Fullband receiver with TA7358 mixer, TA7358 Receiver
Keywords: full-piece receiving head composed of TA7358 mixer
Full-pack receiving head composed of TA7358 mixer
At present, the full-band frequency modulation header introduced by various magazines is dazzling, but most receiving head mixers use special mixing circuits NE602. This article introduces the full-band receiving head of the low voltage supply of the mixer by the TA7358, the receiving head is high, the performance is stable, easy to obtain all of the frequency modulation signals of 45 ~ 870MHz, can be used to listen to FM broadcasts, television sound And signals such as walkie-talkies and cordless phones.
The principle of circuit is shown in the figure. The high-frequency signal received from the antenna is enlarged and the 31.5MHz sound intermediate frequency signal generated after the high frequency head is outputted by the IF end. After the first stage 2SC3355 is zoomed, it enters the IC11 foot, and it is once again enlarged by IC1. Mixed with 42.2MHz, generate 10.7MHz second intermediate frequency signal, which is sent to IC2 (15) foot, released by IC2, and then amplifier after IC2 in IC2 after driving the speakers are working. The power supply required for the motor high frequency head is provided by the triode 8050 and a high frequency transformer, which constitutes a boost circuit to provide a working voltage and a tuning voltage. It should be noted here that the power supply voltage cannot be too high, otherwise the high frequency head and IC1 do not match, and the signal blocking phenomenon is easy to generate. Practice has proved that the power supply voltage is preferably 4.6V, and 3.6V lithium battery can be powered by three-section battery or section 3.6V.
High frequency heads should be used to use high-increasing high frequency head TDQ-38, and AFC is empty. Second Improved / Mixed Selected Radio, high-frequency amplifier, mixed integrated circuit TA7358 (TA7335 improved), not only low, more excellent high-frequency amplifier mixing ability, high stable Sex, consistency, overall performance is not sub-NE602. And the LAP722 can exchange directly, and its pin function is shown. The second middle, demodulation is also used by the intermediate frequency integrated circuit TA7640 commonly used in the radio. Although it is the early product of Japan's Toshiba in the 1970s, but compared to ULN2204, TA8132, the intermediate frequency signal is strong, and noise is small. W trimpot selected multi-turn precision potentiometer 100kΩ the zapping easier and more stable. This machine is a digital voltmeter between the high frequency head VT and the ground to display the reception frequency, and it is not advisable to use the pointer voltmeter because the reading is not accurate, it is not easy to observe. High-frequency transformer B1, oscillating coil B2 uses a commercially available television medium TRF1445. Need not change B1, B2 remove the circle, B3, B4 in the periphery can be employed in radios. At the same time, pay attention to the same name of B3 when the installed is loaded, and the b3 can be changed.
This machine debug main adjustment B1, B2 enables 10.7 MHz intermediate frequency signal, then adjust B3, B4 makes the sound optimally.
If the receiving head is unmistable, it can be successful, the signal receives stable, the sensitivity is high, and only half a molt wire wire can be received to receive all of the FM radio stations and television signals.
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