Hold on pal before you misconstrue my post. Read the book or at least the excerpts written by my brothers at the FDNY (yes I am former NYC*EMS and one of the first Medics in the city). I worked the Medic unit that ran the 911 calls at the WTC and had I been working, would have been first in. The radios that were used that day had never been field tested. No-one heard the evacuation order because, among other things, the radio system and the XTS3000 radios sucked.
The story I read in the NIST report is that in the months leading up to 9/11, FDNY had stopped using the digital radios because a fire fighter's transmission was missed because of doubling of transmissions, which is far worse in digital than analog.
So on the day of 9/11, they were actually using old analog radios they had all along.
One can surmise they might not have been in tip top shape, being old radios, but on that morning, they were the "proven tech" that FDNY preferred.
There was a cross band repeater, UHF from the command center to a batallion chiefs vehicle where high power VHF is the fire ground channel.
Also a repeater of some sort in the building itself, wired to a handset in the lobby.
Because of the collapse, those in command were killed, and with them any after action report on those radios.
This paraphrased from NIST report slides, so please no flames....
The problem of guaranteeing coverage into critical structures often requires internal equipment like BDA or DAS, that rely on cabling which is vulnerable to physical destruction.
There really is no perfect solution for fire ground communications. I would be the first to opine that perhaps P25 digital isn't the best solution. The KISS principal, with simplex analog radios, are probably as good as you can do.
I don't think there is any shortage of blame to go around regarding 9/11. The radios certainly were taxed, as were fire fighter's ascending all those stairwells.
This disaster/terror/crime was in the making for decades, longer if you consider the geopolitical triggers.
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