Long Range FM Transmitter 1

Long Range FM Transmitter 1

Long Range FM Transmitter 1

How to make a long range FM transmitter at low cost


The use of transmitters which have a more powerful output than the ‘flea-power’ are sometimes required when there are many obstacles in the path of the surveillance transmitter and monitoring station receiver, or the distance between them is too far so as to make a low powered device feasible. Whereas a typical microtransmitter will produce an RF power in the order of just a few milliwatts, i.e. a few thousandths of a watt, the VHF-FM transmitter described has a power output of between around a half and 2 watts, depending on the power source, which may be anywhere between 6 volts and 30 volts d.c. The battery or batteries should be of the alkaline high power type, since the current drain will be found to be relatively higher when compared to microtransmitter current drain. The power output of this device is somewhat proportional to the current drain and so therefore both may be decreased by altering the value of R6 to a higher resistance, or a variable resistor with a value of around 1k may be introduced in series with the existing R6, so as to give a variable power output. The variable resistor must not be a wirewound device because this would act as an inductor which will cause feedback problems.The audio input to the power oscillator, which incidentally is formed by TR2 and associated components, is derived from a piezoelectric microphone which drives the simple audio frequency amplifier TR1. The input of the audio amplifier is controlled by the gain pot R1, which selects the correct amount of voltage that is generated by the piezoelectric microphone, then connects this signal to the base of audio amplifier TR1 via C7. It may be found that there is insufficient housing space for a bulky piezoelectric microphone, so with a slight modification to the circuit, it is possible to employ an electret microphone insert as shown. Since the RF field that is generated by this transmitter is relatively large, the problem of RF feedback may very well be encountered. This may be overcome by placing the transmitter inside a metal enclosure, keeping all internal wiring as short as possible and the aerial wire.

Component listing for 1 watt transmitter

Resistors Semiconductors R1 = 27k TR1 = BC547 R2 = 330k TR2 = 2N2219 fitted with heatsink R3 = 5k6 MIC = piezoelectric microphone R4, 5 = 10k R6 = 100R

L = 6 turns 22 gauge enamelled wire wound on 3⁄16″ former


C1, 2, 3, 8 = 330 pF C4 = 2–10 pF trimmer C5 = 4p7 C6 = 1 nF

C7,C8 = 40uF/25V Electrolytic

Circuit diagram for Long range FM Transmitter

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October 5, 2009 - Posted by | project ideas, transmitter | , , , , ,


  1. it is simpal to make this long range fm transmiter1, it helpfull for the larner of the electronic and comunication students. it the model of the next genatation students.

    Comment by Harish v | October 17, 2009

  2. I like this Circuit very much. It worked well. Isn’t there other circuit diagrams powerful than this ? If plz send me. I am student of electronic engeenering. if possible send me basic principle of frequency transmissions.

    Comment by Govinda Sapkota | October 29, 2009

  3. sir
    how can we make a project to voice match i.e. if any one is speaking and our program will select only a perticuar voice of a person and reject other person’s voice .

    Comment by ankur | January 11, 2010

  4. Sir,i am in ec engg. Final year so what are the best project for me.

    Comment by Naimish | May 31, 2011

  5. Hey Dude. I am from pak..your blog is very special as i was finding the circuit diagram as like this .

    Comment by inayat | November 23, 2011

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