The proposed generator operates in the frequency range from 26560 kHz to 27620 kHz and intended for setting up NE-equipment. The voltage signal " Output. 1 " is 0.05 V on 50 Ohm load. There will be a "O.2". to which you can connect a frequency counter when establishing receivers. The generator provides the possibility of obtaining a frequency-modulated oscillations. For this is "BX. mod.", served on the low-frequency signal from an external generator of sound frequency. The power generator is supplied from a regulated source of +12 V. the current consumption does not exceed 20 mA. The master oscillator is made on field-effect transistors VT1. VT2. included on a "common source - common gate".
The generator, collected under the scheme, works well at frequencies from 1 to 100 MHz. because it employs field-effect transistors with a cutoff frequency >100 MHz. According to studies [1]. this generator has a short-term frequency stability (for 10 s) better than the generators made by schemes of capacitive and inductive treatacne. Care of the oscillator frequency for every 30 minutes of operation after a two-hour warm-up, and the levels of the second and third harmonics is less than that of the generators, made by the scheme of treatacne. Positive feedback in the oscillator is a capacitor C10. In the chain gate VT1 is connected resonant circuit...C5 C8. L1. determining the frequency of oscillation of the circuit.
Through a small capacitance C9 is connected to the circuit Maricopa matrix VD1. Feeding the low-frequency signal, changing its capacitance and thereby carried out by frequency modulation of the generator. The power generator is additionally stabilized VD2. The high frequency signal is removed from the resistor R6. included in the source circuit of the transistors. To the generator through a capacitor 11 connected broadband emitter follower on VT3 and VT4. The advantages of such a repeater is given in [2]. To its output through a capacitor 15 is connected to a voltage divider (R14.R15). Output impedance on the "new.1" equals 50 Ohms. therefore, using a coaxial cable with a characteristic impedance of 50 Ohms to be connected to a circuit with an input impedance of 50 Ohms. for example, RF attenuator, published in [3]. To the output of the emitter follower source follower connected to VT5. This enabled us to eliminate the mutual influence of loads. connected to the "new.1 and O.2".
Details. Capacitors C6 C10... - type CT. The remaining capacitors: ceramic - type K10-7V. K10-17. electrolytic - type K50-35. Coil L1 is wound on a ceramic ribbed frame (the size of the ribs 15 mm) silver plated wire with a diameter of 1 mm with a step of 2 mm. the Number of turns -- 6.75. The winding is performed by heated wire with "tightness". The inductor L2 from the black and white tube TVs (you can use other) inductance from 100 to 300 µh. Resistors - type MLT-0.125. FETs can use any from KB. even better - from KB. High-frequency connectors X1...XS - type SR50-FW. Transistor VT3 - any high frequency npn-type. VT4 - high frequency pnp-type.
Configure. In some instances field-effect transistors of possible spurious relaxation and intermittent high-frequency generation. This requires the selection of resistor R6 and capacitor C10. To obtain the minimum value of temperature coefficient of frequency is necessary to select the capacitor C8 C6.... both positive and negative TKE based conclusions. done in the paper [4]. The generator must be placed in a shielded enclosure made of brass or foil fiberglass. This high frequency generator has only one point of switching, when switching ranges, so it is easy to perform on several ranges. The calculation of the oscillation circuit to other ranges can be performed according to the method. given in [5].
Literature
1. Kotanko D.. N. Turkin. LC-oscillator FET. Radio. 1990. No. 5. S. 59.
2. Broadband a voltage follower. Radio. 1981. No. 4. S. 61.
3. RF attenuator. - Ham. LW and УSW. 1996. No. 10. S. 36.
4. Mukhin, V. Nonstandard behavior of inductors when heated. -- Hams. 1996. No. 9. p. 13. 14.
5. Maslov E. Calculation of the oscillatory circuit to a stretched configuration. - Ham, 1995. No. 6. pp. 14-16.
Author: Oleg Belousov, Ukraine, Cherkassy region, Vatutino; Publication: N. Bolshakov, rf.atnn.ru