SK-219 regenerated short wave radio, Short Wave Radio
Keywords: SK-219 regenerated short wave radio
Short-wave broadcasting is transmitted by electroplating layer reflection signal, so it is farther than the distance between medium wave broadcast transmission. The short-wave radio is our understanding of world information, training foreign language listening, and makes a favorable tool for remote radio reception. The short-wave radio can be divided into two categories from the circuit program: direct enlargement and overaltural difference. The regenerative short-wave radio design of the company is directly enlarged, and the regenerative circuit is used, which has greatly improved its sensitivity and selectivity. It has the simple circuit of simple, excellent performance, and easy to make commissioning. It is very suitable for beginners.
Circuit work principle
The company's designed regenerative short-wave radio can receive a short-wave broadcast station with a frequency range of 4.5 to 13 MHz, divided into SW1 and SW2 two bands. 1 is a circuit diagram of a regenerated short-wave radio, FIG. 2 is a block diagram thereof.
SK-219 circuit schematic (Figure 1) SK-219 block diagram (Figure 2)
The circuit consists of the following parts:
The receiving antenna L1 and the variable capacitor C1 constitute a tuning loop, and its function is to receive and select a short-wave broadcast station signal.
The first high frequency magnitude of the field effect triode VT1 and the like;
Transistor Vt2 or the like constitutes a second high frequency amplification; two high places are directly amplified by radio signals selected by the tuning circuit.
Capacitor C3, etc. constitutes a regenerative circuit, further improving the sensitivity and selectivity of the radio.
Diode VD1, etc. constitutes a detection circuit, and the audio signal of the modulation is detected on high frequency carrier waves.
The low frequency power amplifier composed of integrated circuit IC1 and the like, enlarges the audio signal and pushes the speaker BL voice.
Regenerative short-wave radio brief working principle is:
After the high-frequency signal transmitted by the radio station is received by the antenna L1, the required radio signal is selected from the L1, C1 parallel resonance circuit, and the variable capacitor C1 is adjusted to generate resonance in the parallel resonance circuit with a radio signal that needs to receive. That is to achieve the destination. S1 is a band switch. When S1 points to SW1, the C1a, C1b is accessed, and the received range is 4.5 to 6.5 MHz; when S1 points to SW2, only the C1A access circuit is only 6.5 to 13 MHz.
The tuning circuit is selected to be sent to the VT1 base. The two-stage high frequency amplifier is performed by VT1, VT2, and the amplified signal is in phase of the input signal. The VT2 collector output is output, and the C6 is coupled to the detection circuit; another Aspect is fed back by C3 to the VT1 base, so that the high frequency signal of the high amplifier input is further enhanced, and the strengthened signal is enlarged by the two-stage high amplifier, and it is incorporated into the input terminal, so that the input signal is greatly improved. Strengthened, this is the so-called "regeneration". The strength of the regeneration can be adjusted by the potentiometer RP1. The first high velocity VT1 adopts the field effect transistor with extremely high input impedance, which facilitates improving the magnalectic performance and the Q value of the tuning circuit, thereby improving the sensitivity and selectivity of the radio.
After the high frequency signal output from the C6, after the VD1 detection, C7 is filtered out of the high frequency component, the audio signal is coupled to the integrated circuit IC1 to the integrated circuit IC1, then output to the speaker BL (or transferred by the socket X1) via C10 earphone). RP2 is the volume adjustment potentiometer.
The whole machine is powered by a 6V battery, C12 to C14, and R4 to form a decoupling circuit to prevent harmful coupling due to the internal resistance of the battery. The regulator diode VD2 provides voltage stability to high gradation, further increasing circuit stability.
Component selection and identification
The variable capacitor C1 uses a small double connection, its antenna connection (150pF) is C1a, which is oscillated (80pf) to C1B, see the figure above
D1 uses 1N60, VD2 uses 5.6V stabilizing tube, and their positive and negative is very elegant.
T1 adopts the field effect transistor K161, VT2 adopts a PNP transistor 9015, and their pins are shown above.
C1 uses audio power integrated circuit LM386, each pin location is shown above
Commissioning and use
After the cyclic antenna is connected, the radio is loaded, and the volume potentiometer RP2 is rotated to about 3/4 position (the power switch S2 is turned on), and the regeneration adjustment potentiometer RP1 is placed in the intermediate position, the rotation tuning knob (C1) Until the scream (is a broadcast radio station signal), then slowly returning RP1 to reduce the regenerative strength until the screams have disappeared, and the radio broadcast is heard. Repeated adjustment tuning knob and regeneration knob make the sound clearer, and adjust the volume size at any time as needed. When there is condition, the frequency scale can be calibrated with a signal generator (or a station with known frequencies). First place in the SW2 wave section, adjust the C1A fine tuning capacitor, enabling the frequency indication to match the received signal frequency; placed in the SW1 band, adjusting the C1B fine tuning capacitor, enabling the frequency indication to match the received signal frequency.
Since the short-wave signal is revealed by the ionization layer, it is affected by the season, day and night, and climate change. The better time to receive a better time in the morning and dusk to midnight, you can receive records, accumulate experience, master the local law, and continuously improve the listening skills, this process is fun for radio enthusiasts.
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