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!

viernes, 21 de septiembre de 2012

SARK-110 disponible para compra por adelantado en Seeed Studio

Seeed Studio ha empezado a aceptar pedidos del Analizador de Antenas SARK-110.

El SARK-110 empezará a suministrarse desde principios de Diciembre, pero si visitas el portal Seeed Studio Bazaar desde hoy lo podrás reservar al precio especial de $330 (precio normal: $360).

© EA4FRB - Melchor Varela 2012, Todos los derechos reservados

sábado, 21 de enero de 2012

SARK100 Clones

SARK100 Open Source Hardware (uso no comercial)

Comentar que no tengo intención de continuar con la venta del kit SARK100 ya que he vendido todo el stock que tenía previsto y tengo la intención de sustituirlo por el SARK110.

Por tanto he decidido liberar completamente el diseño incluyendo el hardware para uso no comercial (el software ya era de código abierto).

En el sitio web está publicada toda la información necesaria para la fabricación de las placas para quien quiera realizar el montaje. Hay proveedores que proporcionan el servicio de fabricación de la placa a un precio muy económico, por ejemplo Seeed Studio o ITeadStudio.

La lista detallada de materiales (con códigos DigiKey) no está publicada pero la puedo suministrar bajo petición a mi dirección de correo electrónico.

Esta opción podría ser interesante para clubs o agrupaciones de radioaficionados, ya que es bastante más económico montar un lote de equipos que uno por uno.