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FM Transmitter

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Here in Canada (and in the USA) FM radio station frequencies are at odd frequencies like 99.9MHz, 100.1MHz, 100.3MHz so 100.0MHz is not used. Even frequencies like 100.0MHz, 100.2MHz and 100.4MHz might be used in Europe.

If you use a quartz crystal oscillator and a harmonic of it at 100.0MHz then the accuracy depends on the spec's for the crystal. 

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  • 1 year later...

The frequency of FM broadcasting is high enough so that the signals go straight and far if there is nothing blocking them. But the curvature of the earth blocks distant reception.

Of course the range depends on the transmitting power and direction, and the sensitivity and direction of the receiver.

My FM transmitter circuit produces about 0.28W into a 75 ohms 80cm whip antenna. Its range is 2km across a large river valley to a very sensitive home stereo tuner or car radio, down the street to a cheap Sony Walkman radio, and across the street to a cheap clock radio. The tx and rx antennas must be parallel to get these ranges.

There is an FM radio station about 50km away from me with its antenna mounted on a small mountain. They get complaints of poor reception due to hills that block their signal.   

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