SeeedStudio SARK-110, User Manual, Page: 79 / 103

SARK-110 User’s Manual
Rev 1.2.19 January 12
th
, 2020 - 79 - © Melchor Varela
– EA4FRB 2011-2020
After some seconds the results are
shown on the screen.
A screenshot can be captured by
selecting [●]
Note: Try to keep the electrical length of the line exactly the same between the open
and short termination conditions. Ideally you would terminate the line with the same
standard loads that were used to do the Open Short Load (OSL) calibration.
Z0 is obtained by calculating the arithmetic mean of the real part of the following equation for all
the frequency points:
Zsc Zoc Z
 =
0
The calculation of the Velocity Factor (VF) and matched loss is more convoluted and will not be
explained here. The relevant information is that the VF is provided at the upper frequency and
the matched loss is provided at the maximum frequency and the arithmetic mean for all
frequency points.
4.3 Tuning Stubs
The SARK-110 facilitates making ¼-

, ½ -

and other coaxial stubs with the help of Markers
Info feature. Markers Info dialog box provides information about the electrical length of the line.
Let’s illustrate the tuning procedure with an example. In this case we are going to make a ¼-

stub with a RG-58 cable for a frequency of 20 MHz.
Select «SETUP» «Stubs» and specify the fraction of wavelengths (wavelength=0.25) and the
cable velocity factor (VF=0.66).