Excellent VHF receivers with your own hands. Simple and cheap do-it-yourself radio transmitter

I recently assembled a well-known FM radio circuit on a specialized k174x34 chip with simple amplifier on the TDA2003 chip, but the domestic analogue, k174un14, can also be used as a ULF.

The entire design of a homemade receiver is placed on a printed circuit board, except for variable resistors, antenna, speaker and power supply. As a case, a box was used from under the head of a JRC car tape recorder, since it is slightly longer than its counterparts in length - about a centimeter and a little deeper, which is what we need. Drawing printed circuit board download in LAY format here.

The FM receiver receives the entire range from 88 to 108 MHz. I managed to tune it to seven radio stations that switch with the smooth rotation of the “SETUP” variable resistor, but out of seven radio stations, only five have good quality, which is nevertheless very good for such a simple scheme, especially considering that the station is over 80 kilometers away.

The receiver is very loud, and especially quality sound obtained by connecting large external speakers. If you are not satisfied with the amplifier circuit, then ULF chip you can replace it with any other or remove it altogether if you listen to the radio through headphones. The antenna is a piece of meter wire, but it is better to add a small one to the circuit antenna amplifier, called UHF (amplifier high frequency).

The resistance of the resistor "VOLUME" does not have to be 33k, it can be any within 10-47k. Coils: coil L1 - frameless, 8 turns, wound on a 3mm frame with PEL wire 0.55mm. She tunes the FM receiver. L2 - input circuit, wound with the same wire, on the same diameter, only has 13 turns.

When tuning the receiver, it is necessary to stretch or compress the L1 coil until you catch the entire FM range. But do not rush to stretch it. First, try to catch stations with a fully compressed coil, as in my case. For example, I did not have to configure it at all.

The FM radio can be powered by an ordinary Chinese power supply for a landline phone or another similar one, with a current of 0.05A (in the version without VLF) or 1A (with a TDA2003 chip). The kt315 transistor can be replaced with any similar one. When assembling the circuit without errors, the receiver starts working immediately.

The VHF receiver operates in the range of 64 - 108 MHz and has a sensitivity of at least 5 μV / m. Rated voltage - 3 V. The entire high-frequency path, including the FM detector, UHF and local oscillator, is assembled on one specialized DA1 type K174XA34. This microcircuit is a UHF, mixer, local oscillator, UPCH, limiting amplifier, FM detector, noise reduction and frequency deviation compression systems, which allows the use of a low intermediate frequency - 60-80 kHz. The circuit diagram of the receiver is shown in the figure below:

The signal from the antenna is fed to the UHF through the capacitor C1. The local oscillator tuning frequency is determined by the elements L1, C4, C5, VD1. Tuning at the station is carried out by resistor R1, which changes the voltage on the VD1 varicap type KB109.

Active RC-filters on operational amplifiers are used as LPF, external elements which are capacitors C6, C8, C9, C11, C12 and C13. Signal audio frequency through the capacitor C16 enters the volume - the resistor R3. The U3CH of the receiver can be anything, including the K174XA10. Fixed resistors type MLT-0.125. Coil L1 frameless with an inner diameter of 3 mm. It has 7 turns of wire PEV 0.31.

The setting consists in laying the range by adjusting the capacitor C4.

The receiver uses two specialized chips of the K174 series. K174PS1 is a mixer and a local oscillator, and K174XA10 includes an IF path, a detector, an ultrasonic frequency converter.

The receiver operates at a fixed frequency in the range of 27 - 29 MHz. The receiver sensitivity at a signal-to-noise ratio of 12 dB is about 1 μV/m. Adjacent channel selectivity is 32 dB and depends on the parameters of the piezoceramic filter used. Selectivity on the mirror channel - 26 dB. The power of the audio frequency is 100 mW at a load with a resistance of 8 ohms. The receiver operates with a supply voltage of 4 to 9 V. The basic radio receiver is shown in the figure below:

The signal from the antenna is fed to the base of the transistor VT1, which acts as a balancing device. The circuit L1, SZ determines the selectivity of the receiver in the image channel. The amplified signal is fed to the input of the frequency converter, made on K174PS1, the frequency of which is stabilized by ZQ1 quartz. From the converter load, the intermediate frequency signal is fed to the ZQ2 piezoceramic filter, which selects an intermediate frequency of 465 kHz from a set of frequencies. The IF signal is fed to input 2 of the DA1 chip. The output stage of the IF is enabled by non-standard scheme, the role of the load of the IF is performed by the resistor R8. This somewhat degrades the quality of detection, but allows you to abandon the use of IF circuits and their settings. From the output of the detector, the audio frequency voltage is supplied at the volume R10 and from it to the power input of this microcircuit. From the UZCH output, the signal through the capacitor C13 enters the load - a loudspeaker or headphones.

All resistances in the circuit are of the MLT-0.125 type, resistor R10 is of the SP1 type. Coil L1 is wound on a ferrite rod with a diameter of 2.8 mm and a length of 14 mm and contains 16 turns of 0.23 mm PEV wire.

Resistor R8 is selected according to the minimum distortion of the sound with a minimum noise level at the output of the ultrasonic frequency converter. The circuit L1, NW is tuned to the frequency of the high-frequency signal.

Description of the K174PS1 chip can be

A diagram of a simple radio receiver on an integrated circuit K174XA10 is shown in the figure below:

As part of the multifunctional microcircuit K174XA10, there is a high frequency and a low frequency. direct gain, shown in the diagram, is equipped with an automatic AGC control system and a volume control.

The printed circuit board with the placement of elements on it is shown in the figure below:

The VHF (FM) radio receiver, assembled on a specialized KXA 058 chip, is shown in the figure below:

Greetings! In this review, I want to talk about a miniature receiver module operating in the VHF (FM) range at a frequency of 64 to 108 MHz. On one of the specialized Internet resources, I came across a picture of this module, I became curious to study it and test it.

I have a special trepidation for radios, I like to collect them since school. There were schemes from the magazine "Radio", there were just designers. Every time I wanted to assemble the receiver better and smaller. The last thing I collected was the design on the K174XA34 chip. Then it seemed very “cool”, when in the mid-90s I first saw a working circuit in a radio store, I was impressed)) However, progress is moving forward, and today you can buy the hero of our review for “three kopecks”. Let's take a closer look at it.

View from above.

Bottom view.

For scale next to the coin.

The module itself is built on the AR1310 chip. I could not find an exact datasheet for it, apparently it was made in China and its exact functional structure is not known. On the Internet, only wiring diagrams come across. Google search reveals: "This is a highly integrated, single-chip, stereo FM radio receiver. AR1310 supports 64-108 MHz FM frequency range, the chip includes all FM radio functions: low-noise amplifier, mixer, oscillator and low-drop stabilizer. Requires a minimum of external components.It has good audio quality and excellent reception quality.AR1310 does not require control microcontrollers and no additional software except 5 buttons. Operating voltage 2.2 V to 3.6 V. consumption 15 mA, in sleep mode 16 uA ".

Description and specifications AR1310
- FM frequency reception range 64 -108 MHz
- Low power consumption 15 mA, sleep mode 16 uA
- Support for four tuning ranges
- Using an inexpensive 32.768KHz quartz resonator.
- Built-in two-way automatic search function
- Support electronic regulator volume
- Support for stereo or mono mode (when closing 4 and 5 pins, the stereo mode is turned off)
- Built-in 32 ohm class AB headphone amplifier
- Does not require control microcontrollers
- Operating voltage 2.2V to 3.6V
- In SOP16 housing

Pinout and overall dimensions of the module.

Pinout of the AR1310 chip.

Wiring diagram taken from the Internet.

So I made a wiring diagram for the module.

As you can see, the principle is nowhere simpler. You will need: 5 tact buttons, a headphone jack and two 100K resistors. Capacitor C1 can be set to 100 nF, you can set it to 10 microfarads, or you can not set it at all. Capacitances C2 and C3 from 10 to 470 uF. As an antenna - a piece of wire (I took the MGTF 10 cm long, because the transmitting tower is in my neighboring yard). Ideally, you can calculate the length of the wire, for example at 100 MHz, taking a quarter wave or one eighth. For one eighth it will be 37 cm.
I would like to comment on the diagram. AR1310 can work in different ranges (apparently, for a faster search for stations). This is selected by a combination of pins 14 and 15 of the microcircuit, connecting them to ground or power. In our case, both legs sit on VCC.

Let's start assembling. The first thing I encountered was a non-standard inter-output step of the module. It is 2 mm, and it will not work to put it in a standard breadboard. But it doesn't matter, taking pieces of wire, just soldered them in the form of legs.


Looks good)) Instead of a breadboard, I decided to use a piece of textolite, assembling the usual "fly". As a result, here is the board. Dimensions can be significantly reduced by using the same LUT and smaller components. But I didn’t find any other details, especially since this is a test bench for running in.

After applying power, press the power button. The radio receiver immediately earned, without any debugging. I liked the fact that the search for stations works almost instantly (especially if there are a lot of them in the range). The transition from one station to another is about 1 s. The volume level is very high, it is unpleasant to listen to the maximum. After turning off the button (sleep mode), remembers the last station (if you do not completely turn off the power).
Sound quality testing (by ear) was carried out with Creative (32 ohm) “drop” type headphones and Philips “vacuum” type headphones (17.5 ohm). And in those, and in others, I liked the sound quality. No squeakiness, enough low frequencies. A music lover from me is useless, but the sound of the amplifier of this microcircuit was pleasantly pleased. In Phillips, I could not unscrew the maximum volume, the sound pressure level was painful.
I also measured the current consumption in sleep mode 16 μA and in working 16.9 mA (without connecting headphones).

When connecting a load of 32 ohms, the current was 65.2 mA, with a load of 17.5 ohms - 97.3 mA.

In conclusion, I will say that this module radio receiver is quite suitable for domestic use. Even a schoolboy can assemble a ready-made radio. Of the "minuses" (rather not even cons, but features), I note the non-standard pin-to-pin pitch of the board and the lack of a display for displaying information.

I measured the current consumption (at a voltage of 3.3 V), as we see, the result is obvious. At a load of 32 ohms - 17.6 mA, at 17.5 ohms - 18.6 mA. This is a completely different matter!!! The current changed slightly depending on the volume level (within 2 - 3 mA). I corrected the diagram in the review.