Value chain · CLM-1088
In plain terms
By 1980 the programme remembered its first study as having picked 2.45 GHz. The first study's report says it picked 3.3 GHz. The 2.45 GHz decision was made three years later.
The claim as recorded
The programme's own 1980 account of where 2.45 GHz came from does not match the 1974 document it names. The Boeing executive summary at the 1980 microwave workshop states that the first NASA study, by A. D. Little, Grumman, Raytheon and Spectrolab for Lewis, "completed in 1972, selected 2450 MHz as the transmission frequency and determined that apertures on the order of 1 km at the satellite and 10 km at the ground receiver would provide efficient energy transfer." That study's report, CR-2357, states "a frequency of 3.3 GHz was selected as the fundamental frequency for the main power beam of the SSPS and further RFI investigations were conducted on this basis." within a near-optimum range of 2 to 4 GHz, and designs amplitron magnetic circuits at 2.0, 2.45 and 3.3 GHz. On the held documents the 2.45 GHz selection is the 1975 Raytheon study's (CLM-1086), not the 1972 study's.
Evidence behind this: T3-a contractor's 1980 conference recollection set against the 1974 primary report it describes, both read at the page.
Scope and limits
A CONFERENCE SUMMARY'S RECOLLECTION AGAINST A REPORT, and the summary may be compressing a sequence (2.45 as a design point in 1972-74, selected in 1975) into one sentence. CR-2357's 2 to 4 GHz range does contain 2.45, and it says the choice within the band "should be made from the point of view of minimizing interference with other users" (reported; text layer "a[U+00B7] fundamental"), which is the criterion the 1975 study applied. So the disagreement is over which study made the selection, not over the reasoning.
What it assumes
That CR-2357 is the report of the study the 1980 summary describes. Its team, sponsor and dates match (ADL, Grumman, Raytheon, Spectrolab; NASA Lewis; contract work 1972-73, published 1974); no other candidate is held.
Where it comes from
PDF p.28 / 18, render (extract/derived/SRC-551/render/p0028@2.0.png); the sentence is TRANSCRIBED because the text layer renders "2450 MHz" as "24-50 \.\Hz". Same page, NORM: "The frequency selection of the original study was based on preliminary optimizations of energy transfer efficiency and" cost - the text layer has "ccst" so that word is outside the quoted span. SRC-472 PDF p.89 / 76, NORM, the 3.3 GHz sentence and "It is possible to select a near optimum range for the fundamental frequency from 2 to 4 GHz. Above this range, confidence in the design of devices, such as the Amplitron and associated filtering, decreases and the attenuation of the microwave beam by water-laden cloud increases, particularly for the low-probability instantaneous meteorological events."; PDF p.14 reported: "The choice of 3.3 GHz as the fundamental frequency for the SSPS was based on a set of assumptions for filter design"; PDF p.96 reported: magnetic circuits designed "at the main frequencies of interest, 2.0, 2.45, and 3.3 GHz"; PDF p.99 / printed 86 reported: "the SSPS Amplitron could operate at either 2.45 or 3.30 GHz"; PDF p.132: "Frequency: 3.3 GHz cw" among the study's SSPS specifics. Basis: GHz
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1088
CLM-1088, Energy Aperture, as of 1974 and 1980.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-551
- CLM-1090The programme's two printed tables of how much beam the weather eats do not agree. One has the ionosphere numbers the wrong way round, and...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-1408In the late 1970s, US studies sketched receiving stations raised on posts or legs so the ground beneath could still be farmed or built on...