SARK-100 Antenna Analyzer Kit

Important notice!

I do not provide support for the SARK-100 derivatives that are currently sold at eBay, AliExpress, and similar sites. These devices are supplied by third parties and I do not have any control over them.

OVERVIEW

The SARK100 Antenna Analyzer Kit is a measurement instrument which determines antenna system performance across the HF/6M amateur bands without the need of connecting the transmitter to the antenna. It is ideal for checking the resonance, bandwidth, and SWR in an easy and fast way. The meter also measures the resistance, reactance, and the magnitude of the impedance.

The analyzer is comprised of a single double-sided printer circuit board PCB (145mm x 81mm) containing all components, controls, and a 2x16 LCD display with backlight; all inside an enclosure that allows in-hand use. The enclosure holds an 8-cell AAA battery pack enabling convenient field use.

The analyzer design is based on a DDS signal generator, a PSoC microcontroller, and a reflectometer for the impedance measurements. The features and flexibility of the PSoC microcontroller allows for a simple hardware design. The design provides an USB interface to allow FW updates and uploading of the real-time measurements to the PC. The development environment is the free PSoC Designer tool and the code has been programmed in 'C' language allowing along the USB update capability the easy customization of the code without the need of acquiring any tool.

The figure below illustrates the block diagram of the analyzer:

The DDS, filter, and power amplifier form a sinusoidal signal generator which frequency and amplitude is controlled by the PSoC micro-controller. The amplitude control allows compensating the roll-off effect of the digital to analog converter in the DDS. The signal generator signal is delivered to the antenna through a reflectometer consisting of an absorptive SWR bridge using matched diode detectors and compensated buffer amplifiers. The data provided by the reflectometer are digitized and used by the micro-controller to compute the SWR and impedance values for each sampled frequency.

The user iteration is provided by a 2x16 display with backlight, a keypad, and a buzzer. In SCAN mode the micro-controller sweeps the signal generator in the selected band looking for the minimum SWR point, the resonant frequency, and the 2:1 SWR limits in order to determine the 2:1 bandwidth. At the end of the scan the resonance frequency is selected and it is shown the impedance values. In manual mode the frequency and bands can be selected using the keypad and allows selecting four operating modes: SWR, complex impedance, capacitance, and inductance.

The analyzer is able to determine the sign of the impedance by a dizzling technique. It takes the measure of the reactance at the selected frequency and compared with the value of the reactance at a frequency slightly higher. In the case that the value of the reactance is greater it is likely that the reactance be inductive (+ j). If the case that value of the reactance is less it is likely that the reactance be capacitive (-j).

The analyzer is designed to be field-usable and operating friendly. It has a convenient form-factor for hand operation and the push-button controls are positioned along the left top side of the unit. The RF connector is located at the top of the unit to provide a convenient connection to the antenna being measured. The external power jack, the USB connector, and the power switch are located in the bottom side of the instrument.

The unit provides both operation from the internal batteries or from an external power adapter. The analyzer software implements some power saving features in order to extend the battery autonomy. The internal batteries are charged automatically by a constant current battery charger when the external power adapter is connected.

FEATURES

• • Automated antenna SWR analyzer

  • Supplied as an easy to assemble kit at an affordable cost

  • Hardware:

    • Powerful and flexible PSoC microcontroller to control instrument operation

    • Precise and self-calibrating reflectometer design measures forward and reflected signals and impedance data

    • Display 2x16 with optional backlight

    • Precision DDS signal generator (AD9851) used as signal source

    • USB port connects to PC for field-upgradeable software and uploading of real-time measurement data

    • Buzzer

  • Software:

    • Microcontroller software programmed in 'C' language

    • Open source GPL license

    • Free PSoC Designer tool and field-upgradeable capabilities allow user customization of the analyzer operation

  • Operation:

    • Manual control option displays SWR and complex impedance at selected frequencies

    • Automatic scanning results displayed as frequencies of lowest SWR and complex impedance

    • Battery operated for field use or use external 13.8V wall adaptor

    • Power saving modes

    • Multi-point calibration for better accuracy

  • Instrument Capabilities:

    • Measure antenna electrical parameters: SWR, impedance (resistance + reactance), capacitance, inductance

    • Measure feedpoint impedance

    • Measure ground loss

    • Adjust antenna tuners and determine loss

    • Measure inductors and capacitors

    • Measure coax transmission line (SWR, length, velocity factor, approximate Q and loss, resonant frequency, and impedance)

    • Measure and determine optimum settings for tuning stubs: SWR, approximate Q, resonant frequency, bandwidth, impedance

    • Determine characteristic impedance of transmission line

    • Determine length of ¼ and ½ wave phasing lines

    • Coaxial Cable Loss

    • Determine antenna tuner loss

    • Measure balun loss

    • Measure inductor Q

    • Estimate quartz crystal parameters

    • Measure magnetic loop resonance and SWR

SPECIFICATIONS

• • Frequency Generation & Control:

    • 1 - 60 Mhz

    • Source impedance: 50 Ohms

    • Stability: +/- 100 ppm

    • Step Size: User configurable increments of 100 Hz, 1 kHz, 10 kHz, and 100 kHz

  • Usable Measurement Range:

    • SWR: 1.0 to 9.99

    • Impedance: approx. 5 to 2000 ohms

  • RF Output:

    • Adjustable: 2.0 Volts pp (typ)

  • Power supply:

    • External: 13.8 to 19 Volts DC, 500mA

    • Internal: 8xAAA 1000mAh NiMH cells

    • Charging time: 12 hours (charge rate 0.1C)

  • Controls:

    • Pushbuttons (5): "Mode", "Band", "Config", "Scan", "Up", "Down"

    • Switch: "Power On"

  • Connectors:

    • RF Out: BNC

    • USB: Mini-B receptacle

    • External power: 2.1mm Power Jack (center pin positive)

HARDWARE

Schematics

Board

Enclosure

SOFTWARE

• • SARK100 Source files: http://sark100swranaly.sourceforge.net/

  • FTDI USB Drivers: http://www.ftdichip.com/Drivers/VCP.htm

  • PSoC Designer: http://www.cypress.com/?rID=34517

BOARD ASSEMBLY

The basic tools needed for the board assembly, see the illustration, are a solder iron (better if it has temperature control), tweezzers, and magnifying glasses; It is also required thin solder wire, solder flux, and 1.5mm solder wick but they are supplied with the kit.The assembly of the board should not take more than four hours.There is a great video explaining surface mount soldering techniques. You will discover that the use of the solder flux and the wick are key for the success of the work.

IMAGES

Below are some images of the SARK100 prototypes:

FILES