Value chain · CLM-0990
In plain terms
The extra twenty decibels of noise suppression for a fleet assumes a hundred satellites. The government's reference plan was sixty, which needs about eighteen decibels; the hundred was a convenient round figure that the workshop papers used and said so.
The claim as recorded
The "100 satellites add 20 dB" scaling that SRC-451 states in 1975 (CLM-0961) is restated in 1979 by Dickinson against CCIR 224-4's 2.7 GHz continuum limit - "Within a 30-MHz RA band at 2.7 GHz, -255 dB(w/m2 Hz)... For the case of 100 satellites, an additional 20 dB is required" - and the 100 is a round working number: the reference system's count is 60, and Hvatum's paper in the same volume says "approximately 100 SPS sets (60 and 120 sets have been mentioned)". For 60 satellites the incoherent addition is 17.8 dB.
Evidence behind this: T3-proceedings; the 20 dB is a stated scaling, the satellite count a stated range.
Scope and limits
DICKINSON'S -255 IS THE 1420 MHz LINE OF TABLE I APPLIED AT 2.7 GHz, WHERE THE TABLE ITSELF GIVES -247 (CLM-0988); the 8 dB difference is on the page and not explained there. The 15 mW and the 156 and 206 dB reductions are Dickinson's own chain, not recomputed here.
What it assumes
Incoherent addition across satellites, as in CLM-0961.
Where it comes from
PDF p.131, raw: "Within a 30-MHz RA band at 2.7 GHz, -255 dB(w/m2 Hz) implies total noise emission of 15 mW by an isotropic radiator at a distance of 35800 km... If a sub-array gain of 50 dB is assumed, numbers are decreased by 10^5... For the case of 100 satellites, an additional 20 dB is required. Depending on transmitter amplifier and antenna design, this level of performance is at least conceivable... Each satellite has 10^5 x 70-KW klystrons." PDF p.133, normalised: "If one assumes that a complete SPS consists of approximately 100 SPS sets (60 and 120 sets have been mentioned), the average distance between two adjacent rectennas will be about 300 km." Sixty satellites at PDF pp.7, 36, 46, 159 and 163. 10 log 60 = 17.8 dB.
Basis: dB of additional suppression; number of satellites
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0990
CLM-0990, Energy Aperture, as of 1979.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-516
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