Value chain · CLM-0927
In plain terms
The 1978 review found an interference route the report it was reviewing never considered: the power beam bouncing off rain, hail or blown sand into a ground microwave receiver that happens to share the frequency. It calculated the result and found it far above what international rules permit as unwanted signal. It also picked out the third harmonic, at 7350 megahertz, as the one most likely to cause trouble, because it lands in a government satellite band.
The claim as recorded
The March 1978 review identifies a PRECIPITATION-SCATTER interference path that the Battelle assessment does not treat at all: the SPS beam scattering off rain, melting hail or airborne particles into a co-channel terrestrial microwave receiver, computed through the bistatic radar equation at a 45 degree scatter angle, 40 dB receiver gain, a 0.025 radian beamwidth, 5 km range and a moderate 10 mm/hr rain rate. It states that both the rain and melting-hail results are "values well in excess of ITU requirements for maximum permissible unwanted signal level at 2.45 GHz", and that the ITU values "run more on the order of -140 dBw". A worked sandstorm case, at 0.1 cm particle radius and rain-equivalent concentration, gives "about -58.4 dBw" - roughly 82 dB above the limit the same paragraph cites. Separately, on harmonics, it identifies the third harmonic at 7350 MHz as falling in the 7300-7450 MHz band allocated for government fixed-satellite, fixed and mobile use, and judges that this harmonic "probably has the greatest potential of any of the harmonics for causing concern".
Evidence behind this: Federal agency review, read directly in the held file. Quotations confirmed with whitespace removed, because the text layer letterspaces. THE NUMERIC RESULTS OF ITS DISPLAYED EQUATIONS ARE NOT IN THE TEXT LAYER AT ALL - the prose reads "Then, using (2) through (6), we obtain" and "Whence," with nothing following, because the results are rendered as images. Figures for equations (7) and (9) are therefore render-only and are NOT recorded here.
Scope and limits
THE RAIN AND MELTING-HAIL RESULTS THEMSELVES ARE NOT RECORDED HERE BECAUSE THEY ARE NOT IN THE TEXT LAYER. The document's displayed equation results are images; a reader wanting those two numbers must open the page. What IS recorded is the document's own verbal characterisation - "well in excess" - and the one worked case that survives extraction. THE SANDSTORM CASE IS A CONSTRUCTED EXAMPLE, at an assumed particle radius and a concentration assumed equal to rain, "for a fully-filled common volume" - it is an illustration, not a measurement, and the 82 dB inherits every one of those assumptions. A 1978 review of a 1977 draft, using 1976 ITU requirements which have since been revised. Nothing here establishes that any real receiver was or would be affected - the common volume is assumed fully filled and the geometry is chosen, not observed.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
Read first-hand on registration; confirmed with whitespace removed. Inputs verbatim: "Suppose we now consider scatter at 8 = 45", and let us choose other (presumably reasonable) values; namely r = 104 (40 dB), and = 0.025 radian (-1.5"), r = 5 km and a moderate R = 10 mm/hr." Verbatim: "In any case, both (7) and (9) are values well in excess of ITU requirements for maximum permissible unwanted signal level at 2.45 GHz (ITU, 1976). These values run more on the order of -140 dBw. Of course, atmospheric attenuation may reduce the values of (7) and (9) some when it is accounted for in (2), but not nearly enough." Sandstorm case verbatim: "about -58.4 dBw would result at the MWS, again, for a fully-filled common volume." Third harmonic verbatim: "4.2 Third Harmonic 7350 MHz This harmonic is in the band 7300-7450 which is allocated for Government use for fixed-satellite (space-to-earth), fixed, and mobile. As will be seen, this harmonic probably has the greatest potential of any of the harmonics for causing concern." THE 82 dB IS THIS REGISTER'S ARITHMETIC on the document's own -58.4 and -140, not a figure it states.
Basis: dBw (received unwanted signal); MHz (harmonic frequency)
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0927
CLM-0927, Energy Aperture, as of 1978-03.
Connected records
Other published records linked to this one. A list, not a judgement.