Device for tuning 465 kHz IF circuits. Radio circuits and electrical circuit diagrams. Narrowband sweep source

The IF generator is assembled on element DD1.4. Its feedback circuit includes a circuit formed by an inductor, capacitors C1 - C4 and a varicap VD2. Two control voltages are supplied to the varicap, one of which is constant (supplied through R1 - R4) and determines the central frequency of the generator, and the second is sawtooth (supplied through R17C6), it determines the swing band.
The center frequency is switched by changing the inductors L1 and L2 with switch SA1. This is done in order to simplify the setup of the device and make a single scale for resistor R17.
From the capacitive divider C2 and C3, part of the voltage of the IF generator is supplied to a buffer stage on transistor VT2, at the output of which a smooth (R16) and step regulator (R19 - R21) of the output voltage are installed.
The following parts can be used in the design: microcircuits - K176LE5, K561LA7, K176LA7; transistors - KT315, KT312, KT3102 with any letter indices; diode VD1 -KD509, KD521A, KD522B, D220, D223; varicap - KB104A-KB104E, KB119A; capacitor C9 - K50-3, K50-6, K53-1, the rest - KLS, KM, KT; power switch - P2K, MT1; resistors R2, R16-R18-SP, SPO, SP4-1, R5 -SP3-3, the rest - BC, MLT. The coils are wound on frames from the IF coils of the Alpinist-407 radio receiver and contain 350 (L1) and 310 (L2) turns of PEV-2 0.08 wire, multilayer winding.
Most of the generator parts are placed on a printed circuit board made of foil PCB. All variable resistors, fixed resistors R19 - R21, capacitors C7 and C9, as well as output sockets and switch Q1 are located on the front panel.
Setting up the device comes down to calibrating the scales of resistors R2 and R17 and setting the required sawtooth voltage shape. To do this, first connect an oscilloscope (Rin = 1 MOhm) to the output of element DD1.3 and use resistor R5 to achieve an undistorted “saw” shape. Changing its amplitude is performed by selecting the resistance of resistor R9. The “saw” frequency can be changed by selecting the capacitance of capacitor C5.
Then a frequency meter is connected to the output of the IF generator, resistor R2 is set to the middle position, and R17 to the bottom (according to the diagram). Using the magnetic circuit of coil L1, the frequency is set to 465 kHz, and L2 - 500 kHz, then the scale of resistor R2 is calibrated in both subranges and, if necessary, by selecting resistors R1 and R3, the required tuning range and its symmetry with respect to the central frequencies are achieved.
Then the scale of resistor R17 is calibrated. To do this, the synchronization voltage is supplied to the X input of the oscilloscope from the XS1 socket of the IF generator, and to the Y input of the oscilloscope - a signal from the XS4 socket ("IF Output" 1:10) of the IF generator and through a 100 Ohm resistor from a standard high-frequency generator, which is used as reference Resistor R18 sets the sweep length to the width of the entire oscilloscope screen. After this, by rotating resistor R17 and changing the frequency of the reference oscillator, the scale of resistor R17 “Swing Band” in kHz is calibrated according to the zero beats on the oscilloscope screen.
The IF generator should be powered from a stabilized source with a current of at least 20 mA.

I. NECHAYEV, Kursk, Radio No. 9, 1993, p. 20

Homemade devices

I. NECHAYEV, Kursk
Radio, 2000, No. 8

Radio receiving paths various equipment (radio receivers, radio tape recorders, CB transceivers, etc.) contain similar components such as audio frequency amplifiers (3F), intermediate frequency amplifiers (IF) of FM and AM stations. They have to be checked first when repairing equipment. The one offered here will help with this. probe generator.

This relatively simple device provides the generation of 3F control signals with a frequency of 1 kHz and modulated IF signals with a frequency of 10.7 MHz and 465 (or 455) kHz. The amplitude of each signal can be smoothly adjusted.

Device diagram

The basis of the device (Fig. 1) is a generator based on transistor VT1. Its operating modes are set by switch SA1. In the position shown in the diagram ("3H") of the switch, the supply voltage of the battery GB1 is supplied through resistor R9 to the transistor and the generator begins to operate at a low frequency. It is determined by the frequency-setting chain R2C3R3C4R5C5 in the feedback circuit of the transistor.

In the switch position “465”, the supply voltage is supplied to the transistor through resistor R10, at the same time diode VD1 opens and filter ZQ1 is turned on in the feedback circuit of the transistor cascade. Generation occurs at 3H (1 kHz) and AM IF frequencies (approximately 465 kHz), while modulation of the IF signal by the 3H signal occurs at the same time. Filter R1C1 eliminates high-frequency feedback through capacitors SZ-C5, ensuring stable operation of the generator on the inverter.

When the switch is set to position "10.7", the supply voltage to the transistor is supplied through resistor R11. Diode VD2 opens, and filter ZQ2 is included in the feedback circuit. The generator will operate at 3H (1 kHz) and FM IF (approximately 10.7 MHz) frequencies. The IF signal is modulated by a 3H signal.

The generated signals through resistor R12 and capacitor C8 are sent to the output voltage regulator R13, and from its engine to the output sockets X1 and X2.

In the "Off" switch position the power source is disconnected from the generator.

In addition to what is indicated in the diagram, transistors KT3102A-KT3102D, KT312V can be used in the device. Filter ZQ1 - any of the FP1P-60 series, preferably a narrower one. At a frequency of 455 kHz, a foreign-made filter should be used. Filter ZQ2 - bandpass piezoceramic at a frequency of 10.7 MHz, domestic (for example, FP1P-0.49a) or similar imported. Capacitors - K10-7, K10-17, KLS or small imported ones. Trimmer resistor R2 - SPZ-1b, variable resistor R13 - SPO, SP4, the rest - MLT, S2-33. Switch - any small-sized switch with one direction and four (or more) positions. Power source - voltage 4.5... 12 V. This can be series-connected galvanic cells, batteries, a Krona battery, or a source of the structure being tested.

Most of the parts are placed on a printed circuit board (Fig. 2) made of one-sided foil fiberglass.

It is placed in a plastic case of a suitable size, on which a variable resistor R13 and sockets X1, X2 are installed (Fig. 3). A probe is inserted into one of the sockets, depending on which components are being checked. The common wire is brought out through a hole in the housing and equipped with an alligator clip. If the power supply is built-in, it is necessary to provide space for it in the housing. Installation of capacitors C7, C9, SY is carried out using the hinged mounting method.

Instead of a filter at a frequency of 465 kHz, you can put a filter at 455 kHz - then the generator will operate at this frequency. It is permissible to use a five-position switch and additionally enter this frequency. The new filter must be turned on in the same way as ZQ1. If external power is planned, a new frequency can be set using the vacant switch contact.

The device must be configured at the voltage with which it will operate. Current consumption is within 0.5...3 mA depending on the supply voltage.

Then they check the generation in the switch position “465” (or “455”) and by moving the slider of the resistor R2 achieve stable generation of 3F and IF signals at the switch positions “465” (“455”) and “10.7”. If the generation is unstable in the “3H” position, you will have to select resistor R9.

The probe is used as usual, sending signals to certain points of the device being tested.

Homemade measuring instruments

A. SLINCHENKOV, Ozersk, Chelyabinsk region.
Radio, 2002, No. 12

The radio receiving equipment contains paths 3Ch and IF, and the IF frequencies have different values: 455 kHz - in imported and 465 kHz in domestic AM signal receivers; 5.5, 6.5 and 10.7 MHz - in FM signal receivers. The magazine "Radio" has already published circuits of generator-probes for testing 3Ch and IF paths. As a rule, they produce two signals - 3F and a modulated IF signal with one of the named frequencies. To avoid having to make several probes, the proposed generator provides frequency switching. It's suitable to check radio receiving equipment, including the sound path of televisions.

Device diagram

The audio frequency generator is assembled on transistor VT1 according to a circuit with a phase-shifting RC circuit (capacitors C1 - C4 and resistors R1 - R3). The emitter follower on transistor VT2 decouples the generator from the load - the RF generator. The latter is made on transistor VT3. Instead of resonant LC circuits, the generator uses small-sized piezoceramic IF filters ZQ1 - ZQ5 from radios or TVs. The filter corresponding to the desired IF is selected by switches SA1 (FM or AM) and SA2 (specific IF value). In the 3H position, no filter is turned on and the RF generator does not work. In this case, only the 3H signal is output.

The modulated RF signal is supplied to the output emitter follower, assembled on a VT4 transistor, which significantly weakens the influence of the load (the units being tested) on the RF and 3F generators. Variable resistor R8 sets the required output signal level. Separating capacitors C7 and C8 at the generator output are switched by button SB1. In the position of switch SB1 shown in the diagram, only modulated RF signals pass through capacitor C7 of a relatively small capacitance. When switches SA1 and SA2 are set to position “34”, use button SB1 to connect high-capacity capacitor C8. Power is supplied to the probe from the power circuits of the equipment being tested. The supply voltage can range from 3 to 12 V.

The probe generator is assembled on a board made of getinax or fiberglass. The location of parts and connecting conductors are shown in Fig. 2.

To enlarge, click on the image (opens in a new window)

If the board is made of foil material, then a printed circuit board can be made from the drawing. After manufacturing, the board is placed in any suitable housing, for example, from the GSP-1 grid field generator.

Transistors VT1 - VT4 can be replaced with KT3102 or KT312 with any letter index; it is advisable to select transistors VT2 and VT3 with the highest current transfer coefficient. Any piezoceramic filters from domestic or imported equipment with suitable frequencies are suitable for the HF generator.

Switch SA1 is used type PD9-1, SA2 - PD21-2, button SB1 - MP-7 or other small-sized. All resistors are MLT-0.125 (MLT-0.25 is also possible), capacitors are KD, KM, K10 or other small ones. Resistor R8 - SPO-0.15 or SP-3-386. The output contact X1 is a needle soldered to a pad on the board (on the right in Fig. 2), and contact X2 is a wire with an alligator clip soldered on the end of it.

Setting up the probe generator begins with setting the mode of transistor VT1. Its collector voltage should be 1.5 V with a supply voltage of 3 V. To set the collector voltage, resistor R4 is selected. After this, the presence of generation is checked when the supply voltage changes from 3 to 12 V. Then the SZ capacitor is unsoldered (the 3Ch generator stops working), a supply voltage of 3 V is applied, and by selecting resistor R7, RF generation occurs at all fixed frequencies, i.e. when connecting any piezoceramic filter. If generation does not occur in any of the positions of switches SA1 and SA2 (most often this happens in position “10.7”), select resistor R6 and then again check the operation of the RF generator at all frequencies.

You can verify the presence of RF generation by connecting a high-frequency oscilloscope, millivoltmeter, a simple detector with a measuring head, or a frequency meter to the probe output. In the latter case, the generation frequency is also checked. Then install the SZ capacitor in place and, if you have an oscilloscope, check the quality of the RF signal modulation.

Working with the probe is simple. If a 3H amplifier is being tested, switches SA1 and SA2 are set to the “3H” position, press the SB1 button and apply the 3H signal with probe X1 alternately to the various stages of the amplifier being tested, not forgetting to set the required signal level with resistor R8. When checking the amplifier of various equipment, select the required frequency value using switches SA1 and SA2; do not press the SB1 button. By applying a signal to the input of the amplifier, first after the main selection filter, and then before it, one is convinced that the signal passes through the filter and the amplifier. Otherwise, the UPC is checked in cascade

LITERATURE
1. Malinovsky D. Frequency synthesizer for the 144 MHz range. - Radio, 1990, No. 5, p. 25.
2. Titov A. Probe... - a generator for testing radio receivers. - Radio, 1990, No. 10, p. 82.83.
3. Nechaev I. Probe-generator for checking the radio receiving path. - Radio, 2000, No. 8, p. 57.

When repairing an audio amplifier or household radio at home, it often becomes necessary to trace the passage of the signal through the cascades. And this causes certain difficulties during repairs for radio amateurs who do not have the necessary equipment.
The simple generator-probe we bring to your attention is designed for repairing radio equipment. It does not contain winding units and can be manufactured, configured and operated even by a novice radio amateur. The probe generator allows you not only to check the serviceability of the audio amplifier and the intermediate frequency amplifier circuit (IF 465 kHz) of the radio receiver, but also to adjust the IF circuits of the radio receiver to the maximum signal level. The schematic diagram of the device is shown in Fig. 1.
A low-frequency generator is assembled on transistor VT1, producing oscillations with a frequency of approximately 1 kHz (determined by the parameters of the phase-shifting circuit C1C2C3R1R2 included in the OOS circuit).
The output signal is fed to the base of the RF generator VT2 through a single-stage low-pass filter R5C5, which cleans the output signal from harmonics and reduces its amplitude to obtain an AM modulation depth of approximately 30%.
The high-frequency generator operates at a frequency of 465 kHz and is made according to a three-point capacitive circuit (Clapp version), only instead of an inductor, a ZQ1 ceramic resonator is used. In this circuit, generation of oscillations is possible only with inductive reactance of the resonator circuit, i.e. the oscillation frequency is between the frequencies of series and parallel resonances. A small-sized ceramic filter FP1P1-61-02 (marking without color marks) was used as a resonator.
Filters series FP1P1-61 widespread, inexpensive and, most importantly, when switched on as indicated in the diagram, they have a small spread of parameters over the generation frequency. I tested my existing batch of 7 pieces and I want to note that the actual spread in the generation frequency did not exceed +-0.5 kHz (according to the specifications it should not exceed +- 1 kHz). That. When using virtually any filter from the FP1P1-61 series, it is guaranteed, without adjustment, to obtain a test signal with a frequency of 465+-1 kHz, which is what we actually need. The VT2 emitter is loaded onto a resistive divider R7R8, which reduces the output signal to practical levels and ensures stable operation of the generator regardless of the connected external circuits (device under test). Potentiometer R9 is used to smoothly adjust the output signal level.
With the switch positions indicated in the diagram, the output of the generator-probe will be an AM signal with a frequency of 465 kHz, modulated by a low-frequency signal of 1 kHz (30% modulation). Moreover, if you turn on SA1, then only a 465 kHz unmodulated IF carrier signal will appear at the output, if you turn on SA2, then only a low-frequency signal with a frequency of 1 kHz will appear at the output.
You can use any HF transistors (KT315, KT3102, BC847, 2N2222, etc.) with H21e in the range of 100-220, otherwise you will need to select R4 to obtain 4.5+-0.5V at the collector VT1.
Powered by Krona, installation can be in any way available to you - on a breadboard, signet or mounted.

HF generator

The proposed RF generator is an attempt to replace the bulky industrial G4-18A with a smaller and more reliable device. Usually, when repairing and setting up HF equipment, it is necessary to “lay” HF bands using LC circuits, check the signal passage along the RF and IF paths, adjust individual circuits to resonance, etc. Sensitivity, selectivity, dynamic range and other important parameters of HF devices are determined by circuit design solutions, so it is not necessary for a home laboratory to have a multifunctional and expensive RF generator. If the generator has a fairly stable frequency with a “pure sine wave”, then it is suitable for a radio amateur. Of course, we believe that the laboratory’s arsenal also includes a frequency meter, an RF voltmeter and a tester. Unfortunately, most of the tested HF generator circuits in the HF range produced a very distorted sine wave, which could not be improved without unnecessarily complicating the circuit. The RF generator, assembled according to the circuit shown in Fig. 1, has proven itself very well (the result is an almost pure sine wave throughout the entire HF range)

This design uses a variable capacitor type KPV-150 and a small-sized PM range switch (11P1N). With this KPI (10...150 pF) and inductors L2...L5, a section of the HF range of 1.7...30 MHz is covered. As work on the design progressed, three more circuits (L1, L6 and L7) were added to the upper and lower sections of the range. In experiments with KPIs with a capacitance of up to 250 pF, the entire HF range was covered by three circuits.

The RF generator is assembled on a printed circuit board made of foil fiberglass laminate with a thickness of 2 mm and dimensions of 50x80 mm. The tracks and mounting spots are cut out with a knife and a cutter. The foil around the parts is not removed, but is used instead of “ground”. In the figure of the printed circuit board, for clarity, these sections of the foil are not shown.

The entire structure of the generator, together with the power supply (a separate board with a 9 V voltage stabilizer according to any circuit) is placed on an aluminum chassis and placed in a metal case of suitable dimensions. The front panel displays a range switch knob, a KPI adjustment knob, a small-sized RF connector (50 Ohm) and an LED indicator for powering on. If necessary, you can install an output level regulator (variable resistor with a resistance of 430...510 Ohms) and an attenuator with an additional connector, as well as a graduated scale. Unified sectional frames of the MF and DV ranges from obsolete radio receivers were used as the frames of the circuit coils. The number of turns of each coil depends on the capacity of the KPI used and is initially taken “with a reserve”. When setting up ("laying" the ranges) of the generator, some of the turns are unwound. Control is carried out using a frequency meter. Inductor L7 has a ferrite core M600-3 (NN) Ш2.8x14. Screens are not installed on circuit coils. The winding data of the coils, the boundaries of the subranges and the output levels of the RF generator are given in the table.

In the generator circuit, in addition to the indicated transistors, you can use field-effect ones KP303E(G), KP307 and bipolar RF transistors BF324, 25S9015, BC557, etc. Coupling capacitor C5 with a capacity of 4.7...6.8 pF - type KM, KT, KA with low RF losses. It is advisable to use high-quality ones (on ball bearings) as KPIs. With rigid installation, high-quality parts and warming up the generator for 10...15 minutes, you can achieve a frequency drift of no more than 500 Hz per hour at frequencies of 20...30 MHz. The signal shape and output level of the manufactured RF generator were checked using an S1-64A oscilloscope. At the final stage of setup, all inductors (except L1, which is soldered at one end to the body) are fixed with glue near the range switch and KPI.

Wideband generator

The range of generated frequencies is 10 Hz-100 MHz

Output voltage - 50 mV

Supply voltage - 1.5 V

Current consumption - 1.6 mA

Printed circuit board and front panel

Appearance

Simple RF Generator

To set up high-quality receiving equipment, you need an RF signal generator. The figure shows a diagram of such a generator operating in two ranges 1.6-7 MHz and 7-30 MHz. Smooth adjustment - three-section variable capacitor C1 with an air dielectric.

Schottky diode VD1 serves to stabilize the output RF voltage over a wide frequency tuning range.

Maximum output voltage 4 V, variable adjustableth resistor R4.

Coils L1 and L2 are wound on ferrite rods 2.8 mm long and 12 mm long from 100HH ferrite. L1 - 12 turns of PEV 0.12, L2 -48 turns of PEV 0.12. Winding is ordinary. Coil L3 is wound on a 7 mm ferrite ring, a total of 200 turns of PEV 0.12 in bulk.

HF generator