameter of 0.35...0.5 mm. The antenna length is approximately 25...30cm. When winding, you should get a spring.
The transmitter range is 100 meters; when adjusting the transmitter range, compress or extend the L1 coil.
AM transmitter with a power of 25 W
Simple AM transmitter
The presented radio bug with its own hands can transmit sound over a distance of up to 500 meters. You can also use it to make an FM tuner and transmit a signal from your phone to the radio.
Radio transmitter for KT368
DIY radio transmitter for KT368
In this article I want to talk about a radio transmitter using a single transistor.
It can be used both for wiretapping, and you can also use it to make a repeater, replacing the microphone with an audio signal input.
DIY radio transmitter on MC2833
DIY radio transmitter on MC2833
Using the MC2833 chip you can make a fairly high-quality FM transmitter. This chip contains an oscillator, an RF amplifier, an audio amplifier and a modulator. Available in a miniature plastic housing with end leads for surface mounting and a standard housing.
DIY FM transmitter for 1 km and above
DIY FM transmitter for 1 km
This is a fairly powerful 2 W FM transmitter that will provide up to 10 km of range, naturally with a well-tuned full antenna and in good weather conditions, without interference. The scheme was found in the burzhunet and seemed interesting and original enough to be presented to your consideration))
DIY stereo radio transmitter circuit
DIY stereo radio transmitter
In a car, when it is not possible to turn on music from other sources like the radio, and at the same time you want to listen not only to what the radio presenters provide, but to your own music, as an option you can use the one made DIY FM stereo transmitter .
The radio transmitter is assembled in a standard plastic case from some device. The front panel has an audio jack input and a setup button. There is a power connector on the back surface. The filter output is connected to the +12V terminal, so the power cable is used as an antenna. The PCB is secured with only one screw inside the box.
Audio transmitter
DIY audio transmitter (music transmitter)
In this article I want to introduce music transmitter. I tried to assemble a radio transmitter using a varicap in the modulator. Since it was needed to transmit an audio signal and not a conversation, I installed a plug instead of a microphone. Coil of 9 turns of wire with a diameter of 1 mm, the middle tap is sealed. I pushed a small piece of foam rubber inside the coil and dripped it with paraffin (a candle) so that the coil would not bend when touched, because the frequency depends on this, and it is very easy to knock it down.
DIY stereo transmitter circuit diagram
Radio stereo audio transmitter circuit
For stereo transmitters there is specialized chip, BA1404.ABOUTfeature transmitter on BA1404 is high sound quality and improved stereo sound separation. This is achieved by using a 38 kHz crystal oscillator, which provides the pilot tone frequency for the stereo encoder.
A stereo transmitter can be used both at home and in a car to transmit sound from a storage device (phone, player, etc.), since it does not transmit stereo sound.
Such a small stereo transmitter will be a good replacement for an FM tuner.
DIY FM transmitter
FM radio transmitter
Do-it-yourself VHF-FM radio transmitter, operates in the non-traditional range of 175-190 MHz. This radio microphone is easy to assemble. In order to increase the frequency stability of the master oscillator, the base circuit of the power amplifier transistor is powered from a voltage stabilizer (R5, LED1).
Used SMD RED Light-emitting diode. The frequency drift when the power supply drops from 3 to 2.2 volts is no more than 100 KHz. When you touch the antenna with your hand, the frequency also deviates slightly. If you have a receiver with a good AFC, it tracks this change and the frequency shift does not occur at all during the operation of the transmitter.
Do-it-yourself powerful radio transmitter for 500 meters
DIY radio microphone for 500 meters
I want to present the design enough powerful radio bug, Range which amounts to 500 meters with line of sight. The device was assembled almost a year ago for my own needs. Beetle showed amazing results: The frequency hardly fluctuates (every 100 meters by only 0.1-0.3 MHz). The device does not respond to touches of the antenna and other parts (except for the circuit and the frequency-setting circuit) - this is a very important point, since almost all circuits from the Internet have such a problem.
In the practice of creating radio bugs, we often encounter the problem of the minimum possible size of a bug. Today we will talk about just such a bug: NEMESIS-2, as it was named. Nemesis was assembled on SMD components, due to which it became possible in a significant way downsize bug several times, the radio bug is so small that it will fit, for example, in one cigarette, lighter or mobile phone. A little about the parameters: frequency range within 88-108 megahertz, microphone sensitivity about 5 meters, in a quiet room you can hear the ticking of the wall clock. So this signal is easy to receive from this bug to the radio receiver, whether it’s on a phone or just a landline one. Let’s move on to the diagram and details.