Injection system (General activities)Paoletti - 17:46 Thursday 16 June 2011 (29675)
Print this report (29672)During the "sniffing" action of 3kHz source, likely in crates of DSP PR and INJ, we've also checked with a portable spectrum analyser (battery powered) the output of the box that give the Bs_MOD_6MHz signal to both ADCs (Pisa ADC located in C40 Daq room rack and propagated using BNC cables and 20KHz ADC7674 located in the EERoom).
The signal was very clean (no 3kHz lines) as visible in ADC7674 when the Bs_MOD_6MHz was unplugged from Pisa ADC.
This confirm that the 3kHz lines are "fake" (= no present in the Bs_MOD_6MHz).
However there were two lines equally spaced (~18Hz) around 50Hz, both clearly visible in the same signal at the same time; they are indeed real.
This means that the Virgo modulation index could be "modulated" at 32Hz and 68Hz.
Comments to this report:
tournefier - 9:48 Friday 17 June 2011 (29680)
Print this reportThe structures around 32 and 68 Hz are known to be amplitude modulation noise: see Modulation/demodulation noises.