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.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!
© EA4FRB - Melchor Varela 2012, Todos los derechos reservados