How to Operate Niftymitter V0.24

This instructable will tell you how to operate Niftymitter 0.24, a small open source FM transmitter. More information on the design can be found at www.openthing.org/products/niftymitter.

This transmitter is in development and has not yet been approved by any regulators. It is a low power transmitter and works over a very short range - please ensure that by using it you are not interfering with any other nearby transmitters.

Make sure your transmitter and radio receiver are at least 2m apart to avoid tuning in to a harmonic frequency. Switch on your radio and tune the radio in to the transmitter. This should be broadcasting on a frequency between 88 and 91 MHz FM, transmitting silence.

It is difficult to be accurate here as: a) the frequency can very depending on atmospheric conditions and b) the scale on your radio might be calibrated differently to the scale on my radio, so would give a different reading of what frequency it is receiving on.

If you are having difficulty tuning in, you may need to retune the transmitter, which is described in step 5.
 

Carefully turn up the volume on your audio source to a comfortable level. If you turn up too loud, the signal will sound distorted (it really doesn't need to to be very loud).

Slide out the circuit box.

Use a small 3mm slot headed screwdriver to adjust the 'trimcap'. It is best to use a screw driver with an insulated handle to minimise interference with the transmitting frequency, or ideally a trimtool such as this one from Rapid.
The trimcap is a small brass coloured component accessed by the hole marked 'tuning'. Clockwise for up, andticlockwise for down, it only requires very fine adjustment.
 

Slide out the battery tray. Unclip the battery from the PP3 clip, recycle/recharge and replace.