Cell Phone Detector birdie at 1548 Mhz
08nov06
Sections
Intro
Measurements
Conclusions
Plots
A new cell phone detector was purchased for the visitor center. We swept the detector in the screened room and found the largest birdie to be at 1548 Mhz. On 08nov06 we tested the detector using the telescope.
Measurements top
The cell phone detector was placed in the parking lot adjacent to the control room. The az, za position was set to 336,19. Lband wide was used to take the data. Two bands were centered at 1548 Mhz. The 12.5 Mhz band had 12.5 KHz resolution and the 390 KHz band haf 390 Hz resolution. Data was dumped once a second for 500 seconds. During the recording, the cell phone detector was turned off and then turned back on so we could see the birdie come and go.
The plots show the results of the measurements:
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Dynamic spectra with 12.5 Mhz bandwidth (.gif): The cell phone detector birdie is at 1548 Mhz.
The horizontal dashed lines are where the cell phone detector was turned off and then turned back on. When the detector was turned back on, the birdie frequency jumped by about 500 KHz. It took about 200 seconds for the frequency to return to 1548 Mhz.
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Dynamic spectra with 390 KHz bandwidth (.gif): This is the 390 Hz resolution data. You can see the birdie wander around prior to the turn off and the rapid drifting when it was turned back on. The width of the line is the inherent width of the line.
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Spectra of first and last record (.ps)
(.pdf): The first and last 1 second integration of the 390 Hz resolution data are plotted. The top plot is polA and the bottom plot is polB. The black trace is the first record, the red trace is record 500. The difference if from the drift. The width of the line is about 1.2 KHz.
Conclusions top
The new cell phone detector has a birdie at 1548 Mhz that can be seen in the lbw receiver when the cell phone detector is in the parking lot adjacent to the control room. The birdie strength is 15 Times Tsys in a 390 Hz channel width. If the cell phone detector is to be used at the visitors center, it needs to be put in a shielded box.
Processing: x101/061108/rfi.pro
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