I found some software that sends an 8 channel PPM signal out the computer's headphone jack.  Your supposed to connect it to their PPM pulse decoder board, which can control servos.  Or you can connect your radio Tx to the Pulse decoder board and control servos without a receiver.

But I want to control my Tx directly with my computer, and not use their pulse decoder board at all.  Will the transmitter (dx5e) take a PPM signal directly from a computer headphone jack?  Or is the voltage not right?  Or will the Tx, as the master, try to supply power to the slave, and fry the computer's sound card?  I know slave transmitters don't even need batteries, so the master transmitter must supply power through the trainer port.  Would this be bad for the computer?  Anyway, heres a link to the software if it helps:

http://www.gadgetparadise.com/901604/index.htm

I am trying to avoid having to buy something like a endurance RC PCTx, it seems unnecessary if its possible for a computer headphone jack to put out a usable PPM signal.  Thanks!