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More work at ISS #3 today. Due to the wet conditions and and a sore lower back, it was decided at breakfast to not take the clutter fence and radome off the 915 radar at Sedgwick this morning. Bill emailed this morning that we may be able to use the existing antenna since he compared its performance to the data from the radar at ISS #2 and saw good correlation between the two even though the system at ISS #3 was running at a lower power level (see Bill's comment on the ISS setup 27 March 2022 blog entry).
The final stage amplifier's current, and therefore output power, varies a lot for small changes in attenuation60 MHz input power. The system had been running with a lower power using 12 dB of attenuation (10 dB + 2 dB) and a final stage current of 1.02 Amps. I increased the power by decreasing the attenuation to 10 dB (removed the 2 dB attenuator), which produced a final stage current of 3.8-4.0 Amps. I wanted the current to be in the 3.5-3.6 Amps to match the power level of the system at ISS #2 and to make sure the final stage is not being overly compressed. I restarted the system and adjusted the 60 MHz Tx power level to get the desired current by adding a couple lengths of thinner coaxial cable in the line (no 1 dB attenuator attenuators available), producing a final stage current of 3.8 Amps upon initial startup, which is expected to decrease to near 3.6 Amps as the system heats up.
The system was showing very strong returns when started, likely due to the high humidity level/rain and rainwinds, so much so that the clutter seems to be suppressed in the display. Here are images of the display for each beam after the system was started showing the strong return levels.
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