I am facing problems to reply to you in my last post. Your answer was:
I think there are a few things to consider here in this crystal switching application. It sounds like your shunt load conditions for the TCXO are up to 10pF-10kohm (in parallel) followed by a high impedance input IC. If my assumption is wrong let me know. In the high impedance IC termination case the ADG904 switch will have an attenuating effect on your sine-wave signal. Added in some large value series resistors to the switch should help e.g. 10k+.
My answer is:
I am not sure I understand why the switch will attenuate the sine-wave of the TCXO?
If I understand the switch correctly, it is a pair of CMOS transistors with very low capacitance to ground (3pF according to data sheet).
The RDSON should be very low, according application note http://www.analog.com/static/imported-files/application_notes/AN_952.pdf
It should be below 8 Ohm for signal levels below 1V.