Sweep frequency generator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Measuring technology
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The figure shows a diagram of a swept frequency generator for the range of 3-30 MHz. It consists of two high-frequency generators. One of them, made on the transistor T1, generates a signal whose frequency within 83-113 MHz can be changed by a variable capacitor C3. The second generator (variable frequency) is assembled on a transistor T2 and a varicap D1.
(click to enlarge)
In the absence of a control voltage on the varicap, the generator is tuned to a frequency of 80 MHz. The sawtooth control voltage with a frequency of 35 Hz is supplied to the varicap from a sawtooth voltage generator made on transistors T5 and T6. The optimal voltage shape is set by selecting resistors R17, R18.
The linearization of the sawtooth voltage is achieved by using a unijunction transistor T6 and a current stabilizer (transistor T5), through which the capacitor C13 is charged. The source follower on transistor T4 is a buffer stage between the sawtooth voltage generator and the amplifier on transistor T3.
The signals from the RF generators are fed to the mixer (transistor T1). The resulting difference frequency signal through the buffer stage (emitter follower on the transistor T8) is fed to the transistor T9 and through the variable resistor R32 is fed to the device under test. The signal from the output of this device through the source follower (transistor T10) is fed to the measuring device (oscilloscope). The cascade on the transistor T10 eliminates the influence of the measuring device on the device under test.
The frequency deviation is set by a variable resistor R10. The level of the signal to the device under test is regulated by a variable resistor R32.
The GKCh consumes a current of about 15 mA from the lithium source. Coils L1 and L2 are frameless, with an outer diameter of 6 mm. They contain 0,71 turns of enameled wire with a diameter of 6 mm. On the MCC circuit board, points A and XNUMX should be placed as far apart as possible.
Transistors 2N2222 and 2N918 can be replaced by transistors of the KT315 series. 2N706 - on KT603A, and BC350 - on KT352 with any letter index. Instead of transistors TIS34 and 2N5459, we recommend using KP302A, and instead of 2N1671B - KT117. Varicap must be selected from the D901 series.
Literature
- "OLd man" (Switzerland), 1975, No. 1
Publication: N. Bolshakov, rf.atnn.ru
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