Documentation:

• SmartIIs users guide (.pdf)
  

see also:

• Evaluating compliance with FCC guidelines for human exposure to radio frequency electromagnetic fields.
• Aug2005: Site RF safety report from RF consultant (.pdf)

History:

• 04mar13: sign of output flipped to give positive output.
  
• 28feb13 new rf monitor installed
  

28Feb13:new rf monitor installed.

    A new rf monitor was purchased  and installed at the visitors center on 04feb13. 

The plots shows the output from the monitor for 17feb13 (.ps) (.pdf)

• The vertical scale is fraction of allowable exposure for humans in a non controlled environment
• I think we chose the jumpers so that  1 on the plot = 50% of maximum allowable exposure.
• I looked at data from 05feb13-28feb13. 17feb13 was a typical day (except that it included the sband transmitter 21:22 hours ast).
  
• Top: this is the raw data recorded in the file.
• The value is always negative, and decreases toward noon.
• I think the value should always be positive so my guess is that the sign is inverted
• Bottom: I've multiplied the plot by -1.
• The signal starts to increase around 8 am and peaks around noon.
• The dashed red lines show when the sband transmitter was on (not sure what the power level was). It looks like the transmitter is registering on the meter.
  

• A solar flux unit is sfu
  
• 1e-22 W/m^2/Hz.  The radiation standard used milliwatts/cm^2 so
• 1e-23 mW/cm^2/Hz ..
  
• Looking at radio flux measurements of the sun give values like:
• 432Mhz =38 sfu
•  1296 Mhz 84
• 2300 Mhz 92 sfu
• 3300 Mhz 101 sfu
• 5650 Mhz  157 sfu
• 10368 Mhz 337 sfu
• 15400 Mhz 576 sfu
• As a worse case assume we integrate 0 to 100Ghz with an sfu=1000.
• 1000sfu*100e9Hz= 1e-9 mW/cm^2 integrated.
• I'm assuming that sun output 15400 -> 100,000 Mhz doesn't increase so much that the 0-100Ghz avg does not go above 1000sfu
  
• The monitor output is in fractions of allowable human exposure.
  
• We've asked for the uncontrolled access limits on our monitor:
• .3-1.34 Mhz : 100 mW/cm^2
• 1.34-30 Mhz: (180/Frq^2) mW/cm^2
• 30-300 Mhz  : .2 mW/cm^2
• 300-1500 Mhz: frq/1500 mW/cm^2
• 1500-100,000 Mhz: 1.0 mW/cm^2
• So the max allowable maxes out at .2 mW/cm^2  so our integral above could be multiplied by 5 or 10 to get the fractional allowable radiation from the sun.
  
• The monitor antenna looks to be a few cm^2..
  
• So the sun worse case would be 1e-8 times the allowable maximum. So we shouldn't see it.
• The change in output may be a thermal issue (with either the meter, or the sbc computer with a/d that is being used to record the data).
  
• The monitor is inside a plastic box mounted about 10 feet up on the south facing wall of the visitors center.
•  I stood below it for a few minutes at the beginning of feb13 and i felt pretty hot.

processing: x101/130228/chkmon_feb13.pro

29jun12: daily RF monitor day for feb09:

    The RF monitor data for each day of feb09 was plotted. The data processing was:

• Median filter each days 1 seconds to 1 minute

• I've scaled the Y axis to be the maximum allowed exposure (most plots in the other sections are .5*(maxexposure))
  
• Top frame:
• All 28 days are over plotted.
• It gets up to about .24 of max allowable around 10am (i don't know whether this is the sun or not?)
• Bottom:
• Each day has been plotted with an offset to separate out the days.

• You can see the peak strength 11feb09 around 10am
• The vertical strips are dropouts. For the line plots above, i excluded these points (since they covered up the other data).
  

29jun12: RF monitor data:(1st day of each mon:feb09-jun12)

•  Plots were made ( pwr vs time) for the first day of each month.
  
• The y scale is .5*(the maximum allowable exposure). When the scale reads 1., you are at 50% of the maximum allowable value (i think the device is set for controlled access areas).
• The data was median filter by 13 samples to remove the glitches that occur every 47 seconds (see 23Aug06 discussion below)
  
• The table gives a brief summary of the 1st day of each month. The codes used are:

• DP  - data present.
  
• ND - no data
• 0's   - data all zeros
• NC  - cable not connected

• These notes only refer to the 1st day of each month.. I didn't look at every day of every month..
  
• 2009
• data present for most months.
  
• Dropouts occur 11:am to 3:pm on some days
• no data apr09
• 2010
• Most of the 2010 data is garbage.
• 2011
• No good data 2011
• 2012:
• not data for jan,feb then unplugged mar-jun12..
  
• Jun12 the monitor was taken down to the lab. It was full of water. Someone opened the waterproof box to unplug the cable (so it would stop beeping, and they didn't close the waterproof box correctly..).
• We need a new monitor.
• We currently have a narda smarts II model A8830. It has a safety profile for controlled access areas. For the visitor center we should probably buy the D8830 which i think has a profile for uncontrolled access areas.
• A new monitor costs about $3500.
  

23Aug06: Test monitor which 430 Mhz transmitter.

• lf: line feed transmitter
• gr: gregorian dome transmitter
• az (xx): the azimuth is  the physical location of the transmitter. 180 (xx) is always on the far side, 0(xx) is always on the near side.

The RF monitor output goes  from 0 to 1 and is linear in power. The value 1. corresponds to a power level that was 50% of the maximum allowable value (weighted by frequency range).  So a value of .1 would be .05 time times the maximum allowable value.
NOTE: later it was found that the meter is using the wrong radiation profile (see below). It uses a maximum values that is 5 times too high. Given a value on the plots, you should multiply it by 2.5 (5/2) to get the fraction of the maximum allowed value. A value of .1 would be .25 of the maximum allowed value.

The first set of plots shows the  RF monitor power versus time (.ps) (.pdf):

• Top: The rfmonitor power versus time 4:00 to 14:00.
• Black was taken on 23Aug06 (the day of the test).
• Green was taken on 22Aug06 (the previous day when the transmitter was not on).
• The red vertical lines show the time when the xmter was on during 23Aug06.
• On both days the reading is quiet until around 6 am. It rises and begins to oscillate (with a period of about 45 minutes).
• The level rises to about twice the morning value at 12:00. It comes back down to the nighttime value around 14:00.
• Middle: rfmonitor power vs time 10:00 to 14:00 xmiter on.
• This is a blowup of the 23Aug06 data during the xmiter tests.
• The black data is the RF monitor.
• The green data was taken during the first test (lf, za=19.5, far side)
• The blue data was taken during the 2nd test (lf, za=19.5, near side)
• The purple data was taken during the 3rd test (lf, za=15, near side)
• The light blue data was taken during the 4th test (gr, za=19.5 near side).
• The red solid line  shows the transmitter power. It came on about 11 am. It went off about 13.25. The dashed red line is a tx power of 2 MW.
• The RF monitor level did start to rise when the xmter came on. It went back down before the xmter went off (it did start to move in azimuth). This bump may or may not be caused by the xmter.
• Bottom: azimuth vs hour of day.
• The azimuth position (dome side) during the tests. The colored areas show when the tests occurred.

• Top: test 1. Linefeed far side, 19.5 za. You can see an increase in the power level when the azimuth is at 187. This is when the line feed is aligned 180 degrees from the radiation monitor. The increase is about .02/.10=20%. The absolute value of the increase is .02*50%= .01 of the maximum allowable value.
• 2nd test 2: linefeed near side, za = 19.5. There is no noticeable azimuth dependence of the power.
• 3rd test 3:  Linefeed at near side, za=15. No azimuth dependence of the power.
• 4th test 4: dome at near side, za=19.5. No azimuth dependence of the power.

Glitches in the RF monitor:

Summary:

• The measured power value of the RF monitor changes by a factor of two day to night. The levels peak around noon. The device output may be changing with temperature.
• We saw a small change in the power level versus azimuth when the dome was on the far side and at 19.5 degrees. We did not see any azimuth dependence of the power when the transmitters were on the near side.
• There was an increase in the power level when the transmitter started to come on. The change was a slow rise (10 to 15 minutes). There were no sudden jumps when we increased the transmitter power (usually this took a minute or two).
• The RF monitor is seeing glitches that go full scale every 46 to 48 seconds.  They stay high for 1 or 2 seconds and then undershoot for 3 or 4 seconds. They were not there in the lab or when the device was covered with a mesh. We need to determine whether this is real or a glitch in the device. The alarm in the control room is not being triggered by these glitches so the alarm must be disabled.
• The power levels measured by the RF monitor do not agree with the hand held RF monitor. The hand held monitor read a maximum value of .12 mW/cm^2. This is 41 % of the maximum allowed value at 430 Mhz (using .29 mW/cm^2).  The maximum value read by the RF Monitor was .13 *(50% of max allowable Value) = 6.5%  . So the two devices differ by a factor of ..41/.065=  6.3.  This discrepancy  is probably coming from the standard being used by the fixed RF monitor : fcc 1997 occupation/controlled.
• For uncontrolled access areas the 430 Mhz limit is 430/1500=.29 mW/cm^2
• For controlled access areas the 430 Mhz limit is 430/300 = 1.43 mW/cm^2
• The ratio of these values is 5 which agrees with the measured difference above.
• Taking the above into consideration, the power levels on the plot should be multiplied by 2.5 to get the fraction of allowable radiation.
• We need to switch the RF Monitor to use the uncontrolled/general population access RF limits for the visitors center overlook.
• Current model:
• A8830: FCC 1997 occupational/Controlled access
• What we should have is uncontrolled access. Probably:
• D8830: ICNIRP 1998 or ENV 50166-2 Occupational.
• 
  

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