Alternate Spectrum for Broadcasting: 2300~2495, 3200~3400, 4750~4995, 5005~5060 kHz
This is spectrum that has been recommended by other parties for additional expansion of the AM broadcast band.
This spectrum is also referred to as the "tropical bands". In Articles 5.16~5.20 of the ITU Radio Regulations (RR), the "Tropical Zone" is limited in Region 2 to the area between the Tropic of Cancer (23° 26' North Latitude) and the Tropic of Capricorn (23° 26' South Latitude). RR 5.21 allows an extension of the Tropical Zone as far north as 33° North Latitude subject to special agreements between the countries concenred in this region.
RR 23.3~23.10 describes this band as a type of broadcasting for internal national use within the Tropical Zone where it may be shown that because of the difficulty of high atmospheric noise level and propagation, it is not possible to provide economically a more satisfactory service by using low (LW), medium (AM/MW) or very high (VHF/FM) frequencies and is limited to powers less than 50 kW and can not interfere with non-broadcasting services outside of the Tropical Zone.
Who uses it?
Domestic incumbent users: 2300~2495 currently has 515 licences consisting mainly of Alaska Fixed Service, state offices of emergency services and the National Security Emergency Preparedness (NSEP) network used by the Regional Bell Operating Companies and independent telecommunications providers. 3200~3400 has 360 licenses in the Aviation Service and Alaska Fixed Service and NSEP. 4750~5060 has 74 licensees from the Alaska Fixed, NSEP, power and petroleum services. Federal use is unknown but is beleived to be as extensive and coordinated.
Foreign incumbent users: Unknown.
How do they use it?
ITU Region 2 allocation: In addition to broadcasting in the Tropical Zone, 2300~2495 is allocated to fixed and mobile services, 3200~3400 and 4750~4850 are allocated to the fixed and mobile (except aeronautical mobile) services, 4850~4995 is allocated to fixed and land mobile and 5005~5060 is allocated to the fixed service. Note that the spectrum from 4995~5005 is not allocated to broadcasting but instead is allocated to standard frequency and time signal for stations such as WWV and WWVH.
FCC allocations: 2300~2495 is allocated to fixed and mobile (except aeronautical mobile) services including Maritime (Part 80), Aviation (Part 87) and Private Land Mobile (Part 90) services. 3200~3400 is allocated to the fixed and mobile (except aeronautical mobile) services. 4750~4995 is allocated to the fixed and mobile (except aeronautical mobile between 4750~4850) and 5005~5060 is allocated to fixed stations. These two bands around 5 MHz are codified in Part 87 for Aviation and Part 90 for Private Land Mobile.
Federal Government allocations: 2300~2495 is allocated to fixed and mobile services. 3200~3400 is allocated to the fixed and mobile (except aeronautical mobile) services. 3200~3400 is allocated to the fixed and mobile (except aeronautical mobile) services. 4750~4995 is allocated to the fixed and mobile (except aeronautical mobile between 4750~4850) (no mobile operations between 4850~4995) and 5005~5060 is allocated to fixed stations.
Notes about US usage: In the 2300~2495 band, there are 11 spot frequencies that are intended for disaster communicatons and two frequencies designated for long distance communications in the private land mobile services.
Canada/Mexico allocations: Due to its location, Canada does not recognize the broadcasting allocation in these segments. Mexico does recognize the broadcasting allocation without any country specific footnotes.
REC analysis and opinion for use as alternate spectrum
The Tropical Bands exist for broadcasting in the middle latitudes because of the nature of the land in this region (think the Amazon and the Saharan Desert) and AM simply does not cut it and areas are too spread out to support FM. These broadcast allocations, which predate satellite, fill in that void. The rest of the world is using this spectrum for the reasons that is mentioned in the international Radio Regulations.
Consumer grade receivers that tune AM on the tropical bands are widely available. As these bands are used in Africa for broadcasting and the DRM Consortium is trying to promote DRM in that region, it would be more likely that consumer receievrs that turn DRM and are not software defined radios (SDR) will tune this spectrum.
The spectrum that is used by the state EOCs as well as the telco's NSEP network are critical communications tools which during a disaster or national security emergency where land based circuits may no longer be available will fill in some of the void. While this spectrum may not be deployed until it is needed, it still needs to be there if it does. (The NSEP dates back to the Cold War days but its usage as well as the state's usage is these days, more focused on widespread natural events than it is an attack on the homeland.)
This spectrum is too loaded and too critical to national security to consider any kind of alternative spectrum broadcasting.