Two Stage Fm Transmitter

This Kit is a masterful two dispose, 9V FM transmitter (Tx) after a occasion a dispose of up to 1 kilometer in the unconcealed. It uses an RF transistor in its output dispose. Distance of transmission is critically relative on the untrammelled Conditions (in a fabric or out on the unconcealed), form of aerial used (uncombined wire or dipole), untrammelled voltage (12V is emend than 6V) and if the tour is severe for climax performance. The kit is manufactured on a uncombined-sided printed tour consideration (PCB). It has a silk cloak plaster on top to aid fabric.On the plea tshort is a thicken misdeclare to aid in thickening. Protel Autotrax and Schematic were used to delineation the consideration. ASSEMBLY INSTRUCTIONS Components may be borrowed to the PCB in any classify. It is usually easier to add the meanest top components primeval then receipts to the taller components. The electret microphone should be inserted after a occasion the pin conjoined to the metal occurrence conjoined to the denying rebuke (that is, to the plea or cipher voltage cause of the tour. ) This is noticeefficacious after a occasion a '-' premonition at the MIC on the tour consideration printed plaster.To preserve immeasurableness all the resistors must be inserted established up on one end. Be prudent to get the transistors environing the redress way. Note three subject-matters: - the two 100n capacitors on the PCB possess 0. 2" and 0. 1" spacing. We possess put in components after a occasion the redress spacing for contentment of fabric. - we possess supplied prewound, pre-soldered enamel 6 mold & 8 mold wire twists. The legs should thicken promptly to the pads of the PCB. However, pay specific study to the thicken alliance in occurrence all the enamel has not been oustd. You may possess to thicken off or abrade off advance enamel from the ends of the two enamelled twists. a intercourse (or tap) is required from the average of the L1 tinned copper wire twist to the pad noticeefficacious TAP contiguous to the twist. Thicken a element of wire to the top of the average mold as shown on the plaster. Then thicken the other end to the pad straightway contiguous to the L1 twist. Disseminate out the twists of L1 environing 1 mm individually. Make abiding none of the loops of the twist are tender the loop contiguous to it. CIRCUIT DESCRIPTION The tour is basically a radio number (RF) oscillator that operates environing 100 MHz. Audio selected up and amplified by the electret microphone is fed into the audio amplifier dispose built environing the primeval transistor.Output from the collector is fed into the infamous of the relieve transistor wshort it modulates the vocal number of the tank tour (L1 twist and the red clipcap) by modifying the alliance capacitance of the transistor. Alliance capacitance is a exercise of the immanent discord applied to the infamous of the transistor T2. The tank tour is conjoined in a Hartley oscillator tour. The definite dispose built environing T3 amplifies the output RF premonitional. Let us contemcompound at the singular blocks of the tour advance closely: The electret microphone: an electret is a persistently abounding dielectric.It is made by heating a ceramic embodied, placing it in a magnetic opportunity and then allowing it to cautious occasion stagnant in the magnetic opportunity. It is the electrostatic equiponderant of a persistent magnet. In the electret microphone a slice of this embodied is used as segregate of the dielectric of a capacitor in which the diaphram of the microphone forms one compound. Sound presabiding propels one of its compounds. The propel of the compound veers the capacitance. The electret capacitor is conjoined to an FET amplifier. These microphones are mean, possess palliefficacious sensitivity, a large number response and a very low absorb.First annotation dispose: this is a rule self-biasing vile emitter amplifier. The 22n capacitor isolates the microphone from the infamous voltage of the transistor and singly allows alternating general premonitionals to ignoring. Oscillator dispose: whole transmitter deficiencys an oscillator to originate the RF consigner waves. The tank tour, the transistor and the feedback capacitor are the oscillator tour short. An input premonitional is not deficiencyed to maintain the bill. The feedback premonitional makes the infamous-emitter general of the transistor modify at the vocal number.This causes the emitter-collector general to modify at the identical number. This premonitional fed to the aerial and radiated as radio waves. The call 'tank' tour comes from the force of the LC tour to accumulation motive for bills. In a absolute LC tour (one after a occasion no hindrance) motive cannot be lost. (In an AC netperformance singly the resistive elements achieve scatter electrical motive. The absolutely reactive elements, the C and the L, right accumulation motive to be returned to the plan after. ) Note that the tank tour does not fluster right by having a DC immanent put despite it. Overbearing feedback must be granted. Clip Cap.The slots incause the clip cap are formd relish the chief of an arrow. The climax capacitance compute is when the arrow is in keen to the 12 o'clock lie. A 180o mold brings the clipcap compute to its minimum rated compute. After a occasion conjecture you achieve be efficacious to raise up a tefficacious of entirety capacitance compute (retain to add in the 10pF) to FM number. You can so veer the number by altering the immeasurableness among the twists of L1. Disseminate out the L1 twist large individually. The 10pF ceramic capacitor in correlative after a occasion the red clip cap achieve enefficacious you to strain the Tx in the 98 MHz to 105 MHz dispose of the wholesale FM knot.If you use a upper compute (for issue, 27pF) you achieve propel the number down towards the other end of the FM knot. This end generally has advance wholesale stations in it. Definite Annotation Stage: this RF dispose adds annotation to the RF premonitional. It deficiencys an RF transistor to Kit 32. TWO STAGE FM TRANSMITTER do this efficiently. We use a Zetex ZTX320. L2 (an RFC radio number suffocate) and the 10p capacitor in correlative after a occasion it are delineationed to imtwo harmonics from the tour. Output might from this dispose achieve be climax when it is straind to fluster at the identical number as the former dispose.This can be executed after a occasion the peaking tour granted and pictorial individually adown. A mean (10pF) coupling capacitor on the aerial is optional to minimise the pi of the aerial capacitance on the definite dispose LC tour. (We possess not used one in this tour. ) Dipole Antenna. Greater dispose from the transmitter can be obtained by replacing the half-wave antenna (the prolixity of wire environing 160cm hanker) after a occasion a dipole antenna. This is basically two wires immovable to two subject-matters in the tour which are wavering 180o out of sight after a occasion each other.Two such subject-matters are the antenna subject-matter and the aggravatebearing rebuke (the +9V trail. ) You can trial by biting the antanna wire in half, leaving half thickened into the antenna subject-matter and thickening the otherhalf to the +9V pad. Subject-matter the two wires in adverse directions. Untrammelled Voltage. Output might is so extensiond by using a upper untrammelled voltage. 9V is emend than 6V. The climax untrammelled voltage for this Kit is secure by the ZTX320. This is 15V but if you try this then the computes of some hindrances achieve possess to veer. You can trial after a occasion this.WHAT TO DO IF IT DOES NOT WORK Poor thickening is the most relishly deduce that the tour does not performance. Control all thicken alliances prudently underneathneath a cheerful trifling. Contiguous control that all components are in their redress lie on the PCB. Did you add the intercourse from the average of twist L1 to the pad noticeefficacious TAP? Control that the leads of the two twists L2 and L3 are not dry alliances. Use a multimeter to control this. Control that you possess not accidently formed a thicken intercourse among two pads which are contiguous to each other. Did you mold the switch 'on'.Check that you did not interveer the 4K7 after a occasion the 47K resistors. Is the ZTX320 environing the redress way and in the T3 lie. Possess you truly disseminate out the twists of L1? Some vulgar possess told us that each end of L1 should be determination aggravate and right environing tender the PCB. They so said that L3 should be disseminate individually a illiberal. See us at http://kitsrus. com COMPONENTS Resistors, 5%, 1/4W: 100R brown sombre brown 470R yellow violet brown 4K7 yellow violet red 22K red red odispose 39K odispose unspotted odispose 47K yellow violet odispose 1M brown sombre unpractised 1 1 1 1 1 2 1 Capacitors: Clip 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 Mean premonitional transistor BC547 2 6 mold tinned copper twist 1 6 mold enamelled twist 1 8 mold enamelled twist 1 9V battery chip 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 - twist L3 and the 47pF capacitor - deficiencys to be straind in classify to get climax might output. It has to be straind to companion the number of the oscillator dispose 10pF cap, variefficacious capacitor and tapped L1 twist.The output “peaks” as the tank tour is straind to companion the oscillator number. This peak can be measured on a multimeter. A peaking tour (shown adown) is merely an RF guide that uses diodes to load a capacitor. The voltage despite the capacitor is measured using a voltmeter set to a low voltage dispose (2 or 20V). The tour can be assembled after a occasionout the deficiency of a PCB. Merely thicken the components promptly to each other. The output (despite C2) should be conjoined promptly to the voltmeter input using banana plugs or a two of monograph clips determination to form.The input to the peaking tour is thickened to the antenna wire hole on the PCB, using a 5cm (2”) prolixity of wire. Switch the voltmeter to the 2V or 20V DC dispose. To strain the tank tour, merely propel the molds of the tank twist L3 advance individually or closer simultaneously until the balbutiation on the voltmeter is a climax. Note that the balbutiation achieve be inferior occasion you are tender the twist. You achieve approximately positively ascertain that the twist molds possess to be disseminate very far individually after a occasion the developed mold at each end of the twist approximately tender the PCB. Once the output is a climax, repropel the peaking tour and merge the antenna.If you veer the oscillator number by tender the clipcap then you achieve deficiency to relate the peaking proceeding in classify to get climax might output. Want Advance Range? You can get advance dispose as a employment off abutting stforce by: • imtwo R5 to 100R • imtwo R7 to 47R • incrcontentment C7 to 470pFor a reconsideration of Kit 32 and numerous other FM transmitter kits on todays communicate see: http://members. tripod. com/~transmitters/begin. htm To peruse the pregnant system aback the action of two dispose Fm Tx see: http://www. csn. ul. ie/~francis/fyp_report/