Passive filters involve the design of one or more low-pass LC filter traps, each trap being tuned as required to a harmonic frequency ( 5th, 7th, 11th, 13th, . . . kq + /-1, where k = integer, q = pulse number of converter ).
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As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F _ R, called the Nyquist frequency, since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring:
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They worked with Washington and the result was that amateurs received the orderly series of harmonic frequency bands that they largely hold today ( originally 1.8, 3.5, 7, 14, 28, and 56 MHz; other bands have since been added and the 56 MHz allocation was changed to 50 MHz ).
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:Just a guess, bit if they had a vibration problem due to the hard drive hitting it's natural resonance frequency, then adding a metal ring like that to change it's mass, and thus it's harmonic frequency, might be the quick and dirty way to solve the problem . talk ) 17 : 57, 29 March 2014 ( UTC)
