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High spectral resolution observation of transitions in the LSB and USB mode of receivers revealed a shift of 0.5 channel towards lower or higher frequency depending on the version of the receiver (which defines the number of IF flips of the spectrum). The reference channel was always set to (N+1)*0.5 (N: Number of channels). If the spectrum was not flipped it has to be (N*0.5)+1 (N: Number of channels), if it is flipped N*0.5 (N: Number of channels).

This problem has been fixed in the control software. Below you can see two example spectra showing measurements in LSB/USB (in blue and red color) before and after the fix.

If needed this problem can be fixed for old measurements using the newest version of the EffelsbergSpecPipeline using the fixFFTSRefChannel() command:


fix/frequency_shift_in_ffts_observation_due_to_wrong_reference_channel.txt · Last modified: 2011/05/17 13:28 (external edit)