Value chain · CLM-1314
In plain terms
The international radio-astronomy standard says how weak a stray signal must be before it spoils a sensitive observation. In the radio-astronomy bands just above the 2.45 GHz and near the 5.8 GHz power-beam frequencies, that level is about 10^-24.7 and 10^-24.1 watts per square metre per hertz. Longer observations and satellites in geostationary orbit make it stricter still.
The claim as recorded
ITU-R RA.769-2 (2003) sets the interference levels detrimental to radio astronomy at the bands nearest the SBSP frequencies as -247 dB(W/(m2 Hz)) at 2695 MHz and -241 at 4995 MHz for continuum observations, each over a 10 MHz band (-177 and -171 dB(W/m2) in that band), and -255 at 1413.5 MHz (27 MHz band). Spectral-line thresholds are -239 at 1420 MHz (20 kHz channel) and -230 at 4830 MHz (50 kHz channel). All assume a 2000 s integration, a 0 dBi side lobe toward the interferer and a single antenna. The Recommendation gives no row at 2450 or 5800 MHz.
Evidence behind this: An ITU-R Recommendation, read directly: the internationally adopted criteria for interference detrimental to radio astronomy, not a regulatory limit. It is cited by the Radio Regulations framework, but this record does not establish its regulatory force.
Scope and limits
THESE ARE THRESHOLDS OF DETRIMENTAL INTERFERENCE, NOT REGULATORY EMISSION LIMITS. Applying them is left to RA.1513 (p.7), and no SBSP out-of-band emission level is given here. The band edges 2690-2700 and 4990-5000 MHz are inferred from centre and bandwidth; the edges are not printed on the page. Non-GSO cases need epfd and S.1428 integration (p.5, p.7), so a simple pfd comparison does not apply to them. In Table 1 at 10650 MHz the pfd column also reads -160, in dB(W/m2) per 100 MHz. That is not the register's -160 dBW/m2/Hz. The asof month is not on the page.
What it assumes
0 dBi side lobe (an angle of 19.05 deg on the SA.509 model, p.4); 2000 s; T = 22 K at these bands; terrestrial-source levels unless adjusted (p.6, section 2).
Where it comes from
Table 1 (PDF p.9) rows 1413.5, 2695 and 4995 MHz. Table 2 (PDF p.10) rows 1420 and 4830 MHz. Values above; recomputed from eq. 3-5 to within table rounding. Method, p.3: "An observing (or integration) time, t, of 2 000 s is assumed", and the threshold is the power that "introduces an error of 10% in the measurement of" Delta-P. Side lobe, p.4: "The gain of an isotropic radiator, 0 dBi, is used as a general representative value for the side-lobe level". The conversion from input power to pfd adds 20 log f - 158.5 dB (p.4, eq. 5; paraphrase). Corrections (Table notes, p.9-10; paraphrase): 10 h -6.3 dB; GSO transmitters -15 dB "desirable" (section 2.1, p.6). For satellite downlinks, p.7: "The limitations are, however, applicable to unwanted emission from the satellite transmitters, which fall within the radio astronomy bands listed in Tables 1 and 2." VLBI thresholds (Table 3, p.11): -205 at 2695 MHz and -200 at 4995 MHz.
Basis: dB(W/(m2 Hz)) spectral pfd and dB(W/m2) pfd in the stated RA bandwidth, 0 dBi side-lobe gain, 2000 s integration
Related records
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Cite this
energyaperture.com/c/clm-1314
CLM-1314, Energy Aperture, as of 2003.
Connected records
Other published records linked to this one. A list, not a judgement.