Value chain · CLM-1047
In plain terms
The 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 pattern was credited with 65 more, so Raytheon reckoned the whole satellite's second harmonic would arrive on the ground fifty decibels under the limit. The third, fourth and fifth were measured but never filtered, and the fifth was unexpectedly strong.
The claim as recorded
Raytheon measured the oven magnetron's harmonics in 1980 on two QKH2000 tubes through a 7/8 inch coaxial output at 300 mA, 4000 V, heater off and 820 W into a matched load as -71/-69 dBc second, <-97/-85 third, -86/-93 fourth and -62/-64 fifth, against JPL's waveguide-method -56, -65 and -67 for the first three, called the fifth "suprisingly high", found a spurious n = 7 mode at 4360 MHz at <-100/-73 dBc, and showed a load mismatch shifting the fourth harmonic by more than 10 dB; in 1981 a coaxial stub tuned to the second harmonic gave "an additional 40 dB" on hot test, taking a second harmonic "approximately 60 dB below the carrier" to "approximately 100 dB", a third-harmonic stub could not be optimised alongside it and was removed, and Table 8-1 chains tube -61 dBc, stub -40 and slotted-waveguide pattern rejection -65 to -166 dBc per solid angle, -261 dBW/m2 at earth from one 0.55 m2 section and -204 dBW/m2 from 576,000 incoherent radiators at 7.5 GW against "-154" dBW/m2 per 4 kHz, which the text calls "a safety factor of 40 dB" and the table's figures make 50; orders three to five carry "NO DATA" in the filter column.
Evidence behind this: T3-tube developer's measurements on two tubes and one filter test, chained to the ground through an antenna pattern from a document not held.
Scope and limits
Two tubes, matched load; the source shows the level moves more than 10 dB with load. The 40 dB stub result is one hot test on one tube whose unfiltered second harmonic (about -60) differs from the 1980 pair's (-70). The -204 figure is a chain of one measurement, one filter test and one antenna pattern from another document, and the "no coherence" assumption is what turns 576,000 radiators into +57.6 dB rather than +115. The register's -154 comparator is uncited (CLM-1050). The 1980 summary's own third-harmonic average "-86" disagrees with its table's -91. The JPL second-harmonic figure is -54 dB where this record's table reads -56 (second reader, VER-1280). The text's "a safety factor of 40 dB" against Table 8-1's -204 and -154 (which make 50 dB) is the source's own text-table disagreement, read at the render (VER-1280), not a text-layer artefact.
What it assumes
Incoherent harmonic phase across 576,000 radiators, as stated; a slotted-waveguide pattern rejection of 65 dB at the second harmonic taken from JPL Publication 80-11, not held.
Where it comes from
PDF p.60 / 4-22, render read: "HARMONIC LEVELS #11 dbc #12 dbc f0 0 0 f1 <-100 -73 2f0 -71 -69 3f0 <-97 -85 4f0 -86 -93 5f0 -62 -64". PDF p.56 / 4-18, render read: "These compare with values measured by the techniques used by JPL of -56, -65 and -67 for the 2nd, 3rd and 4th harmonics, respectively. The 5th harmonic was not measured by JPL and its value as obtained by the Raytheon measurements is suprisingly high ... The magnetron power supply furnished 300 mADC at 4000 v to the tube which was operated at zero heater input and which delivered 820 W of rf power." SRC-560 PDF p.166 / 8-6: "the stub could be adjusted to reduce the second harmonic flow into the load by 40 dB. Because the second harmonic output was approximately 60 dB below the carrier without the use of the stub-line filter, the level of the second harmonic signal with the use of the filter was approximately 100 dB below the carrier ... An exercise with the measurements made on the second harmonic shows a safety factor of 40 dB at the earth." Table 8-1 (PDF 167 / 8-7), render read: "2ND -54 -70 40 65 -166 -261 -204 -154 / 3RD -65 -91 NO DATA 50 / 4TH -67 -89 NO DATA 50 / 5TH -63 NO DATA 65"; notes: "AREA OF ANTENNA SECTION IS 0.55 SQUARE METERS AND CORRESPONDING GAIN IS 26.7 dB ... 7.5 GIGAWATTS OF POWER OUTPUT COMPRISED OF 576,000 RADIATORS OF 0.55 SQUARE METER AREA. IT IS ASSUMED THAT THERE IS NO COHERENCE OF THE PHASE OF THE HARMONIC OUTPUT FROM THE RADIATORS."
Basis: dB below carrier by harmonic order; dBW/m2 at earth
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1047
CLM-1047, 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-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-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-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-1046The number Raytheon wrote into the design table for the satellite tube was about fifty times noisier than its best laboratory reading...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...