Value chain · CLM-1087
In plain terms
When the programme wrote down why it used 2.45 GHz, its reasons were consistent: each time it named the industrial band and how the beam passes through the atmosphere, and some documents added rain, good efficiency, antenna size or the outlook for the equipment.
The claim as recorded
The programme stated its reasons for 2.45 GHz four times between 1978 and 1981 and they are consistent: the DOE program plan, "The frequency of 2.45 GHz was selected because it (1) is in the USA industrial band and therefore should have minimal problems with respect to allocation and radio frequency interference, (2) results in near-optimum efficiency, and (3) avoids brown-outs in rain."; the reference system report, that molecular absorption and rain set "an upper limit on frequency selection of not much above 3 GHz", that 5.8 GHz is the alternative most considered, and that 2.45 GHz "offers many more" advantages - the middle of a 100 MHz ISM band, "lower attenuation when propagating through the atmosphere, and the projections for microwave equipment technologies are more promising"; TM-58232's system conclusion c, advantages "based on system trade-offs including (1) transmit antenna and rectenna sizing, (2) propagation effects through the atmosphere, (3) hardware technology projections, and (4) industrial, scientific, and medical (ISM) band utilization"; and TM-58236's reference system guideline 4, "Power transmission shall be by microwave at 2.45 gigahertz", the frequency being in an ISM band "that imposes no restriction on electromagnetic interference" and "subject to very slight atmospheric absorption", the guidelines being "a common point of departure" that "did not rule out the consideration of alternatives".
Evidence behind this: T3-four programme documents stating conclusions about the frequency, 1978-81; stated reasons, not the trade study behind them.
Scope and limits
STATED REASONS, NOT THE TRADE STUDY: the numbers behind "near-optimum efficiency" are CLM-1086's 1975 sweep and the 1977-81 sizing work (CLM-1089); these four pages state conclusions. "Avoids brown-outs in rain" is a 1978 plan's phrase and the 1981 assessments qualify it with hail (CLM-1089, CLM-1090). TM-58232's four trade-offs cite no page, and TM-58236's guideline is a guideline, adopted for definition work, not a finding. Three of the eight quoted spans are transcribed from renders because the text layers carry faults on the quoted words.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.17 / 8, NORM, the three-reason sentence. SRC-085 PDF p.122 / A-23, NORM: "molecular absorption and rain attenuation through the Earth's atmosphere sets an upper limit on frequency selection of not much above 3 GHz. Alternate frequencies have been considered in most of the microwave system studies to date, the most notable being 5.8 GHz."; RAW "the frequency of 2.45 GHz offers many more"; NORM "there is lower attenuation when propagating through the atmosphere, and the projections for microwave equipment technologies are more promising". The ISM sentence between them has "(" rendered as "{" in the text layer and is reported, not quoted. SRC-552 PDF p.68 / 52, render (extract/derived/SRC-552/render/p0068@2.0.png), TRANSCRIBED (text layer "has been[U+00B7] determined", "for.power", "includtng"): the conclusion c sentence. SRC-554 PDF p.30 / 20, render (p0030@2.0.png), TRANSCRIBED (text layer "al" for "at", "inte~ference", "absorptivn", "num~rous", "organization11"): guideline 4 and the guidelines sentence.
Basis: GHz; stated reasons
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1087
CLM-1087, Energy Aperture, as of 1978-1981.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-085
- CLM-0013The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per...CLM-0020The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at...CLM-0023In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed...CLM-0039The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and...CLM-0045The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0137In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam...CLM-0138The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency...More on the source page.
- Also from SRC-552
- CLM-1089The higher industrial band would have shrunk the receiving field to a fifth or a third of its size, at the price of a satellite that could...
- Also from SRC-554
- CLM-0911If the steering signal from the ground stops, the 1978 design's beam does not carry on pointing somewhere. It falls apart, and the power on...CLM-1017By 1981 the programme itself said the ionospheric limit it had designed to was probably too cautious, and worked out what relaxing it to...CLM-1018Three years of study left the efficiency chain exactly where 1978 put it, and Boeing's own version says out loud the solar constant the...CLM-1019The programme gave three reasons for choosing the klystron; the company that designed the satellite said the choice was more or less...CLM-1020By 1981 the programme was confident the beam could be pointed and formed, and named the network that carries the timing reference across...CLM-1022A loss you can make up by adding solar panels costs about 56 million dollars per percentage point; a loss at the ionospheric ceiling costs...CLM-1091The people running the programme said 2.45 GHz was sensible and also said, in the same breath, that nobody international had agreed to it...CLM-1478Almost everything that can go wrong with this design makes the beam fall apart and become harmless, which is the right way to fail. Two...