This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the beginner who wishes to get started in the fascinating world of FM broadcasting and wants a good basic circuit to experiment with.
4 Watt FM Transmitter – [Link]
This Phone FM transmitter connects in series to your telephone line and transmits the telephone conversation over the FM band when you pick up the telephone handset. Transmitted signal can be tuned by any FM receiver. The circuit includes an “On Air” LED indicator and also provides a switch which can be used to turn off the transmitter.
Phone FM Transmitter - [Link]
This is the basic fm trasmitter that I built. In theory, according to electronics, it shouldn’t work but works fine and is very sensitive. It can transmit the signal up to 45 yards (about 40 meters) . A sensitive FM radio can pick up the signal up to 100 yards (80 meters) but I can’t see any reason for it.
This kind of microphones are also called “spy microphones” but knowing that the battery is bigger than the actual circuit, I can’t see any application like that, anyway, this circuit should be used as educational application only.
Micro FM transmitter - [Link]
Here is a stereo FM Transmitter based on BH1415F wireless audio link IC. Phase Locked Loop controller use Microchip PIC16F628 and the the PLL frequency programming can be displayed with 8×2 and 16×2 LCD display.The frequency range can adjustable from 88-108 MHz.
Stereo FM Transmitter BH1415F – [Link]
This is a small and cheap FM receivers that you can get almost for free. It was based on the KA22429 which is equivalent to a TDA7021. It was easy to move it higher up into the VHF band covering up to more than 160 MHz. The details were published in Sprat in the Winter of 2004. [via]
Single chip VHF receiver - [Link]
The Hamtronics R139 WX FAX Receiver is a 5 channel crystal controlled receiver specifically intended for reception of the polar orbiting weather satellites that broadcast on the 137 MHz weather band. The receiver has a wideband IF that allows for reception of the wideband FM signal from the satellites. The received audio from the receiver is passed to a computer sound card where a program such as WxToImg is used to decode it to an image.
The R139 can scan the 5 channels and automatically stop on an active channel. This works well provided one has a strong signal. If the signal is weak or subject to fading the squelch will close and the scan will resume during the satellite pass which results in a truncated satellite image. For reception of the satellite pass horizon to horizon manual selection of the received channel and running with open squelch is needed. [via]
USB Computer Control for the Hamtronics R139 WX Satellite Receiver - [Link]
the author writes: Radio Shack Special…the name was given to it because all of the components may be purchased at your local or nearby hardware and Radio Shack store. Although Radio Shack does not carry a typical 6 lead AM/FM variable (tuning) capacitor for tuning in to all the FM stations, I have managed to come up with a simple little way of going from station to station by just stretching and sqeezing the DRAIN coil with some sort of non-metallic small stick; such as a tapered-wooden match-stick.
If you would prefer to use a variable (tuning) capacitor, you can always find these devices from any AM/FM tunable (not digital) radio or check to see if your local Wal-Mart carries a small blue portable AM/FM radio by ‘Lenoxx Sound’, which sells for around five dollars. From that radio, you can the salvage the variable (tuning) capacitor (with the plastic knob included), the headphones (in which I use for the Radio Shack Special) and the audio jack (also what I use for the project). A good buy for $5. The finished PCB in this project is adapted to either use a variable capacitor or not. [via]
One transistor super-regenerative FM receiver - [Link]
This is wireless FM transmitter project, when you speak into the transmitter and others hear you on any FM radio. The transmitter can be built in an afternoon with simple, affordable and widely available parts. Construction is fun and much can be learned although performance is modest; for example, your voice gets difficult to hear at distances greater than 25 feet. [via]
Wireless FM Transmitter - [Link]
This project supports both RDS (Europe) and RBDS (USA) Tuner FM band 88..108 MhZ (Europe and USA.) The schematic consists of two major subcircuits:
- The actual RDS/RBDS Decoder(TDA7330) with the PIC18F452 and the 4×20 LCD display
- The FM Stereo tuner with headphone amplifier.
You can choose between a 4×20 character LCD or a smaller graphical LCD to display data. A simple RS232 interface can also be used.
RDS/RBDS decoder - [Link]