SteppIR SARK-110 User manual

This document is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
© Melchor Varela – EA4FRB 2011-2014
SARK-110
Vector Impedance Antenna Analyzer
User’s Manual
Revision 1.1.7

SteppIR SARK-110 User’s Manual
Rev 1.1.7 October 29th, 2014 - 2 - © Melchor Varela – EA4FRB 2011-2014
Updated to Firmware Version 0.8.x

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Contents
1INTRODUCTION ....................................................................................................................... 5
2MAIN FEATURES ..................................................................................................................... 6
3OVERVIEW OF FUNCTIONS ................................................................................................... 7
4OPERATING THE STEPPIR SARK-110 .................................................................................. 8
4.1 SCREEN LAYOUT .................................................................................................................. 8
4.2 STATUS SYMBOLS MEANING ............................................................................................... 10
4.3 MEANS OF INPUT ................................................................................................................ 10
4.4 CHANGING THE FREQUENCY ............................................................................................... 11
4.5 CHANGING THE SPAN ......................................................................................................... 12
4.6 FREQUENCY PRESETS ........................................................................................................ 13
4.7 USING MARKERS ................................................................................................................ 13
4.8 CHANGING THE VERTICAL AXIS PARAMETER ........................................................................ 16
4.9 SAVING AND RECALLING MEASUREMENTS ........................................................................... 17
4.10 TAKING SCREENSHOTS ................................................................................................... 20
4.11 CHANGING THE OPERATING MODE .................................................................................. 20
4.12 CHANGING THE SETTINGS ............................................................................................... 21
5SCALAR CHART MODE ........................................................................................................ 32
6SMITH CHART MODE ............................................................................................................ 34
7SINGLE FREQUENCY MODE ............................................................................................... 36
8CABLE TEST MODE (TDR) ................................................................................................... 38
9FIELD MODE .......................................................................................................................... 42
10 MULTI-BAND MODE .......................................................................................................... 44
11 SIGNAL GENERATOR MODE ........................................................................................... 46

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12 COMPUTER CONTROL MODE ......................................................................................... 51
13 TRANSMISSION LINE ADD/SUBTRACT .......................................................................... 53
14 SPECIFICATIONS ............................................................................................................... 56
15 PRECAUTIONS ................................................................................................................... 60
16 REGULATORY WARNING ................................................................................................. 60
17 ACKNOWLEDGMENTS ..................................................................................................... 61
APPENDIX A: THEORY OF OPERATION .............................................................................. 62
APPENDIX B: FUNDAMENTAL PARAMETERS .................................................................... 65
APPENDIX C: UPGRADING THE FIRMWARE ...................................................................... 67
APPENDIX D: OSL CALIBRATION ........................................................................................ 68
APPENDIX E: FREQUENCY CALIBRATION ......................................................................... 71
APPENDIX F: DETECTOR CALIBRATION ............................................................................ 72
APPENDIX G: FREQUENCY PRESETS FILE ........................................................................ 75
APPENDIX H: SCALE PRESETS ........................................................................................... 76
APPENDIX I: CUSTOM CABLE SETTINGS ............................................................................. 78

SteppIR SARK-110 User’s Manual
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1 Introduction
The SteppIR SARK-110 Antenna Analyzer is a pocket size instrument providing fast and accurate
measurement of the vector impedance, VSWR, vector reflection coefficient, return loss, and R-L-C
(as series or parallel equivalent circuits). Additionally, the analyzer features a TDR (Time Domain
Reflectometer) mode which is intended for fault location and length determination in coaxial cables
as well as a programmable RF signal generator.
The SteppIR SARK-110 is intended for standalone operation but also operates connected to a
personal computer in combination with the SteppIR SARK Plots client software for Windows, further
enhancing the capabilities of the instrument.
Typical applications include checking and tuning antennas, impedance matching, component
testing, cable fault location, measuring coaxial cable losses and cutting coaxial cables to precise
electrical lengths. As a signal generator it is ideal for receiver calibration, sensitivity tests,and signal
tracing.
The SteppIR SARK-110 features a Direct Digital Synthesis (DDS) generator with a range of 0.1 to
230 MHz and a frequency resolution of 1 Hz. The instrument has full vector measurement capability
and accurately resolves the resistive, capacitive and inductive components of a load. The
measurement reference plane is automatically adjusted via the Open/Short/Load calibration
standard for higher measurement accuracy. Also, the analyzer implements a transmission line
addition or subtraction feature in order to make antenna measurements while discounting the effect
of the feed line.
The user interface, based on a color display, has been designed to be intuitive and easy to use. The
graphical impedance displays provide a quick view of the antenna impedance characteristics on a
user-selected sweep range. This includes the graphical plot of two user-selectable parameters in a
scalar chart or the complex reflection coefficient in Smith chart form. To help speed up
measurements, two markers are available, both of which are user positionable or can operate in
automatic tracking mode.
The Multiband mode is a unique feature of the SteppIR SARK-110 whereby it is able to display
simultaneously the plot of an impedance parameter in four scalar charts. This feature is ideal for
tuning multiband antennas.
Also included is a single frequency measurement mode which presents a complete impedance
parameter analysis at a user selectable frequency and displays diagrams of equivalent circuits.
The analyzer uses an internal 2MB flash disk for the storage and recall of measured parameters,
screenshots, analyzer configuration and firmware updates. This disk is accessible via USB so the

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measured parameters can be downloaded to a PC for analysis using the ZPLOTS spreadsheet
program or with SteppIR SARK Plots client software for Windows.
Please let us have your suggestions through the website http://www.sark110.com as we are highly
motivated to extend this device’s functionality based on community requests.
2 Main Features
 Pocket size and lightweight
 Solid aluminum case
 Intuitive and easy to use
 Operating modes: Scalar Chart, Smith Chart, Single Frequency, Cable Test (TDR), Field
Mode, Multi-band, Signal Generator, and Computer Control
 Good accuracy over a broad range of impedances
 Resolves the sign of the impedance
 Manual and automatic positioning tracking markers
 Internal 2MB USB disk for the storage of measurements, screenshots, configuration and
firmware upgrade
 Exports data in ZPLOTS-compatible format for further analysis on a PC
 SARK Plots client software for Windows
 Lifetime free firmware upgrades
 Open to community requested features
 Open source Software Development Kit (SDK) including a device simulator for development
of user applications

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3 Overview of Functions
Power Switch
Mini USB Port
Navigator A
Navigator B
Run/Hold
Select
Save Screen
Save Conf.
Test Port
3" TFT LCD
SARK-110
é••• ê
-•••+
Ø||
USB
ON
Test
Port
The unit has a Test Port located on the left side to connect to the device under test. This receptacle
accepts straight MCX plug connector types. The product pack includes a MCX plug to BNC female
cable adapter.
The USB port located on the right side allows connecting the unit to a personal computer for
communication and internal battery charging using a compatible mini-USB cable (not included). The
unit charges the internal battery when connected to USB. The internal battery charger manages
automatically the charge cycle and stops the process when battery is fully charged. The complete
charge cycle takes around 3.5 hours.
Slide the Power Switch button located on the right side to the ON position for turning on the unit. An
automatic power-off feature can be set for power-saving after a user specified period of inactivity.
Operation is controlled by four buttons and two navigation keys located on the top side of the unit. A
3” TFT color LCD is used for display diagrams.

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4 Operating the SteppIR SARK-110
This chapter provides information about the SteppIR SARK-110’s basic functionality and user
interface.
4.1 Screen Layout
The following figure shows the screen layout in Scalar Chart mode. It shows diagram areas that are
the same for all operating modes of the SteppIR SARK-110. Screen layouts that show specifics for
each operating mode are provided in corresponding sections of this manual.
1
Diagram
11
Markers information
2
Traces
12
Detailed measurements
3
Markers
13
Frequency and span settings
4
Vertical axis labeling
14
Transmission Line length setting
5
Horizontal axis labeling
15
Reference impedance setting
6
Main menu
16
Loaded data file name
7
Highlighted menu option
17
Disk write operation in progress
8
Submenu
18
Calibration status

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9
Highlighted submenu option
19
Run/Hold status
10
Currently selected submenu option
20
USB/Battery status

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4.2 Status Symbols Meaning
Calibration status
Calibrated
Non-calibrated
Run/Hold status
Measurements in progress
Measurements on hold
USB/Battery status
Device operating from USB
Charge status of the battery when the device is operating from the
battery
Disk
Disk write operation in progress
4.3 Means of Input
There are four buttons and two navigation keys on the SteppIR SARK-110.
Navigator A
Navigator B
Run/Hold
Select
Save Screen
Save Conf.
é••• ê
-•••+
Ø||
SARK-110
Navigator A
Navigator A is used to navigate within the main menu (left side of the screen). The active option is
highlighted with a green background color.
Navigator B
Navigator B is used for changing the value of the highlighted option in the main menu (for Freq,
Span, Marker1, Marker2, LeftY and RightY) and to navigate within the popup submenus.
Run/Hold [►||]

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The Run/Hold button is used to control the operating state of the SteppIR SARK-110: Working or
Paused. In the paused state the signal generator and measurement circuits are inactive.
Ø Note: when loading a stored data file the analyzer is automatically placed in a paused
state.
Select [■]
The button is used to activate the popup submenu associated with the highlighted option and for
selecting the desired option within the popup submenu.
Ø Note: Pressing any other button will cancel a selection.
Save Screen [●]
The Save Screen button is used to take a screenshot of the current screen. The screenshot is
stored on the internal flash disk.
Save Conf. [▲]
The Save Conf. button is used to store the complete analyzer state and settings. The stored state is
restored automatically after the device is powered on.
4.4 Changing the Frequency
There are two methods of editing the frequency (centre frequency for sweep modes):
(i) Use Navigator A to highlight «Freq» in the main menu on the left side of the display. Press the
Select [■] button to display the popup dialog associated with «Freq». Then use Navigator B to
change the frequency. The frequency will change according to the current frequency multiplier that is
highlighted in reverse video. Use Navigator A to change the frequency multiplier position if needed.
Press the Select [■] button to validate the frequency selection. Press any other button to cancel the
operation.
The screenshot below is of the frequency edit dialog, showing the highlighted frequency multiplier
positioned over digit 5 (frequency increments of 10 KHz).

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(ii) Use Navigator A to highlight «Freq» in the main menu on the left side of the display. Then use
Navigator B to change the frequency. The frequency will change according to the current frequency
multiplier. The frequency multiplier can be changed from the popup dialog, see (i) above.
Ø Note: the span range will be adjusted automatically if the resultant upper or lower
frequency entry causes it to fall outside operational limits.
4.5 Changing the Span
There are two methods of editing the Span:
(i) Use Navigator A to highlight «Span» in the main menu on the left side of the display. Press the
Select [■] button to display the popup dialog associated with «Span». Then use Navigator B to
change the span. The span will change according to the current span frequency multiplier that is
highlighted in reverse video. Use Navigator A to change the span frequency multiplier position if
needed. Press the Select [■] button to validate the span selection. Press any other button to cancel
the operation.
The screenshot below is of the span edit dialog, showing the span frequency multiplier positioned
over digit 7 (frequency increments of 1 MHz).

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(ii) Use Navigator A to highlight «Span» in the main menu on the left side of the display. Then use
Navigator B to change the span. The span will change according to the current span frequency
multiplier. The span frequency multiplier can be changed from the popup dialog, see (i) above.
4.6 Frequency Presets
The analyzer provides predetermined frequency and span settings including the amateur radio
bands and other suitable settings. Use Navigator A to highlight «Preset» in the main menu.
Press the Select [■] button to activate the Preset popup submenu. Use Navigator B to highlight the
desired preset. Press the Select [■] button to validate the preset selection. Press any other button
to cancel the operation.
See in the screenshot below the available presets:
4.7 Using Markers
The SteppIR SARK-110 has two markers that can either be manually positioned by the user or set
to operate in automatic tracking mode. The markers indicate the horizontal and vertical position of

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the point they are positioned on. The horizontal position of a marker is shown by a dotted vertical
line which extends from the top to the bottom of the measurement diagram. The markers
information window, in blue background, shows the frequency or distance (in cable test mode) and
the two values that correspond to the plotted values at each of the markers.
Use Navigator A to highlight either «Marker1» or «Marker2» in the main menu.
Press the Select [■] button to activate the Marker popup submenu. Available options are: «Enable»
for activating or deactivating the marker, «Select» for selecting or deselecting the marker, and
«Tracking» for selecting the tracking mode; see screenshot below:
The «Select» option activates or deactivates the display of detailed parameters at the marker
position. The screenshot below shows Marker1 in the selected state:
The automatic tracking feature makes positioning of the markers easier, thus helping the user to
speed up measurements.
The following tracking modes are available:

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 Peak Min (p)
 Peak Max (P)
 Absolute Min (m)
 Absolute Max (M)
 Value Cross Any (X)
 Value Cross Up (^)
 Value Cross Down (v)
The automatic positioning of markers is activated in the «Tracking» sub-option. Select the tracking
mode from any of the modes above and then the applicable parameter to track. In addition, a
detection value must be specified for the Cross detection modes.
For example, you could set Marker 1 to track automatically the minimum VSWR values in the trace:
«Marker1» «Tracking» «Peak Min» «VSWR»; and Marker 2 to track the crossovers on the 50-ohm
impedance value: «Marker2» «Tracking» «Cross Any» «Z» «50.0».
You could also program the unit to detect the bandwidth by setting «Marker1» «Tracking» «Cross
Down» «VSWR» «2.0»; and «Marker2» «Tracking» «Cross Up» «VSWR» «2.0».
Navigator B will be used to move to the different detection points, except for the Max and Min
tracking modes where logically there is only a single detection point.
The tracking mode for each marker is shown in the markers information window. This information is
displayed in red if either the data is not available or if the tracking condition cannot be resolved;
otherwise it is displayed in green.
The screenshot below shows Marker1 tracking the minimum value of VSWR and Marker 2, tracking
all |Z| crossing at 50-ohms:

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4.8 Changing the Vertical Axis Parameter
In Scalar Chart mode, the SteppIR SARK-110 can display two traces from any of the available
parameters for the vertical axis. Use Navigator A to highlight either «LeftY» or «RightY» in the main
menu.
There are two methods of changing the selected vertical axis parameter:
(i) Press the Select [■] button to activate the LeftY or RightY popup submenu. Use Navigator B to
highlight the desired submenu parameter option. Press the Select [■] button to validate the
selection. Press any other button to cancel the operation.
The screenshot below show the available parameters for the vertical axis:
(ii) Use Navigator B when either the «LeftY» or «RightY» option is highlighted. Options are
selected sequentially.

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4.9 Saving and Recalling Measurements
The SteppIR SARK-110 has the capability to store measurements to the internal disk and recall
them either to review the data later in the analyzer screen or to download the data from the USB
disk to a PC for further analysis using SARK Plots or the ZPLOTS Excel application, available from
http://www.ac6la.com/zplots.html.
Use Navigator A to highlight «File» in the main menu for data file operations.
Press the Select [■] button to activate the File popup submenu. Use Navigator B to highlight the
desired submenu File option.
«Save Data File»
The Save Data File option allows saving the current measured data for further review:
After selecting the «Save File» submenu option, enter the file name. By default, the file name has
the format “sark_xxx.csv” (or “sark_xxx.tdr” for Cable Test mode), where xxx is an automatically
assigned number. To change the file name, use Navigator B to change the character value and
Navigator A to change the character position highlighted in inverse video. Press the Select [■]
button to validate the selection. Press any other button to cancel the operation.

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«Load Data File»
To retrieve the stored data, select the «Load Data File» submenu option. A second popup submenu
is displayed with a list of available files. Use Navigator B to highlight the desired file. Press the
Select [■] button to validate the selection. Press any other button to cancel the operation. Once the
file is selected, the data is loaded and plotted.
«Load Bitmap File»
Use the «Load Bitmap File» option to display a captured screenshot. Press the Select [■] button to
finalize the operation.

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«Browse Bitmaps»
Select the option «Browse Bitmaps» from the «File» menu to review the captured screenshots. Use
Navigator B to select the different bitmaps. Press the Select [■] button to finalize the operation.
«Delete File»
Use the «Delete file» option to delete a single file on the device disk.
When selecting the «Delete File» option a popup submenu will be displayed with the list of available
files. Use Navigator B to highlight the desired file. Press the Select [■] button to validate the
selection. Press any other button to cancel the operation.
«Delete All»
Use the «Delete All» option to delete all user files.
When selecting the «Delete All» option, a confirmation dialog box is activated to prevent an
accidental deletion.

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4.10 Taking Screenshots
Press the Save Screen [●] button to capture the current screen. Then enter the file name. By default
the file name has the format “sark_xxx.bmp”, where xxx is an automatically assigned number. To
change the file name, use Navigator B to change the character value and Navigator A to change the
character position highlighted in inverse video. Press the Select [■] button to validate the selection.
Press any other button to cancel the operation.
Select the options «Load Bitmap File» or «Browse Bitmaps» from the «File» menu to review the
captured screenshots. Also, they can be reviewed on a PC because they are in Windows bitmap
compatible format.
Ø Note: the bitmap files use a significant amount of disk (188KB per screenshot)
4.11 Changing the Operating Mode
Use Navigator A to highlight «Mode» in the main menu.
Press the Select [■] button to activate the Mode popup submenu; see the screenshot below: