I would imagine something like that could work, if you had someone listening to the messages in that kind of format. But in this case, your receiver is in a satelite, seeking messages in one of two given formats. Making modifiocations as you discussed would be changing the format into something the receiver, both man and machine, was not looking for.

It seems to me as if you would be sending out FM radio waves to be received by an AM receiver. If you could get the signal right so it was received, it's probably only going to sound like static.