Transmit FM audio on 434.65 Mhz. by substituting a Radiometrix NTX2 for a crystal oscillator in this circuit:
http://scitoys.com/scitoys/scitoys/radio/am_transmitter.html
Radiometrix: http://www.radiometrix.com/content/ntx2
NTX2 datasheet: http://www.radiometrix.com/files/additional/ntx2nrx2.pdf
On the NTX2, the connections are:
- 5V to the NTX2 VCC pin 4
- 5V to the NTX2 EN pin 5
- GND to the NTX2 GND pin 6
- Upper lead of audio transformer to the NTX2 TXD pin 7
A voltage divider input coupler will also work. See this post for a simple circuit: https://reactivemusic.net/?p=12263
notes
- Audio modulation level is very low. This circuit would benefit from a preamp. For example, as in this circuit by Amanda Ghassaei: http://www.instructables.com/id/Arduino-Audio-Input/
- Connect an antenna wire to NTX2 pin 2 (and 1 for RF ground)
- The circuit worked with 3.3 volts and would probably be fine with less.
- Used line out of an iPod touch for an audio source. Volume was up fairly high.
- You can also receive using AM mode using ‘edge’ detection
- In the US, you need a ham license to transmit on 434.65 Mhz.