![]() the next circuit (right) is only a base biased amplifier formed by 1M ohms resistor connected between the collector and base of the third transistor and the 4k7 resistor connected in the collector and 1.6 v vcc from the circuit. the 100 nano farad ceramic capacitor connected to the collector of the second transistor too is bypassing and avoiding the DC level and RF level, and only permits passing of most pure audio signals. as i saying the 3k9 resistor is biasing the tank circuit to make it stable and increase the gain. At the collector of the second transistor it's connected a 3K9 resistor (you can use a 2k8 to 3k9 resistor) testing try and error will make the best performance to your own circuit. One collector from the first transistor goes to 1.6 volts the new vcc of the circuit and the collector from the second transistor goes is biased by a 5k precision potentiometer to make sure hear the weak stations and adjusting the hearing of the circuit, in other words it's biasing the transistor to make sure it works correctly). the other terminal is connected to the base from the 2n2222 transistor connected in "cascade" or darlington mode to the second transistor to increase the current gain of the circuit. that is feeded by 2K2 resistor and 100 nano farad ceramic capacitor (left in the schematic). Once any frecuency between this range "catched" by LC will generate a voltage between the terminals of the tank circuit. The tank circuit it's calculated to work between 500-1500 KHz as said before. The Soul of the circuit it's the tank circuit formed by (inductor and capacitor in parallel) to make the "catching" RF waves circuit determined by the formula: 1/sqrt((L*C), where L is the value in Henrys of the inductor, and C it's the total capacitance from the trimmer a.k.a (variable capacitor). The circuit diagram shown in this step it's the complete and tested circuit. Once finished the winding and applied glue to the coil, it's mandatory to scratch the leads fo the coil to remove the aislant from the wire, and try measuring continuity to make sure there it is and the coil is formed correctly. You can use a little bit of glue, tape, or anything you want to maintain the windings in the place), see the images above to have an idea. (take it easy winding the ferrite core and do your best, nothing it's perfect). The internal diameter is about 0.8 centimeters of internal diameter, and about 58-60 windings of enamelled cooper wire of 30 AWG. Let's go, is MANDATORY to use a Ferrite Core from about 0.8 Internal diameter, it's not necessary to use a cylinder ferrite you can use a planar ferrite like me, if you don't wanna go crazy finding this core, you can recycle someone from an old FM/AM receiver. This is an IMPORTANT step cause this component is critical for the correct working at the desired frecuency range between (550-1500) KHz, the Modulated Amplitude Signal on earth. ![]() Breadboard Wire (it's recommendable to use 3 wire colors at least) You can control the RF GAIN, make son BIAS to the transistors to listen stronger and clear the Modulated Amplitude Radio Waves, of course this is not a simple Galena radio, but it has a better performance :)ģX 2N2222A TRANSISTORS OR ANY NPN BJT TO92 PIN COMPATIBLE like 2N3904ġX 104 (100 Nano Farad Ceramic Capacitor)ġx 103 (100 Nano Farad Ceramic Capacitor)ġx Knob for the trimmer or you can use a plastic point metal screw driverġx Female Headers (24 pin at least) for Connections & SolderingĢx AA Battery (Alcaline, Carbon, NiMH etc)ġx RF inductor (Hand Made) i explain how to make the inductor in the next steps from this instructableġx 5 pin of male headers (not showed) for easy plugging the audio jack to female headers. to listen many AM radio stations near and not very near from your home, and IT WORKS!!! I tested this circuit and make some improvements on it. And we don't use a all in one radio like the ZN414, MK484, TA7XXXX, one chip receivers in a TO-92 package, because in many places from the world is obsolete and hard to find :( you need to put your hands to work in this AMAZING AM Radio Receiver Circuit, yeah! wanna get that almost free RF Radio waves from the air and to be listened by you ears?ĭefinitely it is not a super regenerative or Heterodyne Receiver, not that kind of difficult stuff for many people who doesn't care about IF frecuency, AGC, RF filters, RF Cans, Decoupling Capacitors, Multiple Trimmers into a large capacitor and thing like that haha. Hello my friends at Instructables, I hope you are having a good time meanwhile you are reading this, if it is not well.
0 Comments
Leave a Reply. |