At the same time, a steadily-increasing demand for better communications is faced within the territories of the United States itself. As distances increase, so do the advantages of superior communications - particularly in far-flung reaches of Alaska, Hawaii, and the Virgin Islands. Hawaii is distanced by some 2600 air miles from Los Angeles, while the Virgin Islands are distanced some mere (!) 1200 miles from Miami, and Juneau, Alaska a mere 900 miles from Seattle. Hawaii could benefit from Mainland Access by High Altitude Loiter Operations (an alternative meaning for the acronym, MAHALO).
The benefits of the skyhook approach may be obvious by comparisons to tests now being conducted in Hawaii to assess experimental HALO technologies using solar-powered transponder equipment on high-altitude ultralight aircraft loiter vehicles capable of operating at altitudes of 120,000 feet (an altitude at which practicable communications ranges may reach distances of 484 miles). The fact that these experiments are being conducted may illustrate the need for HALO/MAHALO technology, and further suggest its advantages as compared to satellite-based communications technologies.
Skyhook can be used in extending communications links beyond the "footprint" of a communications satellite, but may offer distinct advantages even where the alternative of satellite communications is already available. Radio communications conducted at UHF frequencies are governed by the universal square law of communications, and satellites at a height of 24,000 miles are 60 times farther away from a television receiver on the surface of the earth than a transmitter on a skyhook platform. Satellites have a larger footprint, of course, but they require 3600 times the power (or an expensive, dish-style satellite antenna). And satellite communications introduce an unwelcome "delay" effect to two-way communications.
The delay effect is something everybody knows from watching satellite coverage of distant events such as the war in Iraq, where newspeople conduct awkward conversations between interviewee and interviewer, who are separated (on earth) by a mere 10,000 miles, but conducting two-way communications over two or three links that make satellite "hops", each time covering some 24,000 miles, for a total communications path length of some 100,000 miles. Although radio waves travel at something close to 186,000 miles per second, it can take as much as half a second to travel each way, causing an awkward delay from question to answer. Skyhook-linked communications take a more direct path, and do not add nearly so much distance to the total communications path length. Skyhook networks offer improved immediacy of communications for live news links, because they eliminate much of the delay.
For communications with low-powered skyhooks over great distances, ground-based stations require specialized antennas similar to satellite dishes. For frequencies governed by line-of-sight transmission range limitations, signals can be "focused in" by these specialized antennas. Lower-power airborne transmitters have that disadvantage (which could actually be a non-jamming "security" advantage), but may be all that can be justified for point-to-point dedicated services, when co-hosted on a skyhook dedicated primarily to higher-powered broadcast services.
AM Broadcast Services
On the opposite end of the skyhook MAHALO applications spectrum, there is AM radio. In AM broadcast, transmission ranges are not necessarily limited to line-of-sight constraints, because the propagation of low-frequency electromagnetic waves is affected by a phenomenon called "bending", which permits propagation of radio signals beyond the horizon. The AM broadcast band is centered around 1 MegaHertz, where antenna expenses present a major problem, because larger antennas are required by the longer wavelengths. AM broadcast is tailored for mobile audiences (automobile listeners), by vertical polarization of its antenna towers, and antenna expenses are a non-linear function of antenna heights - which vary inversely with frequency.
In other words, the antennas are cheaper in the upper ranges of the broadcast band. Since AM covers frequencies from 550 to 1650 kHz, antenna lengths for the AM band vary by a wide ratio. Whereas an antenna for 1650 kHz station may be 250 feet, an antenna for 550 Khz is 3 times as tall. There is a lot of room at the low end of the band, where antennas must reach a height of 700 feet (or 70 stories). Antennas that call can be more than 10 times as expensive as their smaller cousins - which explains why the top end of the AM band has a lot of congestion (and why so many of the top-end stations use highly-directional antennas).
Though not restricted by line-of-sight limitations, AM is an expensive medium, because it requires more power. It's not uncommon to find AM stations broadcasting with 50,000 watts - which requires heavy-duty transmitters, which are expensive. It takes big money to support AM broadcast operations, because large amounts of electrical power are necessary to provide the necessary transmitter power. In a skyhook, this power provided by auxiliary power unit (APU). Although additional lift may be provided by the residual thrust of the APU, it may not be enough power for skyhook to simply "stay put" - and all the fuel the APU burns is a factor in determining skyhook's loiter times.
The issue of antenna expense may be addressed by suspending a long trailing-wire antenna from a skyhook, rather than a blimp, or an aerobically-stabilized, tethered balloon. One of skyhook's advantages compared to tethered balloons is the absence of a tether, which is a hazard to aviation in the vicinity of the balloon. If skyhook should be used as an AM broadcast platform, it should provide the benefit of some altitude advantage. Even with the expense of airborne power supplies, in some cases, skyhook could lower the power requirements (and energy costs) because the station's range of signal propagation may no longer be dependent upon the "bending" phenomenon
Another issue is the loiter times that are practically achievable. Skyhook AM operations may not be appropriate for routine broadcast operations, and may be limited to low-altitudes, and periodic intervals (daytime/drive-time), or temporary services, such as rescue efforts, natural disasters, or special events. Bandwidth constraints in the AM broadcast band may limit its usefulness to talk radio, but airborne, wide-bandwidth (multi-station), long-wire AM transmitters could reach wider markets, and accommodate special audiences (farmers, etc.)
VLF
Skyhook could be useful in the specialized function of NAVY VLF (Very Low Frequency) applications. Typically, these applications require "horizontal polarization", which is achieved by use of horizontally-oriented "long-wire" antennas, up to a mile in length, trailing from specially-equipped airplanes. Some portion of this function could be provided by radio-relay applications using two skyhooks, with a long-wire antenna stretched between them, or a group of skyhook vehicles, lofting an antenna device configured in a wide "ring".
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