Value chain · CLM-1046
In plain terms
The number Raytheon wrote into the design table for the satellite tube was about fifty times noisier than its best laboratory reading, because it did not yet know where the noise came from; the only work on that question was Raytheon's own unfunded research.
The claim as recorded
Raytheon's projected electrical characteristics for the SPS magnetron package, February 1981, put its noise at "-120 DBC/MGZ" (dB relative to carrier per MHz, the page's own misprint) 30 MHz from the carrier, determined by "Unresolved Determination of Noise Sources and Their Elimination" - 17 dB worse than the -196.8 dBc/Hz measured on the laboratory tube (-120 dBc/MHz is -180 dBc/Hz) - with added phase noise -114 dBc per kHz at 50 kHz "Measured", operating filament power zero "Reduction of Noise", starting filament power 70 W; and the report lists as its first two unresolved issues "An understanding of the residual sources of noise in the microwave oven magnetron and how they may be controlled" and "of the sources of inefficiency", stating that "the only supported activity toward a better understanding of the causes of noise and reduced efficiency was a Raytheon Independent Research program".
Evidence behind this: T3-tube developer's design projection for a tube never built.
Scope and limits
A projection for a tube never built; the -120 is stated without derivation. Item 14's unit is truncated on the page to "-114 DBC/" and is read as per kHz from SRC-559's 1 kHz measurement.
What it assumes
That "MGZ" is MHz, which the table's per-Hz-to-per-MHz convention on 6-15 (136.8 dB/MHz) supports; -180 dBc/Hz is a conversion of the stated figure.
Where it comes from
Table 7-3 (PDF 157-158 / 7-29 to 7-30), render read: "13 Noise 30 MHz from Carrier -120 DBC/MGZ* Unresolved Determination of Noise Sources and Their Elimination See Section 6.0 of this Report *DBC - decibels relative to carrier power." "14 Added Phase Modulation Noise 50 KHz from Carrier -114 DBC/ Measured" "15 Starting Filament Power 70 Watts" "16 Operating Filament Power 0 Reduction of Noise". PDF p.24 / 0-10: "1. An understanding of the residual sources of noise in the microwave oven magnetron and how they may be controlled. 2. An understanding of the sources of inefficiency in the microwave oven magnetron and how they can be eliminated." PDF p.180 / 10-4: "the mechanisms responsible for a seemingly large variety of observed noise have not yet been identified ... the only supported activity toward a better understanding of the causes of noise and reduced efficiency was a Raytheon Independent Research program".
Basis: dB below carrier per MHz and per kHz, projected
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1046
CLM-1046, Energy Aperture, as of 1981-02.
Connected records
Other published records linked to this one. A list, not a judgement.
- 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-1045Raytheon's own numbers had the klystron just failing the interference limit at the band edge and the magnetron clearing it by 45 decibels...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...