Analyze My Homebrew Diplexer
What your trying to do here is build two filters, one high pass, and one low pass.
 Horizontal inductors shunted to ground with caps, create a low pass filter.
When the caps are horizontal and the inductors got to ground, you have a high
pass filter.

If you want to analyize this in detail you need to learn how to use a technique
called ABCD matricies.

http://en.wikipedia.org/wiki/ABCD_matrix_analysis

Each series or shunt impedance is entered into the 2x2 matrix, and then they are multiplied and you get a final relationship that describes the circuit.

For a simple circuit as you have here. there is no reason to go to the trouble,
as it is already well understood. The circuits are equavilent to a transmission line, below a critical frequency, and a low or high pass filter above. There are simple formulae that give the cutoff freq and the characteristic impedance
of the circuit.

These circuits need to be terminated in their characteristic impedance, or they will not work properly, and in that case you will get standing waves.

Your antenna has an impedance, so the filters need to be designed to work into that load impedance.