I am having trouble using DC blocks. The DC blocks cause several resonances with the (transformers on the) ADC boards. Our test instruments have the danger of possibly adding DC offsets to their outputs. The ADC boards we use can be damaged by DC offsets. Thus, I use DC blocks on the inputs of the ADC boards when running tests and calibrations. Since I use the DC blocks during these test and calibration runs, the DC blocks remain on the inputs during experimental runs (with our antennas aimed at the sky) and I use calibration data to correct the sky data.
There has been some alarm in our group about resonances that cause the need to correct data. The sensitivity on one frequency channel may be different by a factor of several times compared to another channel less than 20 MHz away. Thus, I was asked to discover how other groups avoid this resonance problem. Already one person has indicated that the need for a DC block is eliminated by use of test equipment that cannot add a DC offset, but I am not sure we have such equipment for the frequency range we use (0-400 MHz). The purpose of the DC blocks was to make our test equipment effectively free from offsets. What do you suggest?
