Device for testing quartz resonators. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Measuring technology

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The design proposed for repetition by radio amateurs is intended for testing quartz and piezoceramic resonators, as well as a controlled frequency generator up to 80 MHz.

A master oscillator is built on the DD1 integrated circuit of the KR531GG1 type. This microcircuit consists of two controlled oscillators, the frequency of which is set by quartz, piezoceramic resonators or capacitors connected to its outputs C1, C2. This device uses only one generator of this chip. Resistor R1 connected to terminals C2, C1 facilitates the start of an oscillator with resonators with an operating frequency of less than 4 MHz. All tested resonators will be excited at the fundamental resonance frequency - the first harmonic.

This should be taken into account when checking resonators intended for operation in radio receivers and radio transmitters. For example, 27 MHz harmonic crystals (third harmonic) will be excited at 9 MHz. A frequency divider by 2 and 2 is assembled on the DD4 chip. The high-frequency signal from the output F DD1.1 through the resistor R1 is fed to the input C of the D-trigger DD2.1, the frequency divider is turned on by 2, from the output of this trigger a signal with a frequency of half the frequency the master oscillator is supplied to the second D-flip-flop DD2.1, included in a similar way. As a result, at the output of the frequency divider, a signal is obtained with a frequency 4 times lower than the frequency of the master oscillator. LED HL2 signals with its glow that the tested resonator is excited. Chip DD3 is used as buffer elements, which eliminates the influence of the connected load on the stability of DD1, DD2.

A frequency counter capable of measuring signals with a frequency of at least 80 MHz can be connected to the frequency control device. A signal can be applied to the frequency meter both at the frequency of the DD1 master oscillator, and at a frequency of half or four times less, which can be useful when using a remote probe of the frequency meter and a connecting cable with insufficient bandwidth. All integrated digital circuits used are powered by a stable voltage source built on the DA1 stabilizer. When the generator is excited at a frequency of 48 MHz, the device consumes a current of about 90 mA from the power source. LED HL1 indicates the presence of supply voltage. Diode VD1 protects the device from supply voltage of reverse polarity.

In the author's version, the elements are mounted in a hinged way with a thin mounting wire, while the entire foil layer is used as a common wire. It should be noted that the wiring of power circuits and signal circuits requires accuracy and understanding, since the microcircuits of the KP531, 74F series are very high-frequency and, if installed unsuccessfully, can generate interference with a wide frequency spectrum.

Details

Instead of the KR531GG1 chip, you can use KR1531GG1, K531GG1P. Perhaps there is an imported analogue from the 74F124N series. The imported MC74F74N chip can be replaced by any of the 74F74N series or the domestic KR531TM2. By slightly changing the circuit diagram, you can install a divider by 10 in place of this microcircuit, for example, assembled on the KR531IE9, 74F160N microcircuit with any prefix. You can use other TTL or CMOS frequency dividers that can operate at a frequency of at least 80 MHz at a supply voltage of +5 V. The MC74F00N chip can be replaced by any of the 74F00N series or domestic KR531LAZ, KR1531LAZ. When using domestic microcircuits, the current consumed by the device may increase slightly. If you fail to purchase such microcircuits, then you can temporarily install the corresponding microcircuits of the KR2 series instead of DD3 and DD1533, while the operating frequency range of the device will decrease to 50 ... 70 MHz.

Instead of an integral stabilizer for a fixed output voltage of +5 V of the L7805ACV type, you can install any of the 7805 series in the TO-220 package or the domestic IC KR142EN5A, KR142EN5V. When using some stabilizers, the lower limit of the minimum supply voltage can increase from 7 V to 8 V. The voltage regulator chip is installed on a small heat sink. Diode 1N4001 can be replaced by any of the series 1 N4001-1 N4007, KD243, KD226. Instead of diodes 1N4148, diodes of the KD503, KD409, 2D419 series are suitable. LEDs are suitable for any type of general application.

Oxide capacitors K50-35, K53-19, K53-30 or imported analogues. Non-polar capacitors - ceramic K10-17 or similar imported ones. Resistors of any type are small-sized, for example C1-4, C2-23, MLT. To test resonators with different lead diameters, two different panels are installed. The length of the conductors from the conclusions C1, C2 DD1 should be as short as possible. If, instead of the ZQ1 resonator, a small-sized variable capacitor with a capacity of 20 ... 540 pF is connected to the sockets, then the generator frequency can be changed from 12 MHz to 760 kHz.

The device can be improved if a frequency-setting capacitor is connected in place of ZQ1, input E DD1.2 is connected to a common wire, output F DD1.2 is connected to input Ud or Uc DD1.1, a capacitor with a capacity of 12 is connected to pins 13 and 1 of DD0,22 uF. After all this, the DD1.2 generator will operate at a frequency of 2 kHz, and at the output F DD1.1, pin 7, there will be a frequency modulated signal. In addition, anti-phase modulating signals can be simultaneously applied to the inputs Ud, Uc, for example, from the output F DD1.1 and the output of the inverter DD3.1. To reduce the frequency deviation, modulating signals can be fed through trimmers with a resistance of 220 ... 470 Ohms.

Not only quartz or piezoceramic resonators can be used as resonators, but also piezoceramic filters, such as an oscillator, are very well excited with 10,7 MHz filters from VHF radios. The device can be used not only to test resonators, but also as a calibrator, microtransmitter, sound effects generator, capacitor capacitance meter. The scope of the KR531GG1 microcircuit is not limited only to the options described in this article, but the cheapness and availability of this microcircuit allows you to conduct many experiments with it, which contributes to the diversity of amateur radio everyday life and the expansion of interests.

Author: A.L. Butov, p. Kurba, Yaroslavl region; Publication: cxem.net

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