Connect802 is a nationwide wireless data equipment reseller providing system design consulting, equipment configuration, and installation services.


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An On-Line Path Loss and Link Budget Calculator
for Wireless Network Design Suitability Analysis

Overview and Explanations

NOTE: Results may be subject to arithmetic rounding errors. This calculator is designed to provide results with a level of precision that is sufficient for use in wireless network design. Calculated values represent the arbitrary arithmetic results of standard path loss, Fresnel zone, earth curvature, and link budget formulas. Measurements made in the field may vary from those calculated here since manufacturing tolerances and measurement accuracy introduce variability. Attenuation in cable connectors may vary substantially from theoretical values if oxidation is present. While every effort has been made to assure the accuracy of the calculations, Connect802 makes no guarantee of the accuracy or suitability of this information.

THE FOLLOWING EXPLANATIONS AND TECHNICAL NOTES
ARE PROVIDED TO HELP YOU MAKE THE BEST USE OF THE
CONNECT802 WIRELESS NETWORK PATH LINK BUDGET
AND ANTENNA CALCULATOR


FREQUENCY   BACK TO TOP OF PAGE
Frequency Application Wavelength (Meters) Wavelength (Feet) Number of Wavelengths
for 1-foot
Penetration
800 MHz Cell Phone Communication 0.37 1.25 0.81
2.4 GHz 802.11b/g 0.12 0.41 2.43
5.8 GHz 802.11a and WiMAX 0.05 0.17 5.88
45 GHz Point-to-Point Microwave 0.007 0.02 45.66

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DISTANCE BETWEEN TOWERS   BACK TO TOP OF PAGE

dBLoss = 96.6 + 20 Log10 (distance in miles) + 20 Log10 (frequency in GHz)

TOWER HEIGHT   BACK TO TOP OF PAGE
Background and Technical Perspective:
Earth curvature and the
Visual Line-of-Sight

The difference between VLOS and ground distance is relatively small in most practical situations. Even a 10-foot (3-meter) tall tower has roughly a 4-mile (6 km) VLOS. That's a difference of much less than 10 feet over 20,000+ feet (3 m over 6 km). Because of this relationship (between tower height and the relatively huge VLOS distances achieved from even a small tower) the ground distance is never considered in field design and measurement. On the other hand, Radio Line-of-Sight differs significantly from VLOS and must be considered.
DISTANCE TO OBSTRUCTION
and OBSTRUCTION HEIGHT
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Diagram Depicting Various Antenna System Designer Values
It is well known that the earth bulges slightly at the equator and is slightly elongated at the poles. The planet is not a geometric sphere but, rather, an ellipsoid. Consequently, a great circle path, covering some predetermined number of degrees of arc, will be longer in some directions than in others. A distance measured on a great circle is called a geodetic line. The United States Department of Defense has adopted a reference system that is considered the best fit for the whole earth. This reference system is called the World Geodetic System, and the most recent base measurements were made a standard in 1984, giving rise to the WGS84 standard.

CABLE LOSS   BACK TO TOP OF PAGE
RADIO TRANSMITTER OUTPUT POWER   BACK TO TOP OF PAGE
RECEIVER SENSITIVITY   BACK TO TOP OF PAGE
  Cisco -85 dBm
  Orinoco -82 dBm
  Belkin -78 dBm
  SMC -89 dBm
  Compaq -82 dBm
  ZyXEL -85 dBm
  Netgear -84 dBm
  Zcom -83 dBm
  D-Link -84 dBm
  Demarc -91 dBm
ANTENNA GAIN   BACK TO TOP OF PAGE
REFRACTIVE INDEX   BACK TO TOP OF PAGE
  • Surveyors often use K=6/3 and this results in what is commonly called the "Visual Line-of-Sight"

Background and Technical Perspective:
When performing computations or analyzing data related to spatial relationships it's necessary to understand the differences in measurements for distances on the earth's surface. Data obtained from, or applied to, the real earth (surrounded by a real atmosphere) typically differs from that which would be obtained based on the assumption of a spherical earth and derived using Euclidean or planar metrics. The geometric calculations that could be performed are based on distances being assumed to be a length of an arc of a great circle on a sphere. This geometric result is called a geodetic line, and it is the distance between two points (an antenna and the horizon, for example) that would be experienced by a person walking along a road between the two points. On the other hand, the changes in atmospheric density caused by altitude (density decreases as altitude increases), temperature (hot air is less dense than colder air), and water vapor (moist air is less dense than dry air.. a fact that may seem 'backwards' but it's true.)

     
How far can it "see"? If you were at an elevation such that the geodetic line to the horizon were exactly 10 miles then (using the refractive index of dry air, K=6/5) you would see the horizon 12 miles away (6/5*10=12). Using K=4/3 (typical for RF design) the "Radio Line-of-Sight" (also called the "Radar Line-of-Sight") would be 13.3 miles away (4/3*10=13.33).
EARTH BULGE   BACK TO TOP OF PAGE
This value is calculated based on the distances involved.

Background and Technical Perspective:
Refer to the Refractive Index discussion (above) to understand how the curvature of the earth appears greater than the physical, geometric spherical representation that might be used to calculate line-of-sight to the horizon based on a tangent line from a point at some height above the surface.

RAIN FADE MARGIN   BACK TO TOP OF PAGE
Background and Technical Perspective:
Connect802's projects in Malaysia required careful assessment of Rain Fade for microwave links through the dense rainforests.

TERRAIN ROUGHNESS   BACK TO TOP OF PAGE
Calculator Pull-Down Option Examples of Terrain
Generally flat terrain surface Open parklands (use Foliage Attenuation if the link must pass through trees), farm land, water, airports (across the runway environment), thick jungle-like vegetation (where the link will pass over the consistent-height tree tops)
Suburban area; buildings roughly the same height Housing developments, smaller town downtown area (generally rural communities), apartment complexes (when the link passes over the top of the complex), industrial parks (with similar-height warehouses and offices) ALSO gently rolling hills
Urban area; buildings of different heights City downtown areas with many different building heights, large university campus environments (where the link passes over the campus) ALSO mountain areas with steep, undulating topography
Ignore terrain roughness This option tells the calculator not to add any attenuation factor for terrain roughness
LINK FADE MARGIN   BACK TO TOP OF PAGE
ANTENNA MAXIMUM LINEAR DIMENSION BACK TO TOP OF PAGE
2.4 GHz Yagi Antenna
Grid Parabolic Antenna
NOTE: Results may be subject to arithmetic rounding errors. This calculator is designed to provide results with a level of precision that is sufficient for use in wireless network design. Calculated values represent the arbitrary arithmetic results of standard path loss, Fresnel zone, earth curvature, and link budget formulas. Measurements made in the field may vary from those calculated here since manufacturing tolerances and measurement accuracy introduce variability. Attenuation in cable connectors may vary substantially from theoretical values if oxidation is present. While every effort has been made to assure the accuracy of the calculations, Connect802 makes no guarantee of the accuracy or suitability of this information.