Value chain · CLM-1072
In plain terms
In 1980 the radio astronomers expected to lose a twenty-degree circle of sky around the satellites and two of their bands, the spectrum managers found the beam's skirts spilling into the neighbouring broadcast band and its third harmonic into a government satellite band, and the military found the transmitter's hundred thousand tubes would together hiss over a five-hundred-kilometre radius.
The claim as recorded
The April 1980 EMC session's numbers. Radio astronomy (NRAO): the power signal at an observatory "not nearer than 100 km to a rectenna" is "35 dB above the overload threshold for a typical parametric amplifier, or 10 dB above the overload threshold for an FET amplifier"; "With 6 x 10^6 tubes in orbit, a tube lifetime of 220,000 hours results in 26 failures per hour"; a precluded zone around the satellites "estimated to vary from 20 deg for a single antenna to a few degrees for a VLBI system"; in the 2.69-2.70 and 4.99-5.00 GHz bands "sufficient filtering ... may not be achievable without significant impairment of sensitivity"; and the collector arrays' thermal emission at "approximately 360 K" from 60 satellites "probably results in a flux density level 3 to 10 dB lower than shown in Figure 1, i.e., very close to the CCIR 224-4 levels". NTIA: adjacent-channel noise in the 2500-2690 MHz broadcast-satellite band "as high as -124 dBc/4 kHz and -100 dBc/MHz"; "the 7350 MHz, 3d harmonic from SPS that falls within the 7300 MHz to 7450 MHz space-to-earth, government, satellite assignment"; unshielded integrated circuits at the rectenna centre 15.0 to 18.2 dB over their interference threshold, 1.3 to 4.5 dB at the edge and 5.4 to 8.7 dB under it at the exclusion fence 5.7 km out. DoD ECAC: in-band compatibility needs "frequency separation (df) >= 50 MHz and a distance separation of more than 25 km", harmonics "assuming the harmonics being 100 dB below the carrier" need "df > 20 MHz and a distance separation of more than 25 km", and the "103,000 klystrons" radiate noncoherent noise in a pattern "on the order of one degree" that "would cover a radius about the rectenna of approximately 500 km".
Evidence behind this: T3, three EMC abstracts' estimates for radio astronomy, spectrum management and military systems, with one rendered table of IC coupling margins.
Scope and limits
Estimates; the 26 failures per hour is the page's own arithmetic (6 x 10^6 / 220,000 = 27.3); Thompson's Figure 1 not rendered and its ordinate not read. Juroshek's "out of band radiation levels ... are currently unknown" and his figures are "representative of current technology".
What it assumes
Arndt and Leopold's 1978 klystron noise estimate for the transmitter-generated band; ECAC's 100 dB harmonic assumption is stated as an assumption.
Where it comes from
PDF p.440 / printed 419, normalised: "The typical level at an observatory not nearer than 100 km to a rectenna is estimated to be 0.01 Wm2, increasing by 5 dB if phase lock is lost" (exponent lost in the text layer; not rendered); the 35 dB and 10 dB sentence; "The collector array on each satellite subtends a maximum solid angle of 0.5 sq arcmin at the earth and operates at a temperature of approximately 360 K"; the 3 to 10 dB sentence. PDF p.441 / printed 420: the 26 failures sentence; "The mean distance between 60 rectennas within the U.S. will be about 350 km"; synthesis arrays less susceptible "by factors that range from 10 to 40 dB"; effects (1) to (3) as quoted; "The effects of intermodulation products and failure-related signals discussed above could be much more serious". PDF p.442 / printed 421: "The effects on ground-based optical astronomy are probably more severe than upon radio astronomy." PDF p.456 / printed 435: the -124 dBc/4 kHz and 7350 MHz sentences; "Catastrophic failures can be produced in integrated circuits when the microwave power levels coupled into inputs and power leads reach 1 to 100 watts ... interference, however, generally occurs with coupled power levels of the order of 10 milliwatts". PDF p.459 / printed 438, Table 3, render read: 7400 NAND, 4011 NAND, 5474 flip flop at Center of Rectenna +15.0, +18.2, +15.3 dB; Edge 5 km +1.3, +4.5, +1.6; Exclusion Fence 5.7 km -8.7, -5.4, -8.4; third sidelobe 17.0 km -18.6, -15.4, -18.3. PDF p.446 / printed 425: the df and distance sentences; "each of the 103,000 klystrons will generate noise. The noise from each klystron will be noncoherent with the others"; "The beam pattern will be much broader, on the order of one degree"; "This broad radiation pattern would cover a radius about the rectenna of approximately 500 km".
Basis: dB above receiver overload; degrees of sky; failures per hour; dBc per 4 kHz and per MHz; km and MHz separations
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-1072
CLM-1072, Energy Aperture, as of 1980-04.
Connected records
Other published records linked to this one. A list, not a judgement.
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