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					Drive-by, Stand-by 3.2 Ton Forklift Line-of-Sight Tag Blockage Test
Wednesday, June 11, 2008 Version 1-1
Visible Assets, Inc. 195 Bunker Hill Ave. Stratham, Inc

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Purpose + Methods
Demonstrate affects of placing a large piece of steel in the magnetic field of a RuBee network. We placed a test tag 8 feet from a RuBee ToughPak reader and pinged it at 6-7 reads per second. Placed second tag on the forklift We drove the Forklift between the test tag and ToughPak to block line-of-sight transmission. We parked the Forklift in middle of test tag’s line-of-sight 15 seconds to collect statistics

Visible Assets, Inc. 195 Bunker Hill Ave. Stratham, Inc

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The Test Configuration
Forklift Tag IP = 37 ToughPak RuBee Router RuBee Rod Antenna

Test Tag IP = 36

3.2 feet

8.5 feet Forklift Tag
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Test Tag
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1.5 Mph Drive-by Test
Signal Strength vs Time during Drive-by
Forklift Tag IP = 37 Test Tag IP = 36

Control Tag 38 Noise Note: Blue = Forklift Tag CRC Check: Red = miss-read Green = Test Tag CRC Check Green: Red = miss-read
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1.5 Mph Drive-by Test II
Signal Strength vs Time during Drive-by
Forklift Tag IP = 37 Test Tag IP = 36

Enhanced Field Distortion Bump Note: Blue = Forklift Tag CRC Check: Red = miss-read Green = Test Tag CRC Check Green: Red = miss-read
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Stand-by Test Statistics
Forklift Tag IP = 37 Test Tag IP = 36

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Conclusions
A 3.2 ton John Deere forklift placed directly between a RuBee reader and a RuBee tag (100% line of sight blockage) reduces the tag’s signal strength by about 23% (mean 578 SUs to mean 447 Sus), however the forklift blockage did not lead to tag miss-reads or a significant loss of performance within reasonable ranges. As the forklift bucket approaches the tag’s line of sight the signal strength consistently increased by as much as 30%. This was likely due to the steel bucket’s location directly below the line of sight, however more work must be carried out to confirm details. Large steel bodies clearly do distort RuBee’s magnetic field, but that distortion does not appear to significantly alter tag performance under normal conditions.

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Description: drive by stand by forklift test