Keywords: hands-on homemade portable 45 ~ 470MHz FM receiver
Hand homemade portable 45 ~ 470MHz FM receiver
The receiver has high receiving sensitivity, simple line, easy to install and debug, power supply, stable working, small power consumption, small size, easy to carry. The electrical material diagram is shown in Figure 1. Working Principle: A weak frequency modulated signal received by the high frequency header and mixed, and the 31.5 MHz sound intermediate frequency signal generated after mixing is output from the IF end. IC1 collects into blocks for the FM (due to the high frequency head has good tuning reception performance, and the TDA7010T is a dedicated frequency frequency receiving IC, and the receiving sensitivity is 3μV, which ensures that the whole machine has high receiving sensitivity), the intermediate frequency signal input IC1 { 11} The foot is frequently amplified by IC1. After the frequency modulation is output, the audio signal is output by the {2} foot, and IC2 is used to amplify the audio signal power. T1, T2 and LED1, etc., constitute a tuning indication circuit. T3, DW1, T4, and related components form a 6V voltage regulator circuit, providing a stable operating voltage for high frequency head and IC1. T5, T6, B and related components constitute a boost inverter circuit, detect the output voltage through T6, D3, DW3 to control the oscillation intensity of T5 to achieve regulatic energy saving. The inverter circuit outputs a 33V tuning voltage for high frequency head tuning settings. RT is a temperature compensation resistor, which is used to compensate for the initial initial charging of the boot caused the 33V tuning voltage to be slightly insufficient (very slightly, and it is not measured by the multimeter). Figure 2 is a pre-selection stage circuit and is used in conjunction with K1. Component selection and production: High frequency heads can be used with TDQ-3 type 470MHz full increase of high frequency heads, and the AFC foot leaves, R1, R2, C1 use micro or patch elements, which can be directly soldered in the high frequency head shield. The tuning potentiometer W2 uses 100KΩ multi-circle potentiometers to make tuning settings more convenient and more stable. IC1 peripheral circuit should be installed with a patch component, and the 0.4mm enameled wire is formed around 23 turns on the beads of ∮3mm. The boost inverter B is magnetically core with a small magnetic ring (can be removed from the old electronic ballast), using a transparent adhesive package to be insulated, with a ∮ 0.25mm enamel wire to wind, data is shown in Figure 1 The value marked. The role of L3 is to provide a bias voltage that is slightly high (about 0.8V) than the power supply voltage to ensure that the battery voltage is lowered to 6.2V, there is still a 6V stable voltage output. T4 is used as a constant current pipe, and DW1 provides a stable bias current. Since the power supply circuit has adopted corresponding measures, the 6V output voltage and the 33V tuning voltage are very stable, and the high band of high frequency head and medium placement frequency circuit are guaranteed. The power supply is selected from the 6-segment nickel-hydrogen charge battery or two lithium rechargeable batteries, and CZ2 is an external power jack. The speaker is selected from the magneticity, and the whole machine can be installed in a plastic box of 14.5 cm × 8 cm × 2.2cm. Debug: The only debugging of this receiver is the reception frequency of IC1. In order to ensure its tuning of 31.5 MHz, it can be commissioned with a normal receiving TV: 用 to connect the television high frequency head IF end with the wire (ie {11} foot), and connect the ground; adjust L Make it to receive a sound signal. The working current of the pressure inverter circuit is about 12 mA; the thermal quiescent current should be less than 45mA; the power supply voltage is changed between 6.2 to 9V, the whole machine current is basically unchanged. Use effect: This receiver has been used and inspected for more than half a year, and the effect is very satisfactory. High receiving sensitivity is high (receiving local FM broadcasts and television signals can be only a few centimeters long), the work is stable and reliable, the power consumption is low, the small is small, and people are not released. Since the high frequency head has adopted a low voltage power supply, its operating current is greatly reduced. Therefore, the whole machine operating current is small, which is beneficial to use the battery. The shortcomings of this receiver is that the initial need for starting from about 3 seconds can enter a stable operating state.
Be
+++++++++++++++++ pulls scroll bars View full circuit ++++++++++++++
Our other product:
