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: http://www.arcetri.astro.it/irlab/luna/firpo/firpo_message7.html
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A new filter/box is available. It has been built by A. Bettarini, under contract from thr Arcetri Observatory. It is lighter, smaller and sturdier than the filter/clock and offset boxes used till now. Construction of a second model is foreseen in the near future. The box is a small plastic container, with two potentiometers and a push-switch. The two potentiometers allow the user to modify the offset (fine and coarse, +/- 0.5V and +/- 10V respectively). The offset is stabilized to a few parts in a million. The push-switch is used to select 4 fixed-cutoff filters, from 100Hz to 1000Hz (cutoff frequency shown on the box). Characterization of the filters is under way in the lab. Notice that only positions 0-3 are meaningful, while values of 4 and above will leave the signal unfiltered. The box has one input BNC, and two output BNC: one outputs the signal with the same polarity as the input, the other reverses the signal (remember that FIRPO has negative output). There is also a socket for the power supply, which is a separate component including the transformer.
Andrea