25oct13. Here are my latest plots of the sliding shutter performance... The 'CLOSED' plot data is identical to that on the plot I sent yesterday (Thurs 24 Oct 2013). The only changes are a couple of minor cosmetic variations. The 'OPEN' plot data are for the same zenith angles and still for beam 3B, but this time the sliding shutter is OPEN. Despite my misgivings about the close call at 2375 MHz with the shutter closed, it is clear that the shutter is doing a lot of good. Note that both plots show a lot of rather fine structure on the general scale of about 1 to about 10 MHz. However, with the shutter closed there seem to be some additional resonances, with the principal one obviously contributing strongly to that worrisome close call. My comments of yesterday notwithstanding, I'm now thinking that it would be worthwhile to first take data with the old manual shutter bolted on, for comparison. If we leave off the bar, we should be able to take this data at the same ALFA rotation angle as used for taking data with the sliding shutter. Cheers, Dana