Simple RF circuit design.?

I know this question has been asked many times before. but I could not find any suitable answer. I need a simple one-channel RF circuit that turns an LED on/off. I know electronics pretty well I did some stuff with my Parallel port on my computer to turn light bulbs on/off. I am trying to expand my knowledge of RF and wireless communications. Though I am sure it would teach me a lot I am NOT looking for an answer like "Purchase a kit" or "Buy a cheap doorbell on Ebay" I want to get my hands DIRTY!

Thank you very much for the help.

Update:

My mission is to accomplish a basic version of what's in a toy car/plane.

7 Answers

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  • John
    Lv 7
    7 years ago
    Best Answer

    Start by building an rf detector. Wrap some wire around a big ferrite rod - about 20-30 cm long - and connect it to the base and emitter of a transistor. Put a test meter in the collector circuit, and attach a 9V battery between meter and emitter. When the coil picks up RF the meter reading should change.

    Now you can improve this by adding a tunable capacitor across the coil.

    Work towards this circuit (link), but keep the capacitor in place across the coil.

    Dont use R3 C2 or C3 just connect the emitter directly to ground.

    Put an LED in the collector load. If you make R2 variable you can adjust the bias point so the LED is just barely on, and turns on when a signal is present.

    You can also try a jfet (2n3819) instead of the transistor.

    Electronics is a great hobby.

  • 3 years ago

    The link offers you a suitable circuit. Be conscious that this is not an effortless project, layout may be very crucial. You quite want at least an RF signal generator and an oscilloscope to get this working in any respect, and a spectrum analyzer to do a good job. Some kind of swept frequency test station would make existence quite a bit less difficult, corresponding to a scalar network analyzer. The test apparatus is on hand from Agilent. You can also get it used from Tucker electronocs, or on ebay. Edit: I located a much simpler receiver circuit that can be built with out making use of experiment apparatus, it's going to decide on up indicators out of your neighborhood airport. If which you could make it run, it can be modified for far off control use. It's simple enough that there's some hope of getting it to run simply using a crystal earpiece and a multimeter. A 'scope is not going to support you so much - it will load the RF side a lot as to stop it from working, and on the audio part it might just display white noise. The human ear does a greater job of picking the speech out of the noise.

  • Dave
    Lv 4
    7 years ago

    The link gives you a suitable circuit. Be aware that this is not an easy project, layout is very critical. You really need at least an RF signal generator and an oscilloscope to get this working at all, and a spectrum analyzer to do a good job. Some kind of swept frequency test station would make life a lot easier, such as a scalar network analyzer.

    The test equipment is available from Agilent.

    You can also get it used from Tucker electronocs, or on ebay.

    Edit: I found a much simpler receiver circuit that can be built without using test equipment, it will pick up signals from your local airport. If you can make it run, it can be modified for remote control use. It is simple enough that there is some hope of getting it to run just using a crystal earpiece and a multimeter. A 'scope will not help you much - it would load the RF side so much as to stop it from working, and on the audio side it would just display white noise. The human ear does a better job of picking the speech out of the noise.

  • 7 years ago

    High frequency RF transmitting and receiving technique is not as simple as to play with computer ports. Especial if you want to play with WiFi signal that running on microwave 2.4GHz range.To start learning it, I built simple AM transmitter and use AM band radio to capture its signal. Later on,jump to build short wave transmitter and then VHF,UHF transmitter. The higher carrier to deal with,the more difficulty I faced. Because one small piece of wire is considered a coil in UHF band.Besides ,power transistor running on UHF is very expensive,over $100 a piece once I purchased it 20 years ago. It has gold plated flat lead terminals. Microwave is much higher than UHF band, image how expensive parts it could be.

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  • Rick
    Lv 7
    7 years ago

    You can use some type of RF detector (use Google). If the output of the detector exceeds a certain threshold, then toggle a flip flop. The outputs of the flip flop can control a transistor to turn on the LED.

  • Anonymous
    7 years ago

    You should contact an engineering firm or the engineering division of some company.

  • Anonymous
    7 years ago
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