Modern components allow the Amateur to make simple, but high quality signal generator for establishing equipment LW range. The description of a similar instrument German shortwave Hans Nussbaum (DJ1UGA) published in the journal "Funk" (Praeziser HF-Generator 1,6 - 30 MHz. - Funk, 2001, No. 11, S. 28-31). A diagram of this signal generator shown in the figure. It covers the frequency range of 1.6.. .30 MHz in two ranges (1,6…7 MHz and 7…30 MHz). Maximum output voltage up to 3 V (peak value) at 50 Ohms and up to 6 In with high-impedance loads. The uneven level the output signal does not exceed 2 dB across the entire operating bandwidth. Level harmonic components in the output signal is not worse than -40 dB. phase noise at offset of 25 kHz shall not exceed a level of -80 dB (relative to the level the output signal). The signal-generator consumes less than 60 mA at a voltage of 12 V.
Actually the generator is assembled at the field VT1 transistor circuit provides a small changes the output level of the generator at its the frequency within wide limits. This allowed us to cover the entire LW the range using only two sub-bands (selectable by switch SA1), and to simplify the device However, this solution requires the use constructed of the variable capacitor C1 is good Vernier device, without which it would be difficult to set the operating frequency. Moreover, for easier installation of the operating frequency at the high frequency ends of the sub-bands in the device is useful to introduce a single variable capacitor with a maximum capacity 15…30 pF connected in parallel to one of the sections of the capacitor C1. With respect to the reference operating frequency, this problem is solved using external digital frequency meter, manufacture of which does not cause ham radio problems. The supply voltage generator (8) stable integral stabilizer DA1.
High-frequency voltage with a level of about 100 mV is removed from the shutter field-effect transistor VT1 and through decoupling resistor R4 acts on the controller output signal level of variable resistor R5. The Capacitor C5 compensates for the blockage at high frequencies the frequency response of the divider formed by resistors R4 and R5+R6.
With engine resistor R5 RF voltage is supplied to a broadband integrated amplifier DA2. The mode of operation of this amplifier install setup resistor R9. For this purpose, the slider of the variable resistor R5 transferred to the upper the diagram position and adjusting the resistor R9, and achieve the lack of restrictions of the output signal. When carrying out this operation, the device output ("Output 2") should to be loaded by a resistor of 50 Ohms.
The level control, the output voltage is an RF voltmeter (R15, VD2, C12, PA1). Microammeter RA1 has full-scale deflection current of 100 μa. Frequency connected to "Output 1".
Structurally, the device is assembled on circuit Board with foil fiberglass the installation "on the patch" with a diameter of 5 mm Diodes BAR28 is a high - frequency diodes Schottky. Chip MSA0886 has performance designed for surface installation. Its direct counterpart in the larger "traditional" case - MSA0885. Such wideband amplifiers produce many foreign firms.
Author: Hans Nussbaum (DJ1UGA)