1. INTRODUCTIONFM Ratio Receiver Project Report. The FM Band transmission has started veryrecently in India but its superior technique and quality has attracted the listeners.Unlike AM, the FM is a separate band and its frequency ranges from 88MHz to 108MHz. The FM Band can not be received by the conventional AM receivers. Each andevery AM receiver does not incorporate FM facility. The present project is a very lowcost project and it can be fitted to any radio receiver/audio system to receive FMtransmission. The circuit of this project is very simple and can be easily assembled.AntennaA theoretical study of radiation from a linear antenna (length l)Power radiated a (p/l)2This implies that for the same antenna length, the power radiated by short wavelengthor high frequency signal would be large. Hence the effective power radiated by longwavelength base band signal would be small for a good transmission, we need highpower hence, this also point out to be need of using high frequency transmission.ModulationIn amplitude modulated communication, propagation of radio waves from thetransmitting antenna to the receiving antenna takes place in the following twoimportant ways :1. Ground Wave Propagation2. Sky Wave Propagation.The transmitted radio waves are supported at their lower edge by the ground. Theradio waves have to be vertically polarized, so as to prevent the short circuiting of theelectric field component of the wave. The radio wave induces current in the ground,over which it passes. It attenuates to some extent due to partial energy absorption bythe ground.Types of modulations1. Amplitude Modulation :In the frequency range 500 kHz. to 30 MHz, amplitude modulation of the signal isemployed and accordingly this frequency range is termed as amplitude modulated
2. band (AM bond). The earth’s atmosphere is more or less transparent to theelectromagnetic waves in AM band. However, the ionosphere (the topmost layer ofthe atmosphere) does not allow the electromagnetic waves in AM band to penetrate itand they are reflected back. When the frequency of electromagnetic waves is above 40MHz, they are no longer reflected by the ionosphere but undergo refraction. Keepingthe above facts in view, the amplitude modulated signal in medium wave frequencyrange (up to 1500 kHz.) is transmitted by surface wave propagation or also calledground wave propagation. In the short wave frequency range (from a few MHz to 30MHz), the amplitude modulated signal is transmitted via reflection from theionosphere. It is called sky wave propagation.2. Frequency Modulation :For frequencies of electromagnetic waves above 40 MHz, frequency modulation ofthe signal is preferred. In the transmission of TV signals, the frequencies of theelectromagnetic waves waves employed ranges from 30 MHz to 1000 MHz. Thetransmission of electromagnetic waves in this frequency range can neither be made bysurface wave propagation nor by sky wave propagation. The surface wavepropagation is not possible for the reason that the ionosphere cannot reflect theelectromagnetic waves in this frequency range. Further, in the frequency range 30 cm.to 10 m. FM transmission are made from small antennas.AdvantagesNow-a-days there is a necessity of FM projects in the electronic market. Through thisproject different FM stations can be tuned but in India. Presently there is one FMchannel. As such the project is designed for one channel to avoid possible damage ofthe coil in tuning again and again. The FM transmission is stereo phonic. As such youcan connect it to any stereo deck and enjoy the stereo sound. Now a days two-in-oneand radios with FM band are available in the market. But without replacing your oldradio set you can connect this project to your old radio/two-in-one and enjoy the FMtransmission. It is quite economical too. Unlike AM receivers, the FM receiver isassembled through different stages.(i) FM Amplifier(ii) Mixer(iii) Oscillator(iv) AGC
3. (v) Discriminator (Detector)(vi) Audio Pre-Amplifier.Integrated circuitAll the functions are performed by the IC-5591 which is employed in the circuit. Theaudio signal available from the preamplifier is fed to audio output amplifier for furtheramplification. The RF of FM band transmission is fed to pin no. 2 of the IC TA5591through the aerial, which also works for FM amplifier, oscillator and mixer stage. Aceramic filter of 10.7 MHz. is connected to the local oscillator pin no. 4, 5 and 6 ofIC. A 9 volt DC supply is fed to pin no. 8 of the IC. Pin no. 10 of the IC isdiscriminator pin. The audio signal is available from pin no. 11 of the IC. Pin no. 18,19 and 20 of the IC are IF amplifier pins while pin no. 22 and 24 are local oscillatorpin. Two trimmers are connected to the circuit. The range of the frequency can bevaried by rotating the trimmers. A gang condenser equivalent to the value of thetrimmer can also be used in place of trimmer if available. This project can operate inthe range of 3V to 12 Volt DC supply. However the trimmers are to be adjusted to getbest reception.Apparatus requiredS.No. Part Qty.1. IC-5591 12. Ceramic Filter 10 MHz. 23. Resistance 56 E 14. Capacitor 470 PF 15. Capacitor 22 PF 46. Capacitor .022 37. 4.7 MFD/63 V. 28. One Pole two way switch 1
4. FM RADIO RECEIVER CIRCUITPosted by P. Marian in Radio | 44 commentsMore projects with: radio receiver Add to favoritesThis simple fm radio receiver circuit consists of a regenerative rf stage, TR1, followed by atwo of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audioamplification may not be necessary, in which case TR3 and its associated components canbe omitted and the free end of capacitor C5 connected to the collector of TR2.The critical part of the fm radio receiver is the first stage, TR1/VC1, where the wirings mustbe kept as short as possible. Coil L1 is formed by winding 8 turns of 1mm (20 swg)enamelled copper wire on a 6 mm diameter former, which is then removed. After that L1should be stretched carefully and evenly to a length of about 13mm.FM Radio Circuit DiagramTransistors List
5. TR1 = BF199TR2 = TR3 = TR4 = BC547Video presentation and photos of the working receiverbyAleksandarThe tunning capacitor VC1 is one of the two fm sections of a miniature fm transistor radiowith built-in trimmers (VC2). The “earthy” end (moving vanes and spindle) is connected tothe 22pF capacitor C1. The value of the rf choke L2 is not critical, anything from 1µH to10µH being suitable.The output is suitable for ordinary earphones connected in series to provide an impedanceof 64Ω.Tuning-in the fm radio receiverTo operate the receiver, potentiometer VR1 must first be advanced slowly (towards the endof the track connected to battery positive) until, at about the half-way point, a sudden slightincrease in background noise will be heard, indicating the onset of oscillation. It then should
6. be backed off, very slowly, until oscillation just stops; it then should be possible to tune insome stations.The correct frequency range of 87 MHz to 108 MHz can be obtained by adjusting VC2 at thehigh frequency (108 MHz) and slightly stretching or squeezing together the turns of coil L1at the end (87 MHz).
7. Build A One Transistor FM Radio updated designs! See below for: Click here for: My new, improved The new, improved One Transistor FM Radio Radio Shack Special FM Radio or Build Build this one transistorthis one transistor FM radio FM radio (my design) (Designed by Patrick Cambre)
8. Enlarge: [large] Enlarge: [medium] [large] See the new improved version on Patricks web siteMy DesignA printed circuit board for the original circuit is available through FAR Circuits. Askthem for "Andy MitzsOne transistor FM radio printed circuit board". The samecircuit board can be modified for the improved one transistor radio.IntroductionAM radio circuits and kits abound. Some work quite well. But, look around and youwill find virtually no FM radio kits. Certainly, there are no simple FM radio kits. Thesimple FM radio circuit got lost during the transition from vacuum tubes totransistors. In the late 1950s and early 1960s there were several construction articleson building a simple superregenerative FM radio. After exhaustive research into theearly articles and some key assistance from a modern day guru in regenerative circuitdesign, I have developed this simple radio kit. It is a remarkable circuit. It issensitive, selective, and has enough audio drive for an earphone. Read more abouttheory behind this radio on the low-tech FM page.
9. Constructionparts sourceExcept the the circuit board and battery, all parts are from Mouser Electronics. Acomplete parts list with stock numbers is listed below. The circuit board is availablethrough FAR Circuits. The variable capacitor is available through Electronix Express.layoutBecause this is a superregenerative design, component layout can be very important.The tuning capacitor, C3, has three leads. Only the outer two leads are used; themiddle lead of C3 is not connected. Arrange L1 fairly close to C3, but keep it awayfrom where your hand will be. If your hand is too close to L1 while you tune theradio, it will make tuning very difficult.winding L1L1 sets the frequency of the radio, acts as the antenna, and is the primary adjustmentfor super-regeneration. Although it has many important jobs, it is easy to construct.Get any cylindrical object that is just under 1/2 inch (13 mm) in diameter. I used athick pencil from my sons grade school class, but a magic marker or large drill bitwork just fine. #20 bare solid wire works the best, but any wire that holds its shapewill do. Wind 6 turns tightly, side-by-side, on the cylinder, then slip the wire off.Spread the windings apart from each other so the whole coil is just under an inch (2.5cm) long. Find the midpoint and solder a small wire for C2 there. Mount the ends ofthe wire on your circuit board keeping some clearance between the coil and the circuitboard.a tuning knob for C3C3 does not come with a knob and I have not found a source. A knob is important tokeep your hand away from the capacitor and coil when you tune in stations. Thesolution is to use a #4 nylon screw. Twist the nylon screw into the threads of the C3tuning handle. The #4 screw is the wrong thread pitch and will jam (bind) in thethreads. This is what you want to happen. Tighten the screw just enough so it staysput as you tune the capacitor. The resulting arrangement works quite well.AdjustmentIf the radio is wired correctly, there are three possible things you can hear when youturn it on: 1) a radio station, 2) a rushing noise, 3) a squeal, and 4) nothing. If you
10. got a radio station, you are in good shape. Use another FM radio to see where you areon the FM band. You can change the tuning range of C3 by squeezing L1 or changeC1. If you hear a rushing noise, you will probably be able to tune in a station. Try thetuning control and see what you get. If you hear a squeal or hear nothing, then thecircuit is oscillating too little or too much. Try spreading or compressing L1. Doublecheck your connections. If you dont make any progress, then you need to changeR4. Replace R4 with a 20K or larger potentiometer (up to 50K). A trimmerpotentiometer is best. Adjust R4 until you can reliably tune in stations. Once thecircuit is working, you can remove the potentiometer, measure its value, and replace itwith a fixed resistor. Some people might want to build the set from the start with atrimmer potentiometer in place (e.g., Mouser 569-72PM-25K).Substituting other componentsMany of the parts are fairly common and might already be in your junk box. Onlycertain component values are critical. The RF choke should be in the range of 20 to30 uh, although values from15 to 40 uh might work. The tuning capacitor value is notcritical, but if you use values below 50 pf you should reduce or remove C1. Thecircuit is designed for the high impedance type earphone. Normal earphones can beused, but the battery drain is much greater and the circuit must be changed. To usenormal earphones, change R3 to 180 ohms. Q1 can be replace with any high-frequency N-channel JFET transistor, but only the 2N4416, 2N4416A, and J310 havebeen tested. A MPF102 probably will work. C2 is not too critical; any value from 18to 27 pf will work. C7 is fairly critical. You can use a .005 or .0047 uf, but dontchange it much more than that.Improved design for more audio gainChris Iwata recommended some design changes that greatly improve the audio circuit,making it strong enough for regular earphones or even a small speaker. The sameFAR printed circuit board can be used with some modifications. The circuit board isimportant to make sure the tuning end of the radio works properly, so the audioamplifier changes can be squeezed onto the circuit board without fear of wreckingradio operation. Look closely at the new schematic for the new components and somechanged component values.Schematic diagram for the Original One Transistor FM RadioClick here for a PDF version of the schematic. You can also make this into a simpleCB radio receiver. See this PDF file.
11. Schematic diagram for the One Transistor FM Radio with Improved Audio GainClick here for a PDF version of the schematic.
12. One Transistor FM Radio with improved audio gain.Printed circuit boardThe printed circuit board for the original One Transistor FM Radio is availablethrough:
13. FAR CIRCUITSPrinted Circuit Boards18N640 Field CourtDundee, Illinois 60118(847) 836-9148 Voice/Faxemail: email@example.comSome wiring notes: Unless you have experience with super-regenerative radios, I highly recommend using the FAR Circuits printed circuit board. Connect the two sections of the variable capacitor (C3) in series to linearize the tuning somewhat. That is, use the connections on either end of C3 and dont use the middle lead. L2, the RF choke should not be near a ground. The same is true for L1. Capacitance to ground will disturb the feedback. The gain is just enough to drive an earphone. If you live too far away from radio stations, you might have trouble hearing one. There is no option here for an external antenna (that would require and extra transistor). You can drive a speaker if you add an external audio amplifier. If you want a little more audio gain, or you cannot locate a TL431CLP chip, you can use some other audio amplifier in the circuit where pins 1 and 2 of D1 normally connect. You can use an LM386 or a TDA7052 audio amplifier. Quasar DIY project kit #3027 is a complete TDA7052 audio amplifier kit and it works fine in this application.Parts list for original circuit (see schematic of the improved version for new part values)All parts except the RF tuning capacitor can be obtained fromMouser Electronicswww.firstname.lastname@example.orgThe RF tuning capacitor can be obtained fromElectronix Expresselectron@elexp.com
15. S1 Small SPST switch 10SP003 screws for mounting C3 (2screws for C3 48SS03 needed)nylon screw #4 nylon screw used for tuning C3 561-T0440037battery connector mini battery snap 12BC025
16. How to build a very simple FM/AM Receiver usingTDA7088 ?I was browsing the Philips website when I came to this IC : TDA7088 and I said wow , it was thesimplest AM/FM radio I ever saw. I looked on its price on a local electronic parts provider and it wasabout 5 RON (~1.7$) so it is worth building this radio as a hobby project.Features of the chip : Equipped with all stages of a mono receiver from antenna to audio output Mute circuit Search tuning with a single varicap diode Mechanical tuning with integrating AFC AM application supported Power supply polarity protection Power supply voltage down to 1.8 V.A simple circuit, taken from the application notes :
17. As we can see it doesn’t have an audio amplifier so you must build one for it! After another search Ifound an extremly simple and low cost (~1.2$) AA done with TDA7050 :After my exams I think will do it and put here the construction images .