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You need to post a schematic of what you have, but be aware that the free-running frequency (no PLL loop) will have to somehow be tuned to the center frequency.

 

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thanx Ron for the reply, and here's the schematic (see attachment). Actually, for the test, i'm feeding 1 Khz sine wave to the VCO input (pin 9). Before feeding that input, i could observe clean square wave output from pin 4 i.e. Vco out, just by using the capacitor...(I have not used any resistors). It was probably the center frequency of the VCO..i was however unable to record the value (the digital oscilloscope couldnt show any)... after feeding the sine wave, i'm unable to get anything..i tried changing capacitor values also... i think i'm having problems with the configuration itself.. could u help me?

Sheryl, maybe you haven't seen the TI CD4046 datasheet. It clearly says that the VCO requires one or two resistors.

 

i design it