Tkil Posted August 18, 2006 Report Share Posted August 18, 2006 Hi,I've been studying about electronics for about 8 months. I have a question about tunning a radio. Tunning a radio is usually done by a variable capacitor or variable inductor. Why can't u tune using a variable resistor. They are much cheaper and smaller.Thanks a lot Quote Link to comment Share on other sites More sharing options...
indulis Posted August 18, 2006 Report Share Posted August 18, 2006 Think of this way... at what frequency will a RC or RL resonate?? That will lead you to your answer.... Quote Link to comment Share on other sites More sharing options...
ante Posted August 18, 2006 Report Share Posted August 18, 2006 Hi Tkil,You can use a variable resistor in a circuit with a GaAs-tuningdiode if you like. ;) Quote Link to comment Share on other sites More sharing options...
Guest nanop Posted August 22, 2006 Report Share Posted August 22, 2006 Hi Ante,What r tunning diodes. I never heard of them or how they work. ??? Do u also have pictures of it?Thanks-Nanop Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 22, 2006 Report Share Posted August 22, 2006 The capacitance of any diode changes when the reverse voltage across it changes. Varactor diodes look like ordinary diodes but are designed to have certain amount of capacitance and the capacitance changes quite a lot when the voltage is changed.Car radios, VCRs and TVs use varactor diodes for tuning. Quote Link to comment Share on other sites More sharing options...
Guest nanop Posted August 22, 2006 Report Share Posted August 22, 2006 Thanks Audioguru,Since the topic is tunning(radio), I recently found an old audio/radio system for TV. The Volume control knob said :o motorized volume. I took it apart, and I think I saw motor. I'm not sure how this thing works? ??? Quote Link to comment Share on other sites More sharing options...
walid Posted August 24, 2006 Report Share Posted August 24, 2006 HiThanks Audioguru,Since the topic is tunning(radio), I recently found an old audio/radio system for TV. The Volume control knob said :o motorized volume. I took it apart, and I think I saw motor. I'm not sure how this thing works? ???the motor acts simply as your handi have a remote controlled cd, when i press the + or - volume i can see the volume nob rotate it is connected by a motor rotate in two direction as the polarity applied on its terminalsFor the Varactor diodes, i can add to what my big friend guru said that its capacitance is inversely propotional to the applied voltage; whev v high , c is low so the tunned freq is highgood luck Quote Link to comment Share on other sites More sharing options...
Guest nanop Posted August 24, 2006 Report Share Posted August 24, 2006 Hi Walid,Thanks!Probaly that was why. When I bought the system, there wasn't a remote control, but there was a infared detector inside ???. When I saw the motor, and the words, no one would probaly know what it was used for unless they had a remote control :).Now I know one more part I can salvage from this system, and it would still work :)I have already salvaged some input jacks, and an infared detector, now a motor is on the way soon..... ;)Thanks :) Quote Link to comment Share on other sites More sharing options...
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