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TWLLC helpOverviewThis calculator is designed to model the common configuration where a transmitter which is designed for a particular load impedance, is connected to a an antenna of that impedance, over transmission line of the same characteristic impedance. The calculator allows specification of the transmission line loss 'upstream' and 'downstream' from the measurement point. It is intended to provide a simple analysis of the system at the transmitter and at the antenna where a directional wattmeter is used to take measurements in the system at some convenient intermediate point. Input values / formatsThe input fields may support flexible input format. In general, the formats supported include traditional floating point number (50.00), scientific notation (5.05E1). Complex numbers must be entered as floating point cartesian format with a leading j on the imaginary part, and no leading, embedded or trailing spaces. The imaginary part is optional if it is zero. For example 5.1j34.2, 43, 1e8. The calculator will not accept zero for an impedance or admittance, use a very small (eg 1e8) or very large (1e8) impedance or admittance as appropriate for open circuit or short circuit. Model variablesConductivityConductivity of the conductor material in S/m. Rel permeabilityRelative permeability of the conductor material. DiameterDiameter of the round conductors. SpacingCentre to centre spacing of the round conductors Velocity factorVelocity factor of the line as described. Twist rateThe number of full twists per meter in a twisted pair. Loss tangentLoss tangent of the dielectric. If the space around and between the conductors is partially filled, use an adjusted value to allow for the partial fill if needed. (Hint: calibrate the model using the adjustment to permittivity above.) LengthLength of transmission line specified as either metres, wavelengths or degrees. The results calculates the electrical length in wavelengths and degrees. FrequencyFrequency in Megahertz. MismatchThe type of mismatch modelled, it may be NONE, Average VSWR, Zload or Zin. Note that specifying a negative value for the real component of impedance, or an impedance for Zin that results in negative Rload will prevent calculation of some results. The calculation of loss using VSWR is an approximation that is reasonably accurate on long lines with low VSWR and low loss. The methods using the impedance of the load or looking into the line produce accurate answers, and are the only way to get reasonably accurate answers with high VSWR or short lines. ZinThe impedance looking into the transmission line from the generator end. ZloadThe impedance terminating the transmission line opposite to the generator end. GAMMAinThe complex reflection coefficient GAMMA at the input, expressed in polar format magnitude<angle (angle in degrees). GAMMA is for the actual Zo as calculated, not nominal Zo. GAMMAloadThe complex reflection coefficient GAMMA at the load, expressed in polar format magnitude<angle (angle in degrees). GAMMA is for the actual Zo as calculated, not nominal Zo. Average VSWRThe average VSWR over the transmission line. TitleA title for results documentation purposes only. CodeCode is the unique key used in the TLLC database for entries. ZoThe characteristic impedance of the transmission line at the modelled frequency. Velocity factorThe velocity factor of the transmission line at the modelled frequency. Line loss (matched)The line loss under matched conditions at the modelled frequency. Line lossThe total line loss under the mismatched conditions at the modelled frequency. EfficiencyThe ratio of real power delivered to the load to the real power into the transmission line at the generator end, expressed as a percentage. ZloadThe complex load impedance. gamma (γ)The complex line propagation constant at the modelled frequency. k1, k2The loss model coefficients. Many other programs use the same type of model for transmission line loss. This calculator displays the values of k1 and k2 based on distance in metres and frequency in Hz. DisclaimerUse at your own risk, not warranted for any purpose. Do not depend on any results without independent verification. 

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