[gmcjetpilot]

http://ibis.experimentals.de/downloads/vorgsdiplexer.pdf

Found this jewel on the web. It is a bypass filter and instead of buying a $100 splitter you can make one for $20. Even if you don't make one its interesting to see how the high/low-pass filter works or looks like.

 

[SHIPCHIEF]

I love that kind of research. You won't save any money if your time is worth anything, but just knowing how it's done is worth something.
Someone also had plans for an antennae splitter so you could plug your handheld into the COMM ant, and cut out the Ship's Comm. From King, $75, home made $10. A good way to use your handheld as a powerful backup.