# Transmission lines calculator

This transmission line calculator calculates the impedance at input and attenuation of a given transmission line once terminated with the given load.

All the math involved is well explained and documented by Dan AC6LA on his site. The K values for the various transmission lines are also copied from his Transmission Line Details windows software which I recommend to download and try for much more complete information.

## Input

The information below describes the meaning of the data that can be entered in the program:

• Load R – resistive component of the load (i.e. the antenna)
• Load X – reactive component of the load; this can be positive or negative
• Freq. – required frequency in MHz
• Length unit – select your favorite unit (meters or feet)
• Length – lenght of the transmission line in the unit selected above
• Gen. R – resistive component of the generator (i.e. your radio), usually 50; it will be used to calculate the VSWR seen by it
• Gen. X – reactive component, same as above (usually 0)
• Cable type – type of the cable; select “custom” to insert custom data (see Z0, VF, K0, etc. below)
• Z0, VF, K0, K1 and K2 – line parameters that describe the transmission line; they can be edited only by selecting “custom” cable type

## Output

The information below describes the meaning of the data reported by the calculator:

• Cable type – cable type selected for this calculation
• Length – length of the cable, expressed in the selected measurement unit
• Z at input – impedance of the cable at other end: this is the result of the impedance transformation done by the transmission line
• Generator Z – impedance selected for the generator, usually 50+j0 (it has effects only on “VSWR at gen”)
• VSWR at load – VSWR that the transmission line encounters at load according to its characteristic impedance
• VSWR at gen – VSWR seen by a generator that is designed for “Generator Z” impedance (usually 50+j0)
• True Zo – true characteristic impedance of the transmission line (usually shows a little reactive component)
• Matched loss – loss in dB due to cable attenuation when the load is perfectly matched
• Total loss – true loss in dB accounting also extra loss due to mismatch; if the load is perfectly matched to the line characteristic impedance, it is identical to “Matched loss”