how about the steel-framed apartments and condos in Manhattan that inhibit MW? Most workers in America work in steel-framed skyscrapers and the second most common is a steel-framed low-rise. What will these people do when there is a disaster during working hours?
They will do just what they did in previous situations like 9-11, and the three big power blackouts, they will walk out of the buildings and onto the street, and those with AM radios, particularly those tuned to the all news stations, will get the information they need about what is going on. In all these situations, there were only a few FM stations coming in from transmitters in New Jersey, while the important AMs stayed on the air. Some NY FMs now have backup transmitters a few blocks away from the Empire State Building on a building in Times Square with backup generators, but, obviously, the building isn't as tall and the signals don't go as far.
I don't know about the multipath conditions in Manhattan offices, but Missouri City towers penetrate Downtown Houston skyscrapers very well and the sprawl (and wood-framed housing stock) eliminates almost all multipath (and signal absorption) in the suburbs.
Depending on the station, and the building, many NYC FMs are not receivable in the building interior. I used to work across the street from the World Trade Center with a full view all the way up to the broadcast antenna on the North Tower. Even with very high quality FM receivers you could only get a signal if you left the radio near the window. That's the situation all the time, not just in emergencies. The 50-kw AM signals were not much different.
How many New Yorkers live within the 60 dBu signal of a FM? All 8 million in all 5 boroughs (plus some Jerseyites along the Hudson)!
There are 15-million people in the "official" NY Arbitron radio market, and the FM signals go past the market boundaries in all directions except on Eastern Long Island where some AM signals used to show up in the local embedded market ratings, but the NYC FMs did not, because FM signals don't go that far.
However, the big NYC AMs show up in in many adjacent markets during the day, including in Connecticut, New Jersey, and Pennsylvania, where several have shown up in the major market Philadelphia ratings for decades. Some of the AM stations can also be heard along the coast from Massachusetts to Delaware and beyond during the daytime. At night, the big NYC AMs cover 18-states and several Canadian provinces. The FM stations don't do any of that, and in a large scale national emergency would leave those extra listeners out of touch.
Actually migration data shows that the Sunbelt (Class C country) is still growing. The South is the most populated region.
Yes, but until everybody moves to Class-C country, we have to plan for Class-B populations.
I think FM radios are sufficient and sensible in the cell-phone example.
If it only costs pennies a cell phone, why not have both AM and FM, just in case? AM just has those extra benefits that many people may need, depending on what happens. So why exclude it?
In the case of a solar flare EMP, those old simple AM transmitters might have the best chance of survival. The towers are well grounded, and some co-located block house studios were built inside Faraday cages to save the audio engineers from constantly fighting RF problems, from their own transmitters, in their studio audio equipment. All you need is a handful of 50-kw stations to cover the country should more complicated modern equipment become instant toast, especially those devices connected to the grid or other wired networks.
My personal view is that AM is a technology that is rapidly becoming outdated, and where it stands depends on the market, and the signal power. Let's not forget that this thread is about testing a digital MW replacement for Ancient Modulation. For emergency communications full power digital would have all the strengths of AM, remote transmitters with backup generators and the potential of lots of stored fuel, greater signal coverage in many markets, and skywave coverage of much larger areas at night.
Right now, when it comes to new generations of cell phones it doesn't have to be AM or FM, when for pennies it can be both. If MW goes full power digital, future phone generations can be made to receive those signals. The idea is to have as many options as you can, just in case. Because you won't know, until it's too late, which options will still work.
