Overcast, rainy, and cooler today with highs only in the lower 50's.

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 60 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 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 winds, 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.

Vertical Beams WA0 & WA1

   


North-West & South-East Beams WA2 & WA4

 


South-West & North-East Beams WA3 & WA5


Liz arrived today and Bill arrives later tonight.   Tomorrow's forecast for Santa Ynez calls for sunny skies with a high near 67 and north-northwest winds of 10 to 15 mph with gusts as high as 25 mph.  We will see how the system runs tomorrow under the clearer and drier conditions.  Hopefully this will give Bill enough data to decide whether or not the antenna at ISS #3 needs to be replaced with the MISS antenna.





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  1. William Brown

    A quick comparison of the ISS2 and ISS3 profilers shows good agreement with winds.  The SNR is still lower for ISS3 although some of this might be due to lower precip at ISS3 compared with ISS2 (I don't have quick access to the precip data to verify if that is the case).


    Rancho Alegre ISS2 profiler on the left and Sedwick ISS3 on the right (NIMA processing).