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ISS3 (Sedgwick): More diagnosing of the problems with the wind profiler. John did some return loss and frequency response measurements on the antenna and some of its elements. He found that the peak response of the antenna was around the 905 - 909 MHz range instead of the 915 MHz that is should be. It appears to have drifted over time for some reason. There is some dust and dirt on the antenna, but wiping a small section didn't help the unlying elements so perhaps the antenna substrate has degraded. It may be that this is causing the more significant return loss seen on this antenna as compared to the ISS2 antenna (something around 30% as compared to around 5% at ISS2). The stronger signals being reflected in the antenna may be bouncing back into the front-end receiver chain showing up as clutter like signals. He added a second circulator and limiter to try to suppress it, but that doesn't seem to help.
