Value chain · CLM-1045
In plain terms
Raytheon's own numbers had the klystron just failing the interference limit at the band edge and the magnetron clearing it by 45 decibels, while conceding nobody had measured a klystron that close to its carrier and that near the carrier the klystron was slightly quieter.
The claim as recorded
Raytheon's own klystron comparison, February 1981, states that the magnetron's noise inside the ISM band edges "is about 40 dB better than has so far been measured on klystrons in this same frequency region", that klystron noise has been measured by JPL at Goldstone "approaching 190 dB below the carrier at a frequency 180 MHz away from the carrier" but "there have been no noise measurements comparable to the magnetron so close to the carrier", and tabulates for a 7.7 GW transmitter the noise radiated in 4 kHz at the band edges as 0.00239 W from the "klystron data bank" against 0.00000075 W from the laboratory magnetron amplifier, a 31.3 dB and 66.3 dB margin over -154 dBW/m2 per 4 kHz on a hemisphere, becoming "-1.0 dB (4.06 sq. meters)" for the klystron and "45.5 dB (0.29 sq. meters)" for the magnetron once each element's aperture gain is applied; for close-in phase noise the 1980 report says the magnetron amplifier "is not quite as good as the example for the klystron".
Evidence behind this: T3-tube developer's own comparison, with the klystron entry unsourced beyond a footnote.
Scope and limits
The "klystron data bank" is not sourced beyond the Goldstone footnote and Figure 6-1's unlabelled band; the klystron entry is a mix of measurements at other offsets and frequencies, not a 2.45 GHz SPS klystron. The magnetron entry is CLM-1043's floor reading on one tube. The -154 is uncited (CLM-1050).
What it assumes
Noise radiated with the element's carrier gain toward the ground ("assuming the same gain for the noise as for the carrier signal", 0-8), and a hemisphere at about 3.7e7 m.
Where it comes from
PDF p.108 / 6-2, render read: "the noise level that is in the frequency region inside of the ISM band edges is about 40 dB better than has so far been measured on klystrons in this same frequency region ... their noise has been measured at levels approaching 190 dB below the carrier at a frequency 180 MHz away from the carrier* there have been no noise measurements comparable to the magnetron so close to the carrier"; footnote "*Measurements made by JPL on their klystron transmitting tube in the Goldstone tracking facility at S-band for deep space probes." Table 6-1 (PDF 110 / 6-4), render read: "TOTAL NOISE RADIATED POWER IN 4 KHz BANDWIDTH FROM 7.7 GIGAWATT TRANSMITTER 0.00239 WATTS 0.00000075 WATTS ... SAFETY FACTOR OVER CCIR REQUIREMENTS (-154 DBW/M2/4 KHz) 31.3 DB 66.3 DB SAFETY FACTOR AFTER TAKING GAIN OF RADIATING APERTURES INTO ACCOUNT -1.0 DB (4.06 SQ. METERS) 45.5 DB (0.29 SQ. METERS)". SRC-559 PDF p.51 / 4-13, render read: "It is not quite as good as the example for the klystron shown in Figure 4-5. (Note the 100 Hz bandwidth for the klystron data when comparisons are made)." Arithmetic on the stated figures: 0.00239 W / (7.7e9 W x 4000 Hz) is -161 dBc/Hz for the klystron entry; 4 pi A / lambda^2 at 2.45 GHz less 3 dB for the hemisphere reproduces the -1.0 and 45.5 dB.
Basis: watts in 4 kHz; W/m2 at earth; dB margin against -154 dBW/m2 per 4 kHz
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1045
CLM-1045, Energy Aperture, as of 1981-02.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-559
- CLM-1044In 1980 the quiet oven magnetron was already beyond the instrument's reach: at least 155 decibels below carrier per hertz away from the...CLM-1047The oven magnetron's second harmonic came out about 70 decibels below its carrier, a tuned stub took another 40 off, and the antenna's own...CLM-1048A cheap oven magnetron run cold and hard converted 81.7 per cent of its DC input to microwaves, measured carefully by heating water...CLM-1049The fifty-year magnetron rests on a cathode that runs cool because the tube heats it only as much as it needs, on tube-life curves from...CLM-1050The interference limit Raytheon measured its tubes against is given as a CCIR requirement but never traced to a CCIR document, and one page...
- Also from SRC-560
- CLM-1043With the heater off and a tuning circuit on the cathode, one hand-picked oven magnetron was as quiet as the instrument could measure: about...CLM-1046The number Raytheon wrote into the design table for the satellite tube was about fifty times noisier than its best laboratory reading...CLM-1047The oven magnetron's second harmonic came out about 70 decibels below its carrier, a tuned stub took another 40 off, and the antenna's own...CLM-1048A cheap oven magnetron run cold and hard converted 81.7 per cent of its DC input to microwaves, measured carefully by heating water...CLM-1049The fifty-year magnetron rests on a cathode that runs cool because the tube heats it only as much as it needs, on tube-life curves from...CLM-1050The interference limit Raytheon measured its tubes against is given as a CCIR requirement but never traced to a CCIR document, and one page...