receivers in hand-held radios are subjected to signal levels that are likely to overload the receiver. Several radios may be transmitting within feet of one another on different channels. If overloading occurs, only very strong signals can be received while weaker signals disappear and are not received. The hand held radio receivers shown in the documentary appeared to work properly even though several other hand-held radios were transmitting only feet away. This is a hostile environment and suggests the hand-held equipment used by FDNY had good quality receivers, though in this case, the suggestion is incorrect. Second-hand observation is hardly the proper way to 'test' radio receivers or to distinguish 'good quality' from 'bad' and this is likely a source of continued misunderstanding; particularly when these same radios were operating at higher floors, in closer proximity to, and in direct line-of-sight of digital cellular repeaters. Those repeaters were likely operating at unlicensed power levels, which was a common practice of cellular providers at the time, and continues to this day. Footage reveals intelligible recovered audio coming out of the radios and shows radio users communicating with others. This may not have been true of the entire WTC complex but was true of radio users in the crowded lobby. Analysis of the 26 FDNY audio CDs showed the radios seemed to transmit into the radio systems okay. Radios calling dispatch got through. Calling units were intelligible. Users spoke with dispatchers. Dispatchers answered in ways that suggest they understood what was said. There were no noisy or truncated transmissions heard on any channel, (the equivalent of a dropped cellular call). This suggests the Fire Department's radio backbone is soundly designed and working properly. It is possible that system coverage problems are present; problems that could have been mitigated had the Command Post radio (with greater transmit power) been used. It is also likely that some transmissions did not reach any of the receivers in the system and therefore would not be a detectable problem when listening to the recordings. At the same time those recordings were made, the cellular system was operating at or near full-capacity, meaning every cellular repeater was transmitting. The dense RF interference environment created in NYC that day was essentially a 'perfect storm'; one in which a radio designed 25 years prior could not possibly contend with. In some scenes, captured documentary audio showed the channels were busy.