Uoi,
You should be using an RF switch to switch these types of signals (specifically the FM signal). This is due to bandwidth limitations on general purpose switches that would degrade your signal quality.
If your input signal is purely sinusoidal, which the FM and AM signals would be, the bandwidth/insertion loss rating is directly applicable. For example, a switch with a bandwidth rating of 10 MHz implies that the switch has an insertion loss of -3 dB at 10 MHz. If the input signal is a 10 MHz, 1V peak-to-peak sine wave, the output signal will be a 10 MHz, 0.7 V peak-to-peak sine wave. If you were to use a switch with a lower bandwidth, and place a high frequency signal across that switch you would end up with major signal loss through the switch.
I would take a look at RF Switches Above 40Mhz for all available RF switching modules above 40 MHz and select a switch with a bandwidth of at least 100 MHz. Additionally NI PXI Switch Product Selection Guide contain all of the switching modules that we sell and will detail specifications, topologies ect.
Frank,
National Instruments
Software Group Manager