Value chain · CLM-1413
In plain terms
A 1977 NASA-funded report says the metal mesh behind a receiving station's antennas can be about three-quarters open to light while letting through only about half a per cent of the microwave power. The 1978 reference design used a steel mesh about that open.
The claim as recorded
JPL's 1977 microwave subsystem report states that a rectenna ground plane of wires in a grid, or with holes, can be up to about 75% optically transparent at normal incidence before the RF power leaking to the back side approaches 1/2%, and names aluminium or galvanised steel wire mesh for the ground planes; the 1978 Reference System describes a steel mesh ground plane of 75-80% optical transparency. SRC-450 says that "if the ground plane is composed of wires in a grid or holes or other perforations, the openings can represent up to about 75% optical transparency at normal incidence before the RF leakage to the back side approaches 1/2%", and that "The dipoles and dc collection buss further reduce the optical transparency to ~60%". Its rectenna element includes "aluminum or galvanized steel wire mesh ground planes". SRC-085: "Each panel has a steel mesh ground plane with 75-80% optical transparency", with "a small amount of RF energy leakage through the ground screen".
Scope and limits
A DESIGN STATEMENT, NOT A MEASUREMENT. SRC-450 gives no mesh pitch, wire size, frequency-specific geometry, test or reference for the 1/2% figure, and states it for normal incidence only; it does not say whether "approaches 1/2%" is a ceiling at 75% or a rough value. SRC-085 gives no leakage figure and no wire size or pitch. Neither page says the 1977 NASA study's 1 x 2 cm diamond openings (CLM-1409) give 75% transparency. "Leakage to the back side" is a share of the power reaching the ground plane; how much reaches it past the dipoles is not stated.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF 83 [3-22] to PDF 84 [3-23], raw across the page break: "For effective RF performance, if the ground plane is composed of wires in a grid or holes or other perforations, the openings can represent up to about 75% optical transparency at normal incidence before the RF leakage to the back side approaches 1/2%." PDF 84, raw except "~" for the page's tilde: "The dipoles and dc collection buss further reduce the optical transparency to ~60%." PDF 84, section 3.3.3.1, raw: "aluminum or galvanized steel wire mesh ground planes and current collecting lines". SRC-085 PDF 49 [37], raw: "Each panel has a steel mesh ground plane with 75-80% optical transparency."; "There will also be a small amount of RF energy leakage through the ground screen".
Basis: per cent of incident power; optical transparency at normal incidence
Cite this
energyaperture.com/c/clm-1413
CLM-1413, Energy Aperture, as of 1977-09.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-085
- CLM-0013The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per...CLM-0020The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at...CLM-0023In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed...CLM-0039The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and...CLM-0045The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0137In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam...CLM-0138The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency...More on the source page.
- 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-0951The 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...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...