Disclaimer, I am a ham radio operator, HF, VHF, UHF and also a satcom developer, engineer, so have some familiarity with two-way AM, FM audio communication. .. but not a pilot.
Using a handheld radio, tuned to 118 MHz to 136 MHz I am able to hear ATC ground communication and aircraft communication easily. Given that AM is used, occassionally several transmissions can be heard at the same time on the same frequency, and I am impressed by the professional comm skills of the ATC (my location near KDCA).
My question is multipart:
1) On board aircraft, what is the received quality of the audio transmission ? Is it always 5x9 ?
2) When multiple transmissions are received on the same frequency, how does ATC filter out who is talking, and fast, do they have an indication (sub-carrier identification ?) of who has keyed the mike - or is it upto the skill of the ATC operator.
3) When an ATC communication is sent, I hear the readback almost simultaneously from all the pilots who have had their call sign announced... followed by almost NO delay in the readback - is the audio quality onboard the cockpit that good (speaker -vs- headphone) that it is possible for the pilots who are listening to other chatter, other radios, intra cockpit communication to isolate and respond by keying the mic ? Also, I guess that having a good sharp memory to read back all the details given in a short burst transmission is a typical quality for a pilot right ?
To me, the fluency between TX/RX modes that I hear seems to have no time delay, and I am wondering how could it be so efficient.. I ask, since in HF and VHF radio QSO, it usually takes more than a second or two for each operator to get their radios on the air after being called by a net operator, and also allowing for the possiblity of someone else being on the frequency (listen before sending..)