I'm not talking about a unique identifier that is programmed into a radio for it to transmit every key-up. I'm talking about signal characteristics that are individual to each transmitter that occur each and every time it is keyed up, regardless of any "signalling" feature. It's basically like splatter but on much faster timescale and narrower bandwidth. You won't hear it, it happens too fast. Even an unmodulated carrier will show this upon initial transmit. If you have a good enough oscilloscope, you'll be able to see those characteristics happen and the"fingerprint" doesn't change when you change frequencies. Change hardware in the RF path and you will change the fingerprint.Not *ALL* transmitters. It’s a feature. MDC, GeStar, DTMF, etc are all types of this signaling, but if I turn signaling off in the programming, no such “chirp” is transmitted.
I am WELL aware of MDC et al type radio identifiers. The chirp I'm referring to is NOT something that can be turned on and off and is absolutely NOT something programmed into the radio. You can clone two individual radios, turn off all signalling features and with a good enough oscilloscope, you'll be able to tell which radio was transmitting just by looking at the signal.
Every transmitter does this.