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PLL FM Transmitter

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Hi Mayo,
I hope that you do not want to transmit on the FM broadcast band of 88 to 108 MHz because the VCO in the 4046 has a typical max. frequency of only 0.8 to 2.4MHz (page 7 on data sheet).
A broadcast band FM transmitter needs an 88 to 108MHz VCO which feeds a very high frequency digital divider. If you want to transmit on 100MHz then divide that down to 1MHz to feed one side of a phase comparator (you can use the 4046 phase comparator) and the reference frequency would be an accurate 1MHz crystal oscillator. Then you can frequency-modulate that oscillator a little with a varactor. The small amount of FM at the oscillator is multiplied by the divider (but also its frequency inaccuracy and drift).

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