14feb13: ELO emissions in the screen room:

    The setup was:

The plots show the rfi from the system with the cash register  on and off (.ps) (.pdf):

• Pages 1,2:
• each 100 Mhz band is plotted in a different color
• 0-3000 Mhz was split into 3 1000 GHz sections.
• For each pair of frames, the top frame is cash register on and the lower frame is cash register off.
• For some freq ranges, there was more rfi in the off than the  on .
• Page 3: 100 Mhz blowups of 200-300,300-400,400-500 Mhz
• 200-300
• There is a 6.181Mhz comb that peaks at 245.83 Mhz.
• the strong birdie at 237.821 had harmonics at 475.9,713.385,951... 1426.77 Mhz
•  has a harmonic at:k

A table of the strongest birdies:

freq Mhz	amp dbm	notes
237.821	-84	probably part of a 39.6457Mhz comb that is seen up to 1427.1651
245.83	-90	part of a 6.182 Mhz comb
327 receiver
317.06	-100	part of 39.6457 comb
475.825	-91	part of 39.6457 comb
1427.1651	-113	part of 39.6457 comb
1500	-97

processing: x101/rfi/miscdevice/eloCashReg_130306/cashdata.pro

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22mar13: Emissions seen on the telescope.

    On 22mar13 the the emissions from the cash register was measured on the telescope using the 327 receiver.
The setup was:

• 327 receiver used with center frequency at 317 Mhz.
  
• The cash register was placed in the middle of the patio in front of the control room (where the scribe marks in the concrete cross). It sat on top a small table (about 3 feet off the ground).
  
• The telescope was positioned to az=333.2, za=17. Previous az swings showed this to be the peak azimuth for this position (and the dome at za=17).
• The interim correlator was used with 1024 channels, 12.5Mhz bw, on second integrations, 9 level sampling, and hanning smoothing.
• Data was taken for 300 seconds.
• The first 160 seconds had the cash register on, the final 140 seconds had the power off to the cash register

After the datataking with the telescope, the  Rhode&Schwartz spectrum analyzer was used to measure the field strength at the cash register. The setup was:

• preamp on, rms detector, 2 Mhz bandwidth, rbw=10Khz, vbw=100 Khz (avg 10 sweeps), attenuation=0
• a 3 meter bnc cable connected the 904 Efield probe to the spectrum analyzer.
• The probe was placed next to the strongest emissions from the cash register (by the power cable connection to the device).

A dynamic spectra of the 300 seconds of data on the telescope was made (.gif):

• The dashed horizontal line shows where the power plug was pulled from the cash register
• The birdie at 317.155 MHz disappeared at this point.

Average plots of the cash register on and off were also made (.ps) (.pdf):

• Top Frame: Black: average (160 secs)  cashReg on, Red: average cash register off(140 secs). the dashed green line is the birdie at 317.155
• 2nd Frame: On/off -1. This shows the birdie strength in units of Tsys (about .008 Tsys).
• Bottom: Strength of the cash register emissions using the Spectrum Analyzer and the 904 Efield probe.
• The probe was placed write next to where the power cord connected to the device.
• The peak was -97dbm. It corresponds to the birdie seen in the telescope.
• When the probe was moved away from the cash register, the birdies disappeared (so it was not coming from some other source).
  

processing: x101/130322/rfitest.pro

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Summary:

• Cash reg has very large rfi in 200-300 Mhz range.
• There are birdies seen up to sband.
• In our receiver bands the strongest birdies are:
• 327 = 317.155
• lband 1500 Mhz
  
• With the cash register sitting on the patio in front of the control room, the 317.155 birdie was seen  in a 24Khz bw, 1 second integration.
• A -97dbm birdie (10Khz rbw) seen with the 904 Efield probe adjacent to the device can be seen in the telescope with a 1 sec, 24Khz bw when placed on the patio of the control room.
• This device can probably be used in the cafeteria (since there is extra path loss).
• More tests should be done before this device is allowed at the visitor center.

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