what are Fm antenna specifications

As a part of project we constructed a fm receiver using cxa1619IC. we used a normal connecting wire as a antenna.I worked fine.But what was the effective length that must be needed and how can a wire receive the signals. What are the specifications needed while keeping an antenna for fm of 88 -108 mhz band.

Just work out the dimensions of a 1/2 wave dipole antenna for somewhere in the middle of the FM broadcast band.
The formula is really simple and readily available via google
For receive it will be very effective across the whole band
For added bandwidth across that 20MHz you can increase the diameter of the elements .... that will improve the tuning flatness.

Dave