domingo, 19 de mayo de 2013

SARK Plots for SARK-110 preview available

The SARK-110 can be connected to the PC USB port and it is accessible as a mass storage device for functionalities such as for updating the firmware of the device or for the upload of the measurements to the AC6LA ZPlots program for post analysis.

Starting from firmware release v0.7.4 the SARK-110 implements a composite USB device class including the former mass storage class plus a custom USB HID class allowing the remote control of the device. The specification of the HID interface is public and available at Commands Interface (Beta) for anyone wishing to develop its own client software for any of the major OS's.

The SARK Plots is a client application for the SARK-110 for the Windows operating system. This application is aimed to augment the capabilites of the device when a PC is available, for instance when operating it at the shack.

The software is still in development but a preview is available in the SARK Plots section. This preview is functional but there are some program features that are not yet functional and this program has not been extensively tested. The software will be updated periodically so please check for updates.

The SARK Plots provides equivalent features as the available in the device firmware such as Scalar Chart, Polar Chart (similar to the Smith Chart) and the Time Domain Reflectometer mode for cable testing.

The software provides features such as cursor, markers, user defined or automatic ranges, etc. In addition it will be provided advanced features as transmission line measurements, and adding or substracting transmission lines.

The following screenshots show the functionalities of this program:

Scalar Chart


Polar Chart


Time Domain Reflectometer

jueves, 18 de abril de 2013

SARK100 Clones at eBay

Recently I found several SARK-100 clones sold at eBay. The "Mini" units look a nice improvement to the initial hardware design.

Notice that I do not have any link with the manufacturers and sellers and I cannot ensure the performances and provide support for these units.

SARK-110: New firmware release 0.7.4

A new SARK-110 firmware is available in the Firmware area, and includes some enhancements and bug fixes.

One of the most important enhancements is the implementation of a computer control mode through USB custom HID mode, in addition to the existing mass storage functionality. This feature will be used by a client software for Windows PC that it is currently in development.

Besides, the interface specification and basic interface source code, is available at Commands Interface (Beta) to facilitate the integration with client software from third parties.

Regarding the basic measurement features, there are further improvements in the implementation of the OSL calibration algorithm and corrections in the Cable Test Mode, mainly in the presentation of the Step response. In addition, there are some slight changes to the impedance ranges for the Low scale.

It has been added a VSWR audio feedback to the Single Frequency mode. When activated, the analyzer produces beeps of different duration as indication of the VSWR. The audio is produced only for VSWR values between 1.0 and 10.0, and the duration is shorter for the lower values.

Finally there are some enhancements such as new frequency presets, the capability to change the SWR circle in the Smith Chart, and minor changes to the user interface.

The User Manual has been updated for this new firmware release. The new document is available in the Documents area.

domingo, 10 de febrero de 2013

domingo, 6 de enero de 2013

SARK-110: new firmware release 0.7.2

A new release of the SARK-110 firmware and the PC Simulation is available in the Firmware and PC Simulation areas. The changes are described in the Release Notes document.

One important consideration is that from now on, there will be two firmware variants in each release: one limited to 200 Mhz and the other working up to 230 MHz. The reason for this is because migrating to the 230 MHz version requires performing the full calibration process of the unit, therefore it is delivered the 200 MHz variant to upgrade the unit to the new version without the calibration. The firmware files are the following:
Frequency range: 230 MHz.
It is required performing Detector Calibration and OSL calibration when upgrading to this release from versions v0.7.2.a, v0.7.0 or v0.6.5.  Do not upgrade to this version if you don’t have the proper calibration loads
Frequency range: 200 MHz.
No calibration needed when upgrading from versions V0.7.0 or v0.6.5

The implemented changes in this release are improvements in the look and feel of the user interface and the addition of the "Field Mode", intended for field operation, see below some examples:
Field Mode:

Improved menus:
More visible trace in Smith Chart mode:

viernes, 14 de diciembre de 2012

SARK-110: New firmware releases 0.7.1 and 0.7.0

Two new releases of the SARK-110 firmware and the PC Simulation are available in the Firmware and PC Simulation areas. The changes are described below and in the Release Notes document.

The reason for releasing two versions is that the extension of the frequency range of the device requires performing the complete calibration of the instrument and hence you will require the complete set of calibration loads. Therefore if you don't have the complete calibration set or you don't have the need to extend the range to 230 MHz you should update to release v0.7.0.

Version 0.7.1

Release date: December 14th, 2012
  • Extended the frequency upper range to 230 MHz
  • It is required performing Detector Calibration and OSL calibration when upgrading to this release from previous versions. Do not upgrade to this version if you don’t have the proper calibration loads

Version 0.7.0

Release date: December 14th, 2012
  • Reorganized the traces menu and added new traces. The available traces are the following: Rs, Xs, Rp, Xp, |Zs|,
  • Changed the measurement representation in the Detailed Measurements window to a more consistent format, displaying the VSWR, the impedance in rectangular and in polar form, and the reflection coefficient in polar form. Example:
    • Swr:10.09 Z:504.5+j2.1 |Z|=504.6<0 .2=".2" ho="ho" span="span">
  • Added the possibility to disable the traces in the rectangular chart. This option is available in the LeftY and RightY menu.
  • Navigation keys center (push) actuator functional
  • Added a moving average filter for the rectangular and Smith chart diagrams. The filter could be enabled or disabled by accesing to the menu option.
  • Improved the values range limits checking
  • Adjusted slightly the Scale limits presets
  • In Single Frequency mode the inductance or capacitance graph will be shown only if the reactance (X) is higher than 2.0.
  • Improved values range checking when reading ZPlots files
  • Renamed “Antenna Test” in the mode menu by “Rectangular Chart”
  • Renamed “Single” in the mode menu by “Single Frequency”
Bug fixes:
  • The calculated inductance values in the Single Frequency mode were incorrect; the actual value was 1000 times less than the presented value.

© EA4FRB - Melchor Varela 2012, Todos los derechos reservados

jueves, 11 de octubre de 2012

Preorder Now! Pocket Size Antenna Analyzer SARK–110

The SARK-110 is a completely new design concept for an Antenna Analyzer. This is a truly pocket size device so you can take it anywhere. It offers a gorgeous 3” high-resolution, active-matrix color display that allows information-rich diagrams.

Its small size does not mean compromising the features and measurement performances. It has a frequency range from 0.1 to 230 MHz with 1 Hz of resolution. It has full vector measurement capability and accurately resolves the resistive, capacitive and inductive components of a load. The accuracy is good over a broad range of impedances and rivals any of the competitive devices in the market, see comparative. The measurement reference plane is automatic adjusted via the Open/Short/Load calibration standard to enable the accurate impedance measurements at the end of an intermediate coaxial cable.

The SARK-110 allows you to quickly analyze any antenna over a user defined frequency range. In real time, you can see at a glance the resonant frequencies of the antenna, the VSWR, the complex impedance, reflection coefficient, return loss, and R-L-C as series or parallel equivalent circuits. You can test and tune coaxial cables and phasing stubs. You can adjust and test RF matching networks, antenna tuners, and RF amplifiers without applying power. Besides you can measure the impedance of components such as inductors, capacitors, and traps at RF frequencies.

What’s inside this tiny gem? The SARK-110 is controlled by a powerful STM32 MCU with a Cortex M3 core and with plenty of internal memory. In addition there is a 2MB flash memory for data storage. The analyzer uses two frequency sources that are heterodyned to produce a low frequency signal in the audio range that it is amplified filtered and then analyzed using the discrete Fourier transform (DFT). The signal generator is provided by a dual direct digital synthesizer (DDS) which generates the stimulus signal for the impedance measurement and the local oscillator signal for the mixers. There are two independent sensing channels for the measurement of the voltage and current magnitude and phase difference. Both channels run simultaneously and drive two synchronized 12-bit ADC converters, providing a good accuracy for the phase measurement. The block diagram is illustrated in the Figure 1.

Figure 1, Block diagram

The user interface has been designed to be intuitive and easy to use. On screen menus provide user guidance and the operation is mainly controlled by the two navigation keys. The graphical impedance displays provide a quick view of the antenna impedance characteristics on a user selected frequency range. This includes the graphical plot of two user selectable parameters in a rectangular diagram or the complex reflection coefficient in a Smith chart form.

There are two markers that can either be manually positioned by the user or can operate in automatic tracking mode. It is possible to set the markers to track the maximum or minimum values of any measured parameter or to track when the measured parameter arrives to a specified value. This feature is very convenient when tuning an antenna since the markers positions are automatically updated following the changes without the user intervention.

As an example the figures below show the rectangular and Smith Chart plots for a loop antenna for a reader for HF contact-less cards (RFID). The two markers were positioned at the resonant points which are the special interest for this antenna example. The measurements are taken and plotted in real time so you can tune the antenna and see the results immediately. Besides you can quickly change between both diagram representations depending whether representation is more convenient for the analysis.
Figure 2, Rectangular diagram, R and X plot
Figure 3, Rectangular diagram, VSWR and |Z| plot
Figure 4, Smith Chart diagram

The image below shows a screenshot of the ZPlots program presenting the data captured by the SARK-110 from the example loop antenna above. This is really a great tool for the post-analysis of the measured data in the PC and adds some useful features such as add or subtract transmission line parameters.
Figure 5, ZPlots screenshot

The SARK-110 provides as well a single frequency measurement mode which presents the complete impedance parameters at a user selectable frequency. To facilitate the reading, the analyzer displays graphically the R-L-C as both series and parallel equivalent circuit and the SWR as a convenient bar graph. In this mode you can use this device as a stable RF generator for testing and alignment.

Figure 6, Single frequency mode

If you still do not own a SARK-110 you can try the free SARK-110 Demo for PC (Windows) to evaluate the operation of the device without the need of the actual hardware. You can see how easily is to operate and learn about the capacities of the device.

The SARK-110 is as well a hackable device. You can experiment with the device by writing an application using the provided open-source SDK. Besides the SDK includes a device simulator for the PC so you can easily debug your application before loading to the device. For more advanced users, the SARK-110 board provides connections to the STM32 SWD interface so you can use the ST-Link in-circuit debugger or equivalent to program or debug your software.

With its pocket size, features, and simple user interface the SARK-110 offers a perfect device for HF/VHF impedance measurements for the RF experimenter and for the amateur radio operator. Whether you are at home in your shack or in the field during a field day or expedition.

Take advantage of the special pre-order price and get one for your shack today!