Value chain · CLM-0960
In plain terms
The 1975 study found the satellite's harmonics - the multiples of its transmit frequency - would trouble radio astronomy at the second and third harmonic, would trouble ordinary radio only at the klystron's second harmonic unless a filter was added, and would be clear at the fourth. A later reading of a redrawn chart says all three harmonics exceed everything. The original does not say that.
The claim as recorded
The same study's harmonic analysis concludes that the klystron converters' second harmonic would interfere with commercial services without a further -22 dB filter, that the second and third harmonics of all converters would interfere with radio astronomy but not with commercial services, and - verbatim - that "The fourth harmonic of all three tubes is below the level of radio astronomy (Class A)." It recommends that "Radio astronomy and similar sensitive receiving systems will need notch filters to protect against MPTS harmonics." SRC-439 reads SRC-111's redraw of this as "the 2nd, 3rd, and 4th harmonics will all exceed various CCIR recommendations, and ITU regulations for both Klystron and Amplitron systems". The primary says the fourth clears radio astronomy and only the klystrons' second touches commercial.
Evidence behind this: T3-primary-report, the primary behind SRC-111's Figure C.
Scope and limits
COMPUTED, NOT MEASURED - a power budget of total power plus effective harmonic gain minus path loss minus three filter terms, with harmonic gains of 18.7 to 34.4 dB from an effective-area argument using a K factor of 0.15, 0.04 and 0.01 that the report itself calls an estimate. Where the broadening to "all three exceed" happened is settled in two steps and only the second is an overstatement: SRC-111's Figure C keeps the data faithful to the dB but substitutes its own, stricter and later limit lines, cited on the figure - CCIR 1974 Report 387-2 for line-of-sight links at about -140 to -150, against the -116 this study used - so on SRC-111's own figure the klystron third harmonic exceeds too, and its text says exactly that: "in some cases (e.g., 3rd harmonic) violate ITU radio regulations". SRC-111 does not say the fourth exceeds; on its own figure the amplitron fourth sits 20 dB below the radio-astronomy line. The broadening to the fourth is SRC-439's reading of the redraw, not the redraw.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
Computed on PDF p.60: amplitron with filter at 2f0, 3f0, 4f0 of -144, -147, -185 dBW/m2; 5 kW klystron -104, -141, -174; 48 kW klystron -95, -132, -165. Limits: worst-case commercial IRR about -116; radio astronomy isotropic IRR rising from about -177 at 3 GHz to -163 at 10 GHz, taken from "REP 224-2, page 437" - SRC-111 cites 224-3 Annex 1, the next edition, which is not an error. The fourth-harmonic sentence matches at the normalised level on PDF p.61; the notch-filter sentence on p.63. The -22 dB filter and the per-service conclusions are transcribed from letterspaced pages. The two secondaries read directly: SRC-111 PDF p.20, "Figure C shows estimated levels of harmonic power (from Reference R-31) with recommended interference limits. Because of uncertainties in antenna gains and appropriate bandwidths comparison of the two is not entirely straightforward" (normalised; "1 eve1 s" for "levels"), and PDF p.22, "SPS harmonic radiation would exceed established recommendations and in some cases (3.g., 3rd harmonic) violate ITU radio regulations" ("3.g." for "e.g." in the text layer). SRC-439 PDF p.11, normalised: "the report shows that the znd, 3rd, and 4th harmonics will all exceed various CCIR recommendations, and ITU regulations for both Klystron and Amplitron systems" ("znd" for "2nd", "a l l" letterspaced), followed by "It is assumed that the levels given are mainbeam levels."
Basis: dBW/m2 power flux at the earth's surface, by harmonic
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0960
CLM-0960, Energy Aperture, as of 1975.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-111
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- Also from SRC-439
- CLM-0927The 1978 review found an interference route the report it was reviewing never considered: the power beam bouncing off rain, hail or blown...
- Also from SRC-451
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