"Be not touched, she is a grease of hog with a face for the radio."
Emoción and toque conjugate a little differently. Then maybe I should have said "No emocionarse, ella es una cerdo grasiento con una cara para la radio." Oh well, the point is what sounds sexy on radio may not be suitable for TV and usually isn't if you've seen the air staff around here.
"I've noticed they'll often run a dead carrier for some time just before they actually start."
Most shortwave stations do. Older transmitters must be tuned up by hand after a band change and while new digital controlled units do it in seconds automatically there is the matter of electronically slewing the vertical takeoff angle of the antenna to put the strongest possible signal into the target area. Pulsing the transmitter and listening to the return signal (backscatter) between pulses accomplishes this. It's kinda like OTHR with a difference, a technique that's been around for decades, the carrier isn't really dead, you can see the pulses on an oscilloscope.
"The dead carrier came at the end of the transmission and her voice faded out more and more as the dead carrier got stronger and stronger."
Two possibilities here, one is broadcast stations and numbers stations are one and the same. Patching audio is a fairly complex affair and things often go wrong with ancient equipment, then there are some pretty lousy operating engineers. The other is just as likely, another station was tuning up on frequency and eventually swamped the first one. The beauty of "boat anchor" receivers is you can switch the AGC off, turn up the AF gain and use the RF gain as a volume control. That way you can dig the weaker signal out from under the stronger one.
"That's the beauty of using a human voice that was recorded onto digital media and played on the air using a computer that loops it endlessly."
Close but no cigar. Each word is recorded separately and the "text" compiled by computer. It's extremely simple for numbers, the groups are typed into text and read by the voice synthesizer, even the groups may be compiled by computer from the message to be sent. A more complex system is the use of phones (voice sounds) compiled into words like Perfect Paul and Paula on the NWS VHF broadcasts. If you have Windows you have Microsoft Sam, he can be a lot of fun to play with if you can find his hiding place.
"I wonder how many stations there are using her voice?"
Every one since sometime in the 60s when I discovered her.