For the ones not owning a scope.
I use another way doing it. I read about it at the forums at arduino.cc (
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1199165055) .
If you happen to own an arduino (
http://www.arduino.cc this little microcontroller costs like 30$ ("uno") in somw flavor (there is a huge amount of arduinos and clones) something like that and is attachable via USB directly), it's another way of doing it. Works for common PPM pulses at least.
Just put a few lines of codes into the microcontroller ( as seen in the example according to link, to read the PPM pulse in one pin. Code is downloadable via USB, no programmer needed for the micro controller.
Physically attach two pins to the object that needs to be ppm hacked, receiver, transmitter etc, gnd and the pin receiving the pulse. If pulse needs to be reversed, shifting positive/negative pulse. Then the pin values are replaced for example, HIGH could be replaced with low in the code, then this will shift the read pulse.
Then you can also read the values sent to the PC serial port via USB as well with IDE's serial monitor interface, let the internal onboard LED on the arduino blink as well, if pulse is there etc.
Simple but works pretty well. I have been playing around with it testing both negative and positive pulse on my 9X transmitter with er9x firmware, as it's configurable in the code.
I just thought this could be good to know for someone, if they have a need and missed this possibility. A scope is a scope, but this reads the ppm pulse values as well and could be used for other purposes as well, generating pulse also. Just thought it was worth mentioning as an alternative way...