This is an extremely complicated project, definitely not for a beginner. In laymans terms:- You need a filter that that sweeps across the whole frequency range, so you can pick out each signal in turn. This is done by means of a superhetrodyne ("superhet") receiver. The incoming signal is mixed with a local oscillator which produces lots of different output signals, one of which is Foscillator-Fsignal . This frequency is called the Intermediate frequency (IF) and is the one that is filtered out , amplified and detected and finally demodulated and is the output signal to the loudspeaker. So in a superhet receiver you tune the oscillator to get reception of different frequencies.
In your case to sweep 0-> 200 MHZ, you need an oscillator that sweeps from IF to 200+ IF MHZ. Which is difficult. Which leads another point, the IF must be above 200 MHZ, otherwise the receiver will try and receive its own IF frequency which will cause it to oscillate. The choice of IF is also governed by the fact that you must be able to filter the Foscillator-Fsignal out, which means that the IF must be at least 20% away from Fsignal, giving us the lowest IF of 250 MHZ. At this frequency filtering is not very effective, so you must then change the first IF back down to a lower frequency, say 10.7 MHZ, with a second mixer and fixed oscillator.
Do you really feel up to doing this?
Frank