Thursday, December 15, 2016

200-250 Milliwatts Long range FM Transmitter Circuit

Electronic Kit School. - There are many electronic circuit designed to give best result for FM transmitter with special range like for 87.5MHz to 108MHz for commercial radio transmitter and also 144MHz for community radio transmitter. The output power also many kinds depending the booster used. There are also FM transmitter circuit designed with many range frequency with low output power like the circuit of 200-250 Milliwatts Long range FM Transmitter shown in Figure 1. below.

In this moment we will show you one circuit of 200-250 Milliwatts Long range FM Transmitter Circuit that may useful for you who want to get this device. So, the main component in this circuit are transistor, capacitor, and inductor.

Circuit 

  1. Condenser MIC
  2. Resistors
  3. Capacitors
  4. Inductors
  5. Transistors
  6. Varicap Diode
Description

Circuit like in Figure 1 above show you about the 200-250 Milliwatts Long range FM Transmitter Circuit. From ElectronicsZone site describe that the power output of most of these circuits are very low because no power amplifier stages were incorporated.

The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres.

The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signals? power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2.

For better results, assemble the circuit on a good-quality glass epoxy board and house the transmitter inside an aluminium case. Shield the oscillator stage using an aluminium sheet.

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