Two Stage Fm Transmitter

This Kit is a masterful two measure, 9V FM transmitter (Tx) delay a file of up to 1 kilometer in the known. It uses an RF transistor in its output measure. Distance of transmission is critically hanging on the permitted Conditions (in a rendering or out on the known), archearchetype of aerial used (separate wire or dipole), permitted voltage (12V is reform than 6V) and if the tour is sharp for acme exploit. The kit is pretended on a separate-sided printed tour consultation (PCB). It has a silk cloak plaster on top to aid rendering.On the foot tclose is a strengthen misdeclare to acceleration in strengthening. Protel Autotrax and Schematic were used to plan the consultation. ASSEMBLY INSTRUCTIONS Components may be ascititious to the PCB in any classify. It is usually easier to add the decisive climax components primitive then produce to the taller components. The electret microphone should be inserted delay the pin conjoined to the metal contingency conjoined to the denying chide (that is, to the account or cipher voltage behalf of the tour. ) This is conspicuous delay a '-' token at the MIC on the tour consultation printed plaster.To catch extension all the resistors must be inserted decisiveing up on one end. Be cautious to get the transistors encircling the set-right way. Note three purposes: - the two 100n capacitors on the PCB feel 0. 2" and 0. 1" spacing. We feel put in components delay the set-right spacing for comfort of rendering. - we feel gifted prewound, pre-soldered enamel 6 reverse & 8 reverse wire implications. The legs should strengthen straightway to the pads of the PCB. However, pay extraordinary heed to the strengthen articulation in contingency all the enamel has not been migrated. You may feel to strengthen off or confricate off past enamel from the ends of the two enamelled implications. a intercourse (or tap) is required from the average of the L1 tinned copper wire implication to the pad conspicuous TAP proximate to the implication. Strengthen a division of wire to the top of the average reverse as shown on the plaster. Then strengthen the other end to the pad delayout-delay proximate to the L1 implication. Extend out the implications of L1 encircling 1 mm away. Make strong none of the loops of the implication are pathetic the loop proximate to it. CIRCUIT DESCRIPTION The tour is basically a radio quantity (RF) oscillator that operates encircling 100 MHz. Audio fine up and amplified by the electret microphone is fed into the audio amplifier meastrong built encircling the primitive transistor.Output from the collector is fed into the vile of the second transistor wclose it modulates the acoustic quantity of the tank tour (L1 implication and the red prescribecap) by modifying the union capacitance of the transistor. Union capacitance is a administration of the virtual distinction applied to the vile of the transistor T2. The tank tour is conjoined in a Hartley oscillator tour. The latest meastrong built encircling T3 amplifies the output RF tokenal. Let us face at the special blocks of the tour past closely: The electret microphone: an electret is a beamingly accused dielectric.It is made by heating a ceramic embodied, placing it in a magnetic scope and then allowing it to promising time quiet in the magnetic scope. It is the electrostatic equiponderant of a beaming magnet. In the electret microphone a mass of this embodied is used as dissect of the dielectric of a capacitor in which the diaphram of the microphone forms one dish. Sound presstrong agitates one of its dishs. The motion of the dish exchanges the capacitance. The electret capacitor is conjoined to an FET amplifier. These microphones are insignificant, feel excuseffectual sensitivity, a large quantity retort and a very low absorb.First expansion measure: this is a trutination self-biasing dishonoreffectual emitter amplifier. The 22n capacitor isolates the microphone from the vile voltage of the transistor and merely allows alternating present tokenals to ignoring. Oscillator measure: integral transmitter wants an oscillator to breed the RF conveyance waves. The tank tour, the transistor and the feedback capacitor are the oscillator tour close. An input tokenal is not wanted to support the bill. The feedback tokenal makes the vile-emitter present of the transistor modify at the acoustic quantity.This causes the emitter-collector present to modify at the corresponding quantity. This tokenal fed to the aerial and radiated as radio waves. The designate 'tank' tour comes from the ability of the LC tour to treasure essential-quality for bills. In a spotless LC tour (one delay no hindrance) essential-quality cannot be lost. (In an AC nettoil merely the resistive elements earn scatter electrical essential-quality. The spotlessly reactive elements, the C and the L, fitting treasure essential-quality to be returned to the classification posterior. ) Note that the tank tour does not ruffle fitting by having a DC virtual put resisting it. Real feedback must be granted. Prescribe Cap.The slots inbehalf the prescribe cap are fashiond affect the guide of an arrow. The acme capacitance appreciate is when the arrow is in keen to the 12 o'clock situation. A 180o reverse brings the prescribecap appreciate to its reserve rated appreciate. Delay empiricism you earn be commoditiesual to found up a teffectual of completion capacitance appreciate (mind to add in the 10pF) to FM quantity. You can so exexqualify the quantity by altering the extension among the implications of L1. Extend out the L1 implication large away. The 10pF ceramic capacitor in correlative delay the red prescribe cap earn eneffectual you to air the Tx in the 98 MHz to 105 MHz file of the retail FM bond.If you use a upper appreciate (for sample, 27pF) you earn agitate the quantity down towards the other end of the FM bond. This end generally has past retail stations in it. Latest Expansion Stage: this RF meastrong adds expansion to the RF tokenal. It wants an RF transistor to Kit 32. TWO STAGE FM TRANSMITTER do this efficiently. We use a Zetex ZTX320. L2 (an RFC radio quantity burke) and the 10p capacitor in correlative delay it are planed to subjugate harmonics from the tour. Output dominion from this meastrong earn be acme when it is aird to ruffle at the corresponding quantity as the anterior measure.This can be commoditiesed delay the peaking tour granted and descriptive partially adown. A insignificant (10pF) coupling capacitor on the aerial is optional to minimise the commodities of the aerial capacitance on the latest meastrong LC tour. (We feel not used one in this tour. ) Dipole Antenna. Greater file from the transmitter can be obtained by replacing the half-wave antenna (the extension of wire encircling 160cm desire) delay a dipole antenna. This is basically two wires sturdy to two purposes in the tour which are uncertain 180o out of exposure delay each other.Two such purposes are the antenna purpose and the real chide (the +9V trace. ) You can trial by sharp the antanna wire in half, leaving half strengthened into the antenna purpose and strengthening the otherhalf to the +9V pad. Purpose the two wires in counter directions. Permitted Voltage. Output dominion is so acceptiond by using a upper permitted voltage. 9V is reform than 6V. The acme permitted voltage for this Kit is determined by the ZTX320. This is 15V but if you try this then the appreciates of some hindrances earn feel to exchange. You can trial delay this.WHAT TO DO IF IT DOES NOT WORK Poor strengthening is the most affectly discuss that the tour does not toil. Obstruct all strengthen articulations cautiously inferior a amiable gentle. Proximate obstruct that all components are in their set-right situation on the PCB. Did you add the intercourse from the average of implication L1 to the pad conspicuous TAP? Obstruct that the leads of the two implications L2 and L3 are not dry articulations. Use a multimeter to obstruct this. Obstruct that you feel not accidently formed a strengthen intercourse among two pads which are proximate to each other. Did you reverse the switch 'on'.Check that you did not interexqualify the 4K7 delay the 47K resistors. Is the ZTX320 encircling the set-right way and in the T3 situation. Feel you truly extend out the implications of L1? Some tribe feel told us that each end of L1 should be disposition balance and fitting encircling pathetic the PCB. They so said that L3 should be extend away a dirty. See us at http://kitsrus. com COMPONENTS Resistors, 5%, 1/4W: 100R brown black brown 470R yellow violet brown 4K7 yellow violet red 22K red red ofile 39K ofile clear ofile 47K yellow violet ofile 1M brown black piercing 1 1 1 1 1 2 1 Capacitors: Prescribe cap 5-20pF, red 1 5. pF ceramic 1 10p ceramic 2 47pF ceramic 3 1nF ceramic 1 20nF or 22nF ceramic 2 100nF monoblock 2 RF transistor ZTX320 1 Insignificant tokenal transistor BC547 2 6 reverse tinned copper implication 1 6 reverse enamelled implication 1 8 reverse enamelled implication 1 9V battery snap 1 Electret microphone 1 PCB-mounted SPDT switch 1 Antenna wire 1. 6m k32 PCB 1 Peaking tour 1 packet of components Kit 32. TWO STAGE FM TRANSMITTER Peaking Circuit. Kit 32. The tank tour - implication L3 and the 47pF capacitor - wants to be aird in classify to get acme dominion output. It has to be aird to competition the quantity of the oscillator meastrong 10pF cap, varieffectual capacitor and tapped L1 implication.The output “peaks” as the tank tour is aird to competition the oscillator quantity. This peak can be measured on a multimeter. A peaking tour (shown adown) is merely an RF guide that uses diodes to accuse a capacitor. The voltage resisting the capacitor is measured using a voltmeter set to a low voltage file (2 or 20V). The tour can be assembled delayout the want of a PCB. Merely strengthen the components straightway to each other. The output (resisting C2) should be conjoined straightway to the voltmeter input using banana plugs or a couple of monograph clips disposition to fashion.The input to the peaking tour is strengthened to the antenna wire recess on the PCB, using a 5cm (2”) extension of wire. Switch the voltmeter to the 2V or 20V DC file. To air the tank tour, merely agitate the reverses of the tank implication L3 prefer away or closer contemporaneously until the balbutiation on the voltmeter is a acme. Note that the balbutiation earn be inferior time you are pathetic the implication. You earn approximately positively meet that the implication reverses feel to be extend very far away delay the decisive reverse at each end of the implication approximately pathetic the PCB. Once the output is a acme, reagitate the peaking tour and link the antenna.If you exexqualify the oscillator quantity by tender the prescribecap then you earn want to cite the peaking process in classify to get acme dominion output. Want Past Range? You can get past file as a exchange off across stationariness by: • subjugate R5 to 100R • subjugate R7 to 47R • incrcomfort C7 to 470pFor a re-examination of Kit 32 and multifarious other FM transmitter kits on todays trade see: http://members. tripod. com/~transmitters/begin. htm To interpret the ample hypothesis after the production of two meastrong Fm Tx see: http://www. csn. ul. ie/~francis/fyp_report/