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Antenna 101 Basics 2010 Advance Train the Trainer Starts @ 0800

Antenna 101 Basics 2010 Advance Train the Trainer Starts @ 0800. A fairly small amount of information and educational material can go a long way toward preventing unnecessary alarm or concern to workers and others.

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Antenna 101 Basics 2010 Advance Train the Trainer Starts @ 0800

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  1. Antenna 101 Basics2010 Advance Train the TrainerStarts @ 0800 Confidential RSI Corporation

  2. A fairly small amount of information and educational material can go a long way toward preventing unnecessary alarm or concern to workers and others. • Consider making some basic educational material available to anyone who wants it, not just those who need it. Confidential RSI Corporation

  3. MPE MathAdvance Train the Trainer Confidential RSI Corporation

  4. First things first… Is RF Radiation a technical issue or a Safety issue? You can calculate the length of the snake, and how far to stay away, but if it bites you, it bites you! It is a Safety issue! Confidential RSI Corporation

  5. Confidential RSI Corporation

  6. More Information,We added last night after Train The Trainer! DB what is it???? Radio waves Confidential RSI Corporation

  7. STANDARDS FOR ANTENNA GAIN AND LOSS MEASUREMENTS INCLUDE:dB The universal unit of measure, named after Alexander Graham Bell. The dB is a Decibel or 1/10 of one bell. Mathematically, if can be expressed in many ways, • Watts: Output power or magnitude - using voltage, current and resistance as parameters. Volts X Amp =W • dBi: Gain with reference to the Isotropic Radiator. A very popular reference in Wi-Fi antenna systems and other applications using the 802.11 standard. • dBd: Gain reference to a dipole about 2 db • dBm The ratio of two powers referenced to 1mw (0.001Watt). Confidential RSI Corporation

  8. MPE Math Radio waves travel at the speed of light 186,000 miles per second = 300,000 kilometers per second λ TX  wavelength One Hertz equals one full cycle per second Confidential RSI Corporation

  9. MPE Math • meters = centimeters * .01 • meters = inches * .0254 • meters = feet * .3048 • centimeters = meters * 100 • feet = meters * 3.28 • inches = meters * 39.37 • millimeters = meters * 1000 uW = mW * 1000 mW = uW * .001 EIRP = ERP x 1.64 dBi = dBd + 2 or dB + 2 W/m2 = 10(mW/cm2) mW/cm2 = W/m2 10 Confidential RSI Corporation

  10. MPE Math • Wavelength from Frequency • λ = wavelength • f = frequency (in MHz) • Problem 1: Find wavelength of 450 MHz • 30000 = 66.66 cm = 2.19 ft • 450 Industry standard for half wave dipole in ft. λ = 492 MHz RSI Corporation

  11. MPE Math • Frequency from Wavelength • Problem 2: Find frequency (resonance) of someone 6 ft tall. • 6 ft = 182.9 cm • f = 30000 = 164 MHz • 182.9 Resonance λ = 164 λ = 82 MHz Isolated = 41 MHz Grounded RSI Corporation

  12. Gain is real Note: See FCC OET 65 for aperture (dish) antenna equations Estimate of power from gain can be achieved by the following method: The power doubles for every 3 dB of gain 0 dB = 5 Watts 18 dB = 320 Watts 3 dB = 10 Watts 21 dB = 640 Watts 6 dB = 20 Watts 24 dB = 1280 Watts 9 dB = 40 Watts 27 dB = 2560 Watts 12 dB = 80 Watts 30 dB = 5120 Watts 15 dB = 160 Watts So 5 watts into a MW antenna with 30 dB gain would Eventually become 5120 Watts in the far field of the antenna RSI Corporation

  13. Student Exercise ANTENNA GAIN RSI Corporation

  14. Student Exercise Worked Example: • Gain (dB) = 7.5 +20log(6) + 20log(6.5)Gain (dB) = 7.5 +20(0.7781) + 20(0.8129) = Gain (dB) = 7.5 +15.56 + 16.25Gain (dB) = 39.31 TO MUCH MATH, for most!!! Confidential RSI Corporation

  15. Confidential RSI Corporation

  16. MPE Math Radio wave continues to increase in power density over distance with gain ant. Radio wave decreases in power density over distance Far field Near field 4 Bay antenna (6 dBd gain) @ 162 MHz WX Radio & 1000 watts into the antenna = 4000 watts Max Gain

  17. MPE Math • FCC OET 65 Power Density Calculations • Far field only without ground reflections • S=power density in appropriate units (i.e. mW/cm2) • P=power input to antenna in mW • G= numeric power gain of antenna in direction of interest • R (or D)= distance to the center of radiation of antenna • Frii’s Equation • S= PG_ • 4R2 Confidential RSI Corporation

  18. More Field Strength • Ground reflections can double the field strength and cause a four-fold increase in power density. For low mounted antennas on rooftops reflections must be included, take 4 out of the denominator • S= PG/ R2 RSI Corporation

  19. From the “BMP Class” Double the field strength will cause a four-fold increase in power density (MPE). From the ½ day BPM Class RSI Corporation

  20. Gain is real RF power doubles for every 3 dB of gain Every time the field strength doubles there is a four fold increase in power density (MPE) From your ½ day BMP book

  21. CONFIDENTIAL R.S.I. CORPORATION Frequency and Wavelength Frequency in kHz: (300,000) / wavelength in meters. Frequency in MHz: (300) / wavelength in meters. Frequency in MHz: (984) / wavelength in feet. Wavelength in meters: (300,000) / frequency in kHz. Wavelength in meters: (300) / frequency in MHz. Wavelength in feet: (984) / frequency in MHz.

  22. MPE Math • Numeric Gain vs Logarithmic Power Gain • G = 10 • Example: • dBi = dBd +2 • 3db = 5dBi • G = 10 G = 10.5 = 3.16 Gain • Unity = 2 dBi = 1.58 Gain • 3 dB = 5 dBi = 3.16 Gain • 12 dB = 14 dBi = 25.12 Gain dBi 10 5 10 Confidential RSI Corporation

  23. FCC Rulemaking mW/cm2 MPE LAW 100 Controlled 100% 6 Min TWA 5 Check Both E&H < 300MHz 20ontrolled reading is OSHA’S ACTION LIMIT OSHA ACTION LIMIT 1 Uncontrolled .2 30Min TWA 2.4 wireless FM AM Radio Cell phones MW PCS 0.3 1 3 10 30 100 300 1 3 10 30 100 MHz GHz

  24. MPE Math • Power Density Calculations • Far field only without ground reflections • For this example, 150 MHz, 100W with 6 • dB gain antenna, 20 feet (609.6 cm) • away from adjacent tower. • 6 dB must be changed to numerical gain • 100 W = 100,000 mW • Numeric Gain, G= 10^dBi = 10 .8 = 6.3 Gain • 10 • S= PG_ = 100,000 * 6.3 = 630,000 = 630,000 • 4 R2 4 R2 12.57(371612) 4,671,165 • =0.135 mW/cm2 .135/ .2=67.5% The uncontrolled limit for 150 MHz is 0.2 mW/cm2, so NO PROBLEM!! Confidential RSI Corporation

  25. MPE Math • Power Density Calculations • Far field only with ground reflections • For this example, 150 MHz, 100W with 6 • dB gain antenna, 20 feet (609.6 cm) • away on rooftop level. • Numeric Gain, G= 10^dBi = 10 .8 = 6.3 Gain • 10 • S= PG_ = 100,000 * 6.3 = 630,000 = 630,000 • R2 R2 3.14(371612) 1,166,862 • =0.54 mW/cm2 .54/ .2=270% The uncontrolled limit for 150 MHz is 0.2 mW/cm2, so it is a PROBLEM!! Confidential RSI Corporation

  26. Vehicle-mounted antennas from the FCC RFR Web page May 2010 • Vehicle-mounted antennas used for wireless communications normally operate at a power level of three watts or less. These wireless antennas are typically mounted on the roof, trunk, or rear window of a car or truck. Confidential RSI Corporation

  27. FCC Results of Studies may 2010 • Show that, in order to be exposed to RF levels that approach the safety limits it would be necessary to remain very close to a vehicle-mounted wireless antenna for a significant amount of time. The metal body of the vehicle can effectively shield occupants. • Proper installation of a vehicle-mounted antenna to maximize this shielding effect is a good way to minimize exposure. The antennas should be installed either in the center of the roof or center of the trunk of a vehicle. Confidential RSI Corporation

  28. Antenna 101 In order to work safely in an RF environment, it is a good idea to know what frequencies you are exposed to, as the MPE limits are based on frequency and the relationship of the wavelength to the body or its parts. Confidential RSI Corporation

  29. CONFIDENTIAL R.S.I. CORPORATION The Higher the Frequency the Shorter the Wave

  30. Antennas 101 Vertical Antenna (paging, etc.) Cellular or PCS Antenna Groundplane Antenna Confidential RSI Corporation

  31. Antennas 101 Cellular Antenna Microwave Parabolic Antenna General Rule: Cellular/LTE 700-900 MHz, PCS 1.9-2.4 GHz Confidential RSI Corporation

  32. BELOW 20% MPE

  33. THE 1stPANEL ANTENNA!

  34. Antennas 101 Circularly Polarized Dipole Antenna Satellite Receive Dish Circularly Polarized BC Antenna Confidential RSI Corporation

  35. CONFIDENTIAL R.S.I. CORPORATION Length of an Antenna • Quarter-wave antenna: • Length in feet = 234 / frequency in MHz. • Half-wave antenna: • Length in feet = 468 / frequency in MHz.

  36. Antennas 101 Antennas vary greatly: this is a rough guide to ID-ing frequencies Frequency Ranges Approx. Full Element Approx. Length from Length (1/2 wave) Center (1/4 wave) Low Band 30-54MHz 9-16.0 ft. 4.5-8.0 ft. VHF 140-174 MHz 3 ft. 1.5 ft. UHF 400-512 MHz 1 ft. 6 in. 900 MHz 6 in. 3 in. Confidential RSI Corporation

  37. Antennas 101 For Verticals w/ reflectors, Note the length of the reflecting element Length (1/2 wave) Center (1/4 wave) Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft. VHF 3 ft. 1.5 ft. UHF 1 ft. 6 in. 900 MHz 6 in. 3 in. Confidential RSI Corporation

  38. Antennas 101 VHF ½ wave ¼ wave Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft. VHF 3 ft. 1.5 ft. UHF 1 ft. 6 in. 900 MHz 6 in. 3 in. Confidential RSI Corporation

  39. Antennas 101 UHF ½ wave ¼ wave Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft. VHF 3 ft. 1.5 ft. UHF 1 ft. 6 in. 900 MHz 6 in. 3 in. Confidential RSI Corporation

  40. Antennas 101 900 MHz ½ wave ¼ wave Low Band VHF 9.0-16.0 ft. 4.5-8.0 ft. VHF 3 ft. 1.5 ft. UHF 1 ft. 6 in. 900 MHz 6 in. 3 in. Confidential RSI Corporation

  41. VHF (30-300 MHz) Body Wavelength 9 to 1 ½ feet! 30 MHz • At frequencies between 30 and 300 MHz, the human body’s characteristics lend themselves to being a good antenna, where: • The body and its parts experience maximum absorption and therefore acts like an antenna, resonating with the frequency. • The Specific Absorption Rate influences the body’s ability to cool after exposure. • The absorption rate decreases rapidly at frequencies above 300 MHz. 300 MHz 300 MHz CONFIDENTIAL R.S.I. CORPORATION

  42. ANTENNA 101 Offset folded dipole

  43. Antennas 101 Folded Dipole Confidential RSI Corporation

  44. Confidential RSI Corporation

  45. Antennas 101 Yagi Antenna 450MHz General Rule: 6MHz VHF to 2.4GHz Frequency Range Confidential RSI Corporation

  46. 6-30MHz Confidential RSI Corporation

  47. Confidential RSI Corporation

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