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Several other tests were performed on the system today to verify operation. First, the LO power levels at the input to the RFE troughs were checked. They measured +10.7, +10.6, and 10.7 dBm for Channels 0, 1, and 2, respectively. The mixers in the troughs are Mini-Circuits ZFM-15-S+ that have a nominal required LO level of +10 dBm, so LO levels are good.
SecondlyNext, the receiver gains were measured by using the portable Anritsu VNA in CW mode with several attenuators on its output to inject a very low level CW signal at 449 MHz into the antenna port of the Tx/Rx circulator cables in the RFE troughs and the resulting 60 MHz RF powers measured at the Pentek inputs using an oscilloscope (Vrms measured and power calculated as P (dBm) = 10*log10(Vrms^2/50)+30). The exact value of the RF signal injected into the Tx/Rx circulator is not known because the signal level is too low to measure, but is estimated from the measured output power of the VNA and the nominal values of the attenuators used, which was ~-66 dBm today. The measured Rx gains were 51.5, 51.2, and 51.9 dB for Channels 0, 1, and 2, respectively. This shows that all three receive channels are functioning in a similar manner, meaning there are no bad components in the chains. Also, these numbers are comparable to the ~54 dB of gain measured during the SAVANT field project. Thus, the receivers are deemed to be operational.
Third, the LO out of the RIM box was connected directly to the portable Anritsu spectrum analyzer to check that the RIM functionality was working. The spectrum is shown in the image below (once I get it uploaded). The four frequencies seen match the frequencies displayed on the front of RIM box. RIM functionality is operational.
Next, the length of the HPA Gate signal was adjusted slightly such that the tail of the RF pulse was clipped cleanly as seen in the images below.
A new range calibration was then conducted. One had been conducted earlier but the test pulse was found to be off by ~300m. 96 counts were added to the Rx Delay to compensate for the 96 counts added to the Tx Delay earlier this week (which allows time for the RIM frequencies to fully switch before the Tx pulse is generated). The range test pulse is now centered in the 3073m gate.
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Images of the configurations screens for the SWEX profile are shown below for reference.
