High Power FM Wireless Microphone
This FM Wireless Microphone has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity.
This High Power FM Wireless Microphone has a better frequency stability, over 1 Km range and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little.
How to Make FM Transmitter
This tutorial is for making simplest FM transmitter using only one transistor. VC1 is a small, screw-adjustable, trimmer capacitor and its rating should be around 10-100pF. Set your FM receiver for a clear, blank station. Then, with a non-conductive tool, adjust the capacitor for the clearest reception, rotate it till the receiver receives a sound from the microphone of transmitter. Use the following formula for determining the frequency.
iPod FM Transmitter
Here are instructions for building your own ipod FM radio transmitter. It works quite easy, there is a power switch on the bottom to turn it on and tune your radio and transmitter to the right frequency. For the antenna you can use a copper wire of 70 cm. The range of this FM transmitter is about 100 to 150 meters (500 feet). With R5 you can adjust the input signal and with C6 you can tune your frequency. Transmitter is supplied by 9V battery.
Long Range FM Transmitter
The power output of many transmitter circuits are very low because no power amplifier stages are 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 signal power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2.
Long Range FM Transmitter
Presented here is a Long Range FM Transmitter. This circuit is a super-sensitive, mini-powered FM transmitter consisting of a RF (radio Frequency) oscillator section interfaced with a high sensitivity, wide pass-band audio amplifier and capacitance mike with a built-in FET (Field Effect Transistor) that modulates the base of the RF oscillator transistor. Transistor Q1 forms a relatively stable RF oscillator whose frequency and is determined by the value of coil L1 and turning capacitor C4.
Long Range FM Transmitter Circuit
This circuit is a circuit diagram fm transmitter. This circuit is somewhat different from the previous fm transmitter circuit. Transmitter circuit described here has the additional RF power amplifier stage, after the oscillator stage, to increase the power output of 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element yagi antenna, this transmitter can provide a good enough signal strength to a distance of about 2 kilometers.
Low Pass Filter For FM 88-108 MHz
Filter used for eliminate unwanted harmonic frequency at second and third. Notch filter, Band Pass Filter (BPF), and High Pass Filter (HPF) sometime combined in constructing LPF design.
Schematic below for FM Broadcast Lowpass Filter 88-108 MHz. It has been tested with a good result.
Note : Make the coils at 74 nH and trim them to adjust exact value.
Low Power FM Transmitter
This low power fm transmitter is designed to use an input from another sound source and transmits on the commercial FM band. This low power fm radio transmitter it is actually quite powerful.
The first stage is the oscillator, and is tuned with the variable capacitor. Select an unused frequency, and carefully adjust C3 until the background noise is removed.
The schematic you find here comes from another site on the internet, but because it's on so many sites, we don't know who actually designed it. However it's a nice one.
C1,C4 22pF cer.
C2,C3 51pF cer.
L1,L2,L3 #18 bus wire, 1/4"diameter, 3 turns
* Form the leads from the capacitors as shown in the little figure below. Then solder them from the pad to the outside ground area.
* Be sure that the turns from the coil are seperated by the same distance as the diameter of the wire
* Form the leads from the coils as shown in the little figure below. Then solder them in place.
* Place the filter in a metal box, with rf-connectors on both ends ( SO239(=PL259), BNC or N-connectors)
MC145170 PLL FM Transmitter
In order to simplify the transmitter design, we've used the new pll circuit from Motorola :the MC145170.
This PLL includes the prescaler and a serial standard bus called SPI.