TAP™ software allows elevation values to be corrected for earth curvature, including atmospheric diffraction effects. The formula used for elevation correction is: Ecorr = E + (78.5/k) x 10-3 x D x (P-D) Ecorr is the corrected elevation in meters. E is the actual elevation in meters. k is the curvature correction factor to compensate […]

The reliability of the system generally can be improved by the use of a second receiving antenna located at a different height (“space diversity”). Both antennas (primary and diversity) feed the receiver through appropriate switching devices. The space diversity improvement factor for vertically separated receive antennas is computed as: I = (7 x 10-5 x […]

The reliability of a system based on the computed fade margin is calculated based on the following equation (from Lenkurt) Undp = a x b x 2.5 x 10-6 x f x D3 x 10-F/10 where: Undp is the non-diversity outage probability. a is the terrain factor. b is the climate factor. f is the […]

The following applies to the legacy microwave link reliability predictions.  Frequency diversity is not calculated for the Two-Way Microwave link reliability predictions. The TAP fixed facility database includes a field for frequency diversity. If frequency diversity is not employed, set the “Diversity Frequency” field to zero (0). If frequency diversity is used, enter the second […]

The TAP fixed facility database includes fields for digital fade margin values. These values can be used in addition to the computed thermal fade margin to compute a composite fade margin value.  Note that the composite fade margin is used in the legacy microwave link reliability predictions.  The two-way microwave link reliability predictions use the […]

The climate factor used in the reliability calculation can be entered directly or computed from average annual temperature information. Lenkurt suggests the following values: .5 for gulf coast or similar hot, humid areas. .25 for normal interior temperate or northern areas. .125 for mountainous or very dry areas. In the legacy microwave reliability calculation, the […]

The terrain and humidity factor used in the microwave reliability calculation can be entered directly, or the value can be computed from humidity and terrain roughness information. Lenkurt (1970) suggests the following values: 4 for very smooth terrain, including over water. 1 for average terrain, with some roughness. .25 for mountainous, very rough, or very […]

Atmospheric Absorption The loss from atmospheric absorption can be entered directly or computed by pressing the “Calculate Loss” button for the Absorption Loss field. Absorption loss is computed as a function of the frequency using the complete length of the path. The loss value is determined from curves based on van Vleck (1947), providing separate […]

Several types of calculations are used to make microwave link reliability predictions. One of these is the microwave path free space loss. The free space loss is computed based on the path length and frequency using the equation: A = 96.6 + 20 LOG(F) + 20 LOG(D) where: A is the attenuation in dB. F […]

There is a great deal of confusion when engineers, technicians, and equipment salespersons talk about units of antenna gain and field strength. This FAQ discusses units of gain and field intensity and explains how to convert between some of these units when appropriate. Units of Antenna Gain While field strength at any location is independent […]