FA-VA4 Vector Antenna Analyzer

| enero 13, 2020

FA-VA4 Vector Antenna AnalyzerFA-VA4 Vector Antenna Analyzer Kit

Kit for an easy to use vector antenna analyzer for use in the frequency range 100 kHz to 100 MHz. This kit is an improved version of the IV-Meter from DG5MK.

Easy to build with all SMD parts preassembled. Comes with pre-machined enclosure, selectable menu language (german/english) and english assembly and operating manual. SOL reference elements are included.

Powered by 2 x AA alkaline batteries (not included in kit), average consumption of 50 mA without display backlight.

Size only 5⅜ x 3½ x 1 inch, weighs only 290 g (including batteries).

$139.95 includes shipping and handling

The requirements for construction can be easily handled by beginners if clean working practices and adherence to the instruction manual are followed.

Frequency range 0.1 … 100 MHz
(1 Hz resolution)
Accuracy < 2% f < 50 MHz)
Measurements Complete impedance values
Measurement range s < 100,
limits Z < 1000 Ohms
Input 50 Ohms, BNC
Output voltage Peak to peak = 1 V at 50 Ohms
Power supply 2 x 1.5 V AA batteries
Current drain 49 mA (110 mA)
Case dimensions 137 mm x 90 mm x
25 mm (L x W x H)
Weight 290 g, incl. batteries

Function Test

Before mounting the circuit board into its case a brief test is required. So next first of all, the three caps should be pushed onto the push button switch and the now mounted display plugged into the corresponding sockets. The slider switch should be in the off position (Fig. 8). Lastly two 1.5 V batteries should be attached, making sure of the correct polarity, and the device may be powered up using the slider switch.

The display will briefly show the greetings text, then the FA-VA4 switches to measuring mode. Should the display remain blank then all the previous soldering must be checked and reworked if necessary. When everything is working correctly the slider switch should be turned off and the batteries removed from their holder.

Cautions

The FA-VA4 is a sensitive measuring device. No RF energy must be allowed to reach the measuring socket so as not to destroy the input components. This could happen if for example an antenna in the immediate vicinity transmits. Likewise, static charges should be kept as far away as possible from the measuring socket. Insulated antenna structures must therefor be earthed before connecting to the device for example by shorting to earth.

Rechargeable batteries should not be used in the FA-VA4 as no deep discharge protection nor charging circuitry is available. Deep discharge can render the rechargeable batteries unuseable or even destroy them. Leaking batteries can likewise severely damage the equipment.

The FA-VA4 is optimally designed to use 1.5 V AA cells. Used cells must be removed from the device.

For the longest battery life it is recommended to only use the backlight when the display cannot be read. With daylight or outside the display doesn’t usually needs backlight illumination.

The number of measurement display cycles should only be as many as are needed to ensure a sufficient repetition rate for the measurement in question. Both parameters have a considerable influence on current consumption and therefore on battery

life expectancy, they can be changed in the Setup menu.

BNC plugs should be carefully twisted after connecting to ensure no ‘unexpected’ incorrect measurements.

Directions for use

Although the FA-VA4 has a relatively wide range of functions, its operation is fairly intuitive therefore the following guide has the character of a reference book, however the general operating instructions from the previous section are to be considered in each case.

The device cannot be destroyed by incorrect button pressing but may display incorrect, unexpected results. It is recommended therefore that the inexperienced user starts with data from a known measured object and then explores the antenna analyzer step by step, testing different measurement and display modes, and refer to these instructions as necessary.

For precision measurements the subject of calibration (SOL compensation) is important and is covered in its own separate section.

The antenna analyzer operates according to the following measuring principles: an internal oscillator generates a signal with a defined frequency, this signal is then passed to the test object (e. g. antenna) via the output socket of the device. Due to the electrical properties of the object under

test, the signal will be changed in both amplitude and phase. This change is evaluated to determine the impedance of the test object. All other measured values (e.g. SWR) are mathematically derived from the impedance by the microprocessor.

Controls and connectors

The only connection to the analyzer is the test socket. For operation there are three pushbuttons and an on/off switch.

All selected parameters are saved, so that at switching on the device will have the same settings as when it was switched off. The three pushbuttons have different functions depending on the actual measuring or operating mode. In most cases a function or other selection is called up with the left hand button, the middle and right buttons serve to increase or decrease values through the menulists. The current function is displayed on the display above the buttons.

When in measurement mode a longer press of the left button will call up the menu. The middle and right buttons then allow you to select a menu item which may then be selected or activated using the left button. Other functions of the buttons are explained in a later paragraph.

Switching on the Analyzer

After switching on the FA-VA4 a greetings message will appear on the display under which also the firmware version and to the right of that the battery voltage. The default menu language is English.

The analyzer knows two different modes of SOL compensation.


SOL for all frequencies

It is possible to permanently save SOL reference values for the entire measuring range. In this case, with the Short reference element connected, the analyzer runs through the entire frequency range and stores the determined measured values. The same procedure is to be carried out for connected Open and Load elements. It is recommended to carry out this compensation routine once, after commissioning, for the builtin plug, any permanently attached cable or measuring device and in between times as required. Thereafter the measurement of a test object is possible at any time without further compensation. The analyzer then uses these reference values as a standard (master compensation), in particular for multi frequency measurements. This function can be accessed via the Operating Mode ^ Setup ^ SOL All Frequencies (Fig. 12).

Please note: the entire process takes several minutes but may be cancelled, in this case however the resulting measurements will be inaccurate and the calibration procedure should be recommenced at the first opportunity.

 

Calibration (SOL compensation)

Every extra plug and additional piece of cable influences the impedance measurement of the test object. This unwanted influence can be completely compensated for by the Short Open Load method (shortened to SOL method).

First of all, instead of the test object, three reference elements are measured; Short represents a short circuit, Open, an open cable end, and Load, a resistance in the magnitude of the system impedance (in our case 50 Ohms.) These reference measurements can be easily obtained with acceptable accuracy using three 50 Ohms BNC coax plugs.

In the case of the Short element the inner connector and the plug housing are short circuited, for the Open element the inner pin remains unconnected, for the Load element there is a small 50 Ohm metal film resistor between the inner connector and the housing. If the materials aren’t to hand use the included reference elements (shown in Fig.10 and at page 21).

After calibration has been completed the calculated values are automatically stored in the analyzer so that the correct impedance is determined when the test object is measured.

SOL for an individual frequency

of single frequency calibration the display will show solf, in case of no calibration at all it will show sol-.

 

For all individual frequency measurements it is possible to run through SOL compensation for the actual frequency, (Operating Mode ^ SOL One Frequency, see Fig. 11).

The procedure is the same as described above but only applies to the currently set frequency and therefore runs very quickly. This makes it possible to quickly and easily compensate for temporary changes in the measurement setup or parameters as a result of temperature changes or other interference.

For particularly high accuracy it is recommended to perform such compensation before each measurement.

Important: if the measured frequency of the analyzer is changed, the determined SOL reference values for the current frequency are indicated as invalid and the standard values of the master compensation will be used instead for the next measurement. The display shows which reference values are currently being used. For example in Fig. 18 the master calibration is used to measure SWR, which can be seen as a small solM to the right of the bar on the right hand side of the display. In case

Explanation of the menus

A long press on the left hand button will call up the menu mode. This offers the setup possibilities contained in Tables 2 and 3 (Figs. 13 to 17).

I Operating mode

The operating mode makes it possible to select the measuring and display modes most commonly used in practice.

Single frequency SWR measurement

The indicators become the actual measurement frequency, the standing wave ratio (SWR), the effective impedance resistance (Formula Z), the impedance reactance (+j/j), the SWR shown as a bar graph along with the currently used reference values of the SOL compensation, (solM for master calibration, solf for calibration on an actual frequency, or sol- for uncalibrated operation).

Possible adjustments in the FAV-A4 operating mode

Menu item Meaning
Return Return to the previous mode
SOL One Frequency SOL compensation of the actual frequency
SWR One Frequency SWR measurement of the actual frequency
Z One Frequency Impedance measurement of the actual frequency
SWR Single Sweep Single run of SWR measurement in the specified frequency range
Z Single Sweep Single run of impedance measurement in the specified frequency range
SWR 5 Band SWR measurements of 5 frequencies (5 band measurement)
SWR Cycling Sweep Cyclic SWR measurement run
Z Cycling Sweep Cyclic run of impedance measurement
Frequency Generator RF generator mode
Captured Screens View of saved measurement results (display contents)
Setup Call up the setup menu (see Table 3.)

 

FA-VA4 Setup mode

Menu item Meaning
Return Return to measurement mode
SOL All Frequencies SOL compensation over entire frequency range (master calibration)
5 Band Frequencies Setting the frequency values for 5 band measurements
Language Select the menu language
Backlight Mode Settings for the backlight
Delta Frequency Calibration of the internal frequency
Display Update Cycle Setting the measurement repeat rate
Reset Reset all settings to factory default

 

The actual measurement frequency can be set using the three push buttons. The left button (D/S) selects the decimal place indicated by an underscore line. With the middle or right hand button the values may be increased (+) or decreased (-).

For an eventual compensation (SOL One Frequency) the corresponding function in the operation mode menu must be selected, (see paragraph Calibration). After recording the reference values the analyzer returns to the current measurement mode (Fig. 18).

FA-VA4 Vector Antenna Analyzer Kit

PART LIST

Abbreviation Part description Quantity Note
X2 BNC socket 1
S1 …S3 Pushbutton switches 3
(S1 .S3) Knobs for pushbuttons 3
S4 Slider switch 1
G1, G2 AA Battery holders 2
Graphic display with backlight 1 preassembled but unsoldered
20 pin connector 1 for display
3 pin connector 2 for display
SMD mounted circuit board 1 6 pin connector strip soldered to
Housing, printed 1 upper and lower cover
Case rubber feet 4
Cylinder (grub) screws M3x4 4 board fixing
Cross head screws M3x4 4 for case
Construction and User Manual 1 updated in 8/2017
Type label 1 for sticking to the underside
SOL elements 50 ohm termination 1 made in China
BNC connectors 2

Revised english language construction and user manual. Also now including SOL quick assembly guide.

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