Really? All 121.5 elt's transmit at between 75 and 100 milliwatts. All 406's transmit at 5 watts - 50 times the power and a hell of a lot more range. Most consider 100 milliwatts to be good for voice clarity at a 1/4 mile at the most. Aircraft at 30-40k feet would have to discern the (weak) tone from other background noise and clutter, and that has been determined to be difficult at best at that altitude. The satellites receivers were designed to pick out the (weak) tone and send it's location back to a ground station. There was over a 90% failure rate (false alarms) due primarily to not being able to discern an emergency tone from clutter/other noise - the main reason they stopped bothering to monitor it!You are way off on how radio transmitters work. All military aircraft are still required to monitor 121.5 and your theory on the 40K thing for airliners is false. If that were the case, satellites would never have been able to monitor 121.5. I don't disagree that 406mhz transmitters are the way to go, but please don't spread trash on a subject you have little knowledge about.
One of the problems with 121.5's was the satellite had to be very near overhead (and line of sight) to pick up a signal and then forward it to a ground station, hence coverage of only 60% of the earth at any one time and also why it could take up to 6 hours for a signal verification.
121.5 and 243.0 are still "guard" channels and are primarily monitored for VOICE emergency communications (usually transmitted at 5 watts or higher) - not elt's at 100 milliwatts or lower. Ask any SAR agency if they will deploy based on any single 121.5 signal tone. Also ask anyone the effective range (discerned identification of signal or voice) of a 100 milliwatt transmission. Go ahead ask and then get back to us without the snide commentary please.