help- with varactor diode circuit
时间：04-09
整理：3721RD
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hello
i want to modify a tda 7000 fm receiver. it has varactor diode tuning. can anybody help me to modify it to operate in the 130 to 150mhz region? i mean what value of inductance is to be used to change it to the desired frequency with out changing the varactor diode given in the schematic. because i have ordered that diode..or at least please tell me the principle and formula for varactor tuning.i donot know how to select varacor diode. is there any way to measure the capacitance of unknown varactor diode.
i am enclosing the schematic.please help me.
i want to modify a tda 7000 fm receiver. it has varactor diode tuning. can anybody help me to modify it to operate in the 130 to 150mhz region? i mean what value of inductance is to be used to change it to the desired frequency with out changing the varactor diode given in the schematic. because i have ordered that diode..or at least please tell me the principle and formula for varactor tuning.i donot know how to select varacor diode. is there any way to measure the capacitance of unknown varactor diode.
i am enclosing the schematic.please help me.
MV2105 has capacitance between 10pF and 20pF for 2-10V bias.
For 130-150MHz range use a 110nH inductor (air coil inductor approximately 6 turns on 5mm diameter)
Max RF input frequency is 110 MHz for the TDA7000 (see page 2 in the data sheet). Low sensitivity is expected within 130-150 MHz. You may have to add a preamp.