Sean Michael Ragan writes:
This circuit is commonly credited to Japanese multimedia artist Tetsuo Kogawa. It takes audio input through a 1/4″ phono jack and, constructed as shown, without the optional antenna connections, will broadcast an FM radio signal about 30 feet.
Micro FM Transmitter – [Link]
Craig writes… [via]
I’ve made a half dozen battery-free crystal radios in about eight weeks. But I always wanted to try to stuff one inside of an Altoid tin for on-the-go. The short ground wire and long antenna wire that connect via an RCA plug, store neatly inside the tin. The 2000 ohm crystal earphone would fit in the tin if the long tube was chopped off. 200 turns of a 27 gauge wire on a 5/8” cylinder gets me tuning in the upper AM band. Perhaps I need to include a 3” copper ground spike to get a good ground in the field. Or would clipping onto a damp root be a better ground? Input?
Altoids Tin Radio – [Link]
The internet hosts lots and lots of online radiostreams, most of them with a certain theme, ranging from old time classics to Tibetian riverdancing. I must admit that I love to listen to them while I’m building stuff, as I can choose the music I like without listening to the same cd’s over and over again.
Build your own Wifi radio – [Link]
555 timer based AM radio receiver published on Tube Time is one of many entries for the currently running 555 contest. This project uses a 555 timer as AM demodulator plus amplifier to drive the speaker. The radio signal is tuned with an LC tank circuit. The 555 timer is configured as a PWM where a ramp signal is created with a capacitor and a potentiometer. The radio signal picked by the LC circuit is superimposed on the ramp signal which varies the duty cycle of the output PWM wave. The variation in the duty cycle corresponds to the audio signal in the radio waves.
555 Contest Entry: AM radio – [Link]
Traditionally, in a crystal detector radio tuned circuits, a mechanical type variable capacitor is used. For those of you who would like to eliminate this mechanical component, here is a modern version of the classic detector set. This radio, as shown on Figure 1, uses a varactor diode instead of the usual mechanical rotary device. [via]
Crystal Detector Radio Receiver Set – [Link]
This project shows how to build a simple AM radio transmitter based on 555 timer IC. The circuit parts are: the 555 timer IC, a NPN transistor three caps, three resistors and a potentiometer. The circuit is able to generate an amplitude modulation signal at 600Khz and you are able to receive it using a plain AM receiver. The range is about 30-40 feet. [via]
AM radio transmitter using 555 timer – [Link]
This Crystal Radio is highly selective as to separating stations and tunes in the A.M. band from 570 KHZ up to 1.7 MHZ and the short wave bands up to 2.5 MHZ. It is suggested that crystal earphones be used….. or (preferred) feed the audio output of this tuner into an audio amplifier. A good antenna of at least 50 feet is required along with a good earth ground connection.
High Selectivity Crystal Radio with Short Wave - [Link]
PicCon is a PIC microcontroller based radio controller designed for hidden transmitter hunting. When combined with a radio transmitter, it will produce tone sequences and Morse code messages at user-programmed times. It is completely field programmable via DTMF tones, utilizes EEPROM for all programmed options so they are remembered when power is removed, and is quite compact.
PicCon : Hidden Radio Transmitter Controller – [Link]
Greg Charvot has build this Homebrew Radio Transceiver for the 20 M SSB ham radio band from scratch. It is build using solid state components in low noise design philosophy. It uses a bi-directional signal chain rather than a separate transmitter and receiver. Check schematic and construction photos on the link below. [via]
Homebrew 20 M SSB Radio Transceiver – [Link]