Value chain · CLM-0951
In plain terms
The usual way to stop a strong transmitter interfering with other radio users is to smear its power across a wide band. For a solar power satellite the report calculates that the smear would have to be about 3200 GHz wide to satisfy the protection limit for microwave relay links - about 32,000 times the 100 MHz band the satellite would use. The beam is strong enough to overload a relay receiver even at frequencies well away from its own.
The claim as recorded
Spectrum spreading, the standard remedy for an interfering carrier, fails against the SPS power beam by a margin that has to be stated against something, and the same document supplies the comparator: the ISM allocation the SPS would use is 100 MHz wide, emissions confined within +/-50 MHz of 2450 MHz (SRC-450 p.32, quoted at CLM-0919), and the spreading required is 3200 GHz - a factor of about 32,000. Verbatim: "A common technique for reducing PSFD is spectrum spreading. If the SPS power were uniformly spread in frequency it would have to occupy approximately 3200 GHz in order to meet the LOS protection criterion." The same page states the scale of the problem it would have to solve: at 2450 MHz, for a line-of-sight relay antenna with RF entry at the 0 dBi gain angle, "the interfering signal would be -94 dBW or -64 dBm", which "is sufficient to cause overloading interference effects even when considerably removed from the LOS frequency of operation". And of the emission spectrum generally: "Note that harmonics appear to pose an especially severe problem."
Evidence behind this: T3-primary-report, and appropriate: this is the SPS programme's own assessment of a mitigation it might have wanted to work, which is the version of that judgement least likely to be pessimistic.
Scope and limits
THE 3200 GHz IS AN ILLUSTRATIVE CALCULATION, NOT A DESIGN STUDY. The report gives it in one sentence with no working, and this record does not reproduce the arithmetic because the inputs are not all on the page. IT IS ALSO AN ARGUMENT AGAINST UNIFORM SPREADING SPECIFICALLY - the sentence says "uniformly spread" - and says nothing about shaped spreading, notching around protected bands, or siting and pointing remedies, none of which the passage considers. NOTHING HERE ESTABLISHES WHAT A MODERN DESIGN WOULD NEED, since the protection criteria quoted are 1970s CCIR and IRR values and the register holds no current edition of either. THE -94 dBW FIGURE IS FOR ONE GEOMETRY - a specific antenna, gain angle and frequency - and is not a general statement about relay receivers. CORRECTED 2026-09-15 ON VERIFICATION: the claim had said "about three orders of magnitude" with no comparator in the support - a magnitude that had become an adjective, A66's fourth limit exactly. The comparator now named is the allocation width from the same document; against the whole radio spectrum in practical use it would be a different and smaller ratio, and the record does not choose that one because the document does not.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
All three spans read from SRC-450 PDF p.34 on registration. The spectrum-spreading sentence and the overload sentence match at the normalised level; "Note that harmonics appear to pose an especially severe problem" matches RAW. The protection criterion being tested is stated on the preceding page as an upper limit between -154 and -144 dBW/m2 in any 4 kHz band near 2 GHz depending on arrival angle - that span matches only after depunctuation and is therefore reported, not quoted. THE COMPARATOR, QUOTED HERE RATHER THAN BY REFERENCE, ADDED 2026-09-15 ON VERIFICATION. SRC-450 PDF p.32, verbatim at the normalised level: "The frequency 2450 MHz is designated for industrial, scientific and medical purposes ... Emissions must be confined within +/-50 MHz of the frequencies designated." That is the 100 MHz width the ratio is taken against.
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0951
CLM-0951, Energy Aperture, as of 1977.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-450
- CLM-0949There is a standard international curve describing how quickly an antenna's stray radiation should fall away off-axis. The SPS pattern...CLM-0950A solar power satellite in geostationary orbit cannot make its beam any tighter than its design figure, because it is too far away to focus...CLM-0952A solar power satellite would have to stay below published interference limits, and the limits differ by who is being protected. Microwave...CLM-0969If the tubes are only 70 per cent efficient, the transmitter's own face is not big enough to get rid of the heat they make, even spread...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...CLM-1413A 1977 NASA-funded report says the metal mesh behind a receiving station's antennas can be about three-quarters open to light while letting...