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Antenna analyzer on a microcontroller. Antenna analyzer

- a very useful device Many radio amateurs would like to have a "proprietary" antenna analyzer like the MJF259, or similar. But such devices are too expensive ... However, I am sure that every radio amateur has a purchased or home-made RF generator and a frequency meter. Using these two instruments and a differential bridge, you can get a system that can work as an antenna analyzer in many cases.

The circuit shown in the figure was used when tuning HF antennas, from 1.6 to 30 MHz. We need an RF generator operating in this range. A frequency meter is needed to accurately determine this frequency. However, a frequency meter is not necessary if the GHF has a fairly clear and intelligible scale. The signal from the generator is fed to connector X1. Resistor R1 regulates the level (you can not set R1, but use the level controller available on the generator).

The analyzed antenna is connected to connector X2. RF voltage is applied to the primary winding. The RF voltage on the secondary windings of the transformer is supplied to the meter, consisting of a microammeter P1 and a detector on germanium diodes VD1 and VD2. Diodes must be germanium to ensure the highest sensitivity of the meter when indicating minimum readings (balance).

The balance of the bridge is achieved by adjusting the resistor R3 and the variable capacitor C5. These parts must be provided with scales indicating the resistances and capacitances corresponding to the angles of rotation of the handles. The balance is achieved in the case of equality of active and reactive resistances in both arms. Then, having achieved balance, you need to read the values of resistance R3 and capacitance C5. and then calculate reactance C5 from this frequency. Thus, it will be possible to determine the active (R3) and reactive (C5) component of the resistance analyzed antennas.

Pay attention to the capacitance of C3, which is 100 pF, that is, half of the maximum capacitance of C5. If during measurements it turns out that the capacitance C5 in the balance is set to more than 100 pF, then this indicates the capacitive nature of the reactance of the antenna, but the value of C5, set less than 100 pF, on the contrary, indicates the inductive nature of the reactive resistance in the antenna.

Transformer T1 is wound on a 600NN ferrite ring with a diameter of 10 mm. The windings are the same, they are made with a triple folded winding wire of the PEV type with a diameter of 0.35. Eight turns evenly spaced around the ring. The beginning of the windings in the diagram are marked with dots.

The scheme requires adjustment and calibration. The variable resistor R3 and the capacitor C5 must, as already mentioned, be equipped with scales with resistance and capacitance values, respectively (you will need an ohmmeter and a capacitance meter).

Next, connect to X2 antenna equivalent. – resistance 50 ohm, not inductive. On U1 we give a signal of 15 MHz. Set the C5 knob to 100 pF. We increase the voltage from the generator (resistor R1 or generator regulator) to the maximum reading P1. Then, turning the R3 knob, we look for a place with a deep dip in the readings of the device. Further, we make the readings of the device even smaller by adjusting the capacitor C5. On the C5 scale, we make an additional mark, marked "0". This is the point of no reactive component in the load. The gap from the zero point to the maximum value of capacitance C5 should be highlighted by a sector and marked as "Capacitive reactance", and the gap from the same zero point to the minimum capacitance C5 should be highlighted by another sector and marked as "Inductive component of reactivity" Related content:

Antenna Analyzer- a very useful device Many radio amateurs would like to have a "proprietary" antenna analyzer like the MJF259, or similar. But such devices are too expensive ... However, I am sure that every radio amateur has a purchased or home-made RF generator and a frequency meter. Using these two instruments and a differential bridge, you can get a system that can work as an antenna analyzer in many cases.

Next, we connect the equivalent of the antenna to X2. – resistance 50 ohm, not inductive. On U1 we give a signal of 15 MHz. Set the C5 knob to 100 pF. We increase the voltage from the generator (resistor R1 or generator regulator) to the maximum reading P1. Then, turning the R3 knob, we look for a place with a deep dip in the readings of the device. Further, we make the readings of the device even smaller by adjusting the capacitor C5. On the C5 scale, we make an additional mark, marked "0". This is the point of no reactive component in the load. The gap from the zero point to the maximum value of capacitance C5 should be highlighted by a sector and marked as "Capacitive reactance", and the gap from the same zero point to the minimum capacitance C5 should be highlighted by another sector and marked as "Inductive component of reactivity"

When tuning antenna-feeder systems, it is important to correctly measure the standing wave ratio (SWR). This parameter in amateur conditions is usually measured using an SWR meter at a fixed frequency, and the frequency response of the antenna is built by a series of successive measurements. For a single-band antenna, this classical method is quite applicable.

But in order to set up a 7-band HF antenna in this way, in which changing the dimensions of one structural element affects its parameters to varying degrees on several ranges, a lot of effort and time will be required.

Here you need a professional antenna analyzer that will display on the display or laptop screen a graph of the SWR value, as well as the active and reactance of the antenna, depending on the frequency. Convenient and visual. It was to this conclusion that I came when I mounted the GAP TITAN DX all-wave HF antenna on a tiny, hard-won site from my wife at a summer cottage.

In all its urgency, the question arose - to buy a branded antenna analyzer or do it yourself. Considering that this device is needed no more than once a year, and a fair amount of money has already been spent on the purchase of an antenna, I leaned towards the second option.

The antenna analyzer should be as simple as possible, and its setup and calibration should be available at home without the use of any reference instruments. It should provide a panoramic measurement of SWR, X and R with the output of graphs on a computer screen and (or) its own display in the frequency range of 1-30 MHz. Well, of course, the cost of components should be significantly lower than the cost of the cheapest mass-produced antenna analyzer. Conflicting claims...

As a controller, I decided to use the ready-made Arduino Uno R3 debug board. And after a long search and analysis of existing solutions, I found a good version of the antenna analyzer, which is available for DIY.

For the first time, a description of the circuit, design and principle of operation of an antenna analyzer that, in my opinion, satisfies all of the above requirements, was published in the Funkamateur magazine No. 12, 2004. The authors - Davide Tosatti (IW3HEV) and Alessandro Zanotti (IW3IJZ). Magazine "Radiohobby" in No. 1 for 2005. published an abridged translation of this article. Over the decade that has passed since then, the idea has not only not become outdated, but has received further development.

Polish radio amateur Jarek (SP3SWJ) on his website posted a lot of information on the further development of the idea. Many options for circuits and designs from VNA MAX 1 to VNA MAX 6, a lot of links. Frequency range from 1-30 MHz to 1-500 MHz. Unfortunately, the site, in my opinion, is completely "stupid". It is very difficult to understand which firmware and which program for which circuit. Where is the first version, and where is the latest, etc. The complete information necessary for repetition is not easy to catch, and for some schemes it simply does not exist.

Davide (IW3HEV) organized serial production of his antenna analyzer under the miniVNA brand. A beautiful box allows measurements in the range from 100 kHz to 200 MHz, and with an additional unit up to 1.5 GHz. Everything is fine, but almost 400 € for this miracle of technology is a little expensive for a Russian radio amateur ... The scheme and description of miniVNA was published in the magazine “A Radio. Praktica Elektronika" No. 10, 2007

After this brief digression into history, let's get down to business. The block diagram of the VNA antenna analyzer is shown in the figure.

The signal from the DDS-based generator is fed through a directional coupler to the antenna under test. Signals from the direct and reflected wave sensor are fed to a unique chip from Analog Devices - AD8302. At its output, two analog signals are formed. The first is proportional to the ratio of the amplitudes of the input signals, the second is the difference in their phases.

The components for this antenna analyzer are, in general, quite rare, but quite affordable. The problem is that it is impossible to find all the necessary components from one seller. And if you buy in different Russian online stores, transportation costs become too high. Fortunately, there are Aliexpress and eBay. In general, without the help of the fraternal Chinese people, I would not have been able to do anything.

As I already wrote, the main requirement for this design is ease of manufacture and minimum cost. While maintaining the necessary metrological characteristics, of course. Therefore, I used two ready-made modules in the design. The first is a synthesizer module based on the DDS AD9851. A synthesizer chip, a clock generator and all the necessary wiring are mounted on a small board. And this module costs less in China than one DDS chip in Russia.

The second module is "Arduino Uno". This is a popular development board based on the ATmega328 microcontroller. It includes a microcontroller, all the necessary harness and a USB-COM converter for communication with a computer. And again, its cost in China is commensurate with the cost of one microcontroller in Russia ...

But the measuring module had to be assembled independently. Its scheme is shown in the figure. The signal from the DDS module is fed to a monolithic amplifier DA1 type GALI manufactured by Mini-Circuits.

The most important part of the measurement module is the T1 directional coupler. The accuracy and frequency range of the analyzer depend on its quality. This is the so-called "Tandem Match" - a transformer on two-hole binoculars. The technique for making "Tandem match" is described in detail in the article in the Funkamateur magazine mentioned above and in the pdf file, the link to which is at the end of this page.

The antenna is connected to connector X1. In the off state of the relay K1 shown in the diagram, the direct and reflected wave signals from the directional coupler through the 10 db attenuators on the resistors R9, R10, R15 and R11, R12, R16 are fed to the DA3 inputs of the AD8302. Attenuators are needed to avoid overloading the AD8302.

This antenna analyzer can also be used to study the amplitude-frequency characteristics of electrical circuits. When the relay K1 is on, the signal from connector X1 can be applied to the circuit under test, the signal from the output of this circuit is fed to connector X2. Thus, you can adjust the band pass filter, characterize the quartz, etc.

Analog signals proportional to the ratio of the amplitudes and phase difference of the direct and reflected waves from the DA3 output are fed to the ADC of the ATmega328 microcontroller in the Arduino Uno module. Given that a laptop has ceased to be a luxury in our time, I decided at the first stage to abandon my own indicator in this antenna analyzer. All information is displayed on the laptop screen, to which the analyzer is connected via USB interface.

No additional power is required, although the board does have a 5V regulator. This is for future upgrades to be able to work offline. Of course, on the roof with a laptop is not always convenient, but reading information from a large screen is much more comfortable and clearer than from a small display.

The connection of the measuring module to the Arduino board is shown in the figure. I wrote the program for ATmega328 in C in the CodeVisionAVR v2.05.0 environment. It is not necessary to program the Arduino in its proprietary environment. This only makes sense for those who are new to programming.

For those who have an idea about other programming languages, there is no need to understand the syntax and other subtleties of the Arduino language. After all, this is Si simplified to the limit, in which there is no built-in debugger, all hardware modules of the internal periphery of the controller are carefully hidden from the user. And the possibility of assembler inserts is not even out of the question.

There are, of course, advantages to the Arduino. The main one, in my opinion, is the ability to download the program to the controller without a programmer, using the USB-COM converter mounted on the board. How to do this, read the full description, the link at the end of this page. First you need to download the latest Arduino software from the official website and install the USB-COM converter driver from it.

To load a HEX file into the Arduino Uno, you will also need the XLoader program, the archive with the distribution kit of which must be downloaded from its author's website. There is a local link at the end of the page. Working with the program is simple and intuitive, details in the full description.

A few words about the parts used. All resistors and non-polarized SMD capacitors are sizes 1206 or 0805. Inductors L1 and L2 can be either SMD or conventional through-hole. Resistors R4 and R6 are calibration resistors, the need for their installation and ratings are determined during commissioning. Stabilizer DA2 is not used in this version, because. The analyzer is powered by USB. It is set for future design development.

Pay attention to the setting of jumpers on the DDS module. They must be installed exactly as shown in the figure - J1 and J3 are closed, the rest are open. The diagram and description of the DDS module can also be downloaded from the link at the end of the page.

For adjustment, it is desirable to have an RF voltmeter, and preferably an oscilloscope with a bandwidth of at least a few megahertz and a frequency counter. In extreme cases, you can get by with an RF probe on a diode and a multimeter. Here I will not describe the setup in detail, those who wish can familiarize themselves with it in full description,

The antenna analyzer operates under the control of the Ig_MiniVNA program. Its latest version until recently could be downloaded from http://clbsite.free.fr/. Unfortunately, in 2015 the link stopped working. So download from my site. Link below. This is the latest version of the program. Indeed the latter, because according to the author, when the computer crashed, he lost everything... But the program works both on Windows XP and on Windows 7 64 bit.

Working with the program is simple and intuitive, see the full description for details, as well as on the SP3SWJ website. This site is unfortunately only in Polish and in a big mess...

For example, I give the view of the program window when examining my antenna in the range of 40m. It is clearly seen that the resonance is shifted down in frequency. Needs to be set up.

The frequency range of the analyzer is determined primarily by the directional coupler, the material of its core, the accuracy and symmetry of the winding. The upper limit of the frequency range depends on the type of DDS. The theoretical limit is half the DDS clock frequency, in this case 90 MHz. Really satisfactory parameters are provided up to a frequency of no more than 1/4 clock, i.e. up to 45 MHz. But more than 30 MHz for a HF antenna is not necessary.

The antenna analyzer can be run by another program - vna / J, which was written by Dietmar Krause (DL2SBA). It can be downloaded from his website. The program is written in JAVA and can work not only under Windows, but also under Linux and Mac.

Of course, you must first install JAVA on your computer. The vna/J interface is similar to IG_MiniVNA. Only after starting the program from the list of supported devices you need to select miniVNA. Working with these programs is almost the same. For vna/J, the "Manuals" page of the DL2SBA website has detailed instructions for installing the software, calibrating the analyzer, and a user manual.

If you are interested in this design, you can read the full description, download the printed circuit board drawing of the measuring unit in the Sprint Layout format, its diagram in the sPplan format, as well as a detailed method for manufacturing the Tandem match directional coupler, firmware and a draft program for the Arduino Uno. For convenience, I post all the articles from the magazines mentioned above, as well as the Ig_MiniVNA and XLoader programs.

Attention! When manufacturing a printed circuit board, it should be borne in mind that the relay used in the circuit is sensitive to the polarity of the winding connection. If a voltage of reverse polarity is applied to the winding, the relay will not work. This can lead to errors in instrument calibration. Therefore, before manufacturing a printed circuit board, you should clarify from the datasheet where you need to give a plus, and where a minus. You can simply apply 5 volts to the winding and make sure that the contacts are flipped. If the polarity of the relay you used does not match the printed circuit board, you should correct the track pattern. If the board has already been made, you will have to cut the tracks - swap the connection of the winding leads. You can make sure that the relay works in the already assembled analyzer by disconnecting the “Rele” wire from the Arduino and connecting it to +5 V.

In our time, radio waves have ceased to be something unknown. Radio amateurs began to appear everywhere. In their work or hobby, a device such as an antenna analyzer is directly involved. What it is, what types of it exist and how it works will be discussed later in this article.

RigExpert analyzer

There are many different models, but only a few of them will be considered in the article. One of the multifunctional devices is RigExpert AA 600. The purpose of this device is to set up, check and repair antennas, as well as antenna-feeder paths. The key indicators of this device are SWR - standing wave ratio - and impedance. Both of these characteristics have a graphical display on this device.

In addition, there are additional features such as graph memory, connection to a computer, as well as easy-to-use measurement modes. All this makes the RigExpert AA 600 model quite acceptable for use by both professionals and amateurs. Also, this device has two more distinctive measurement modes that make it stand out from the crowd, these are MultiSWR ™ and SWR2Air ™. To make it much easier to find any faults on cable lines, this antenna analyzer has a built-in mode for analyzing discontinuities along the transmission line.

Specifications

RigExpert antenna tuning device has the following technical parameters:

The frequency range of the device is from 0.1 to 600 MHz.
The frequency input resolution or frequency for this instrument is 1 kHz.
It is possible to carry out measurements with this device in systems with a resistance of 25, 50, 75, 100 Ohms.
The measurement range of the standing wave ratio (SWR) in numerical values is from 1 to 100, and in graphical mode - from 1 to 10.
The SWR is displayed as a filled bar or as a digital readout.
There is an optional calibration option in the SWR graphical mode, as well as on R, X and Smith's pie chart.

This model can be powered from the following sources:

Alkaline batteries in the amount of 3 pieces with a voltage of 1.5 V each. The standard size for these batteries is AA.
Nickel-metal hydride batteries also in the amount of 3 pieces, each of which has a voltage of 1.2V, and a capacity of 1800 to 3000 mAh.

The operating time of this model is a maximum of 3 hours in continuous measurement mode, or two days if the device is in "standby" mode. These time intervals are suitable for freshly charged batteries of the device.

Precautionary measures

There are a few rules to follow when using this antenna analyzer.

It is strictly forbidden to make any measurements or simply connect the device to the antenna during a thunderstorm. A lightning strike, as well as the static voltage that accumulates in the antenna, are deadly to humans.
Do not leave the device connected to the antenna after the work has been completed. A thunderstorm or another nearby transmitter may disable it.
It is forbidden to apply high-frequency signals to the input of the device, as well as turn on the transmitter if there is already another working radio wave transmitter nearby.
The cable must be earthed before connection. This is divided in order to avoid electric shock from the static electricity present in the cable.
It is not recommended to leave the antenna tuner switched on when all necessary measurements have been made. This will interfere with nearby transmitters.

Overview of the SARK model

The device of this company appeared quite a long time ago and at one time was the best in terms of such a ratio as price-quality. But even today this device is quite successfully operated and is in demand.

The SARK 110 is a vector complex resistance meter. The measurement is carried out in the range from 0.1 to 230 MHz. In addition, this device also displays SWR and R-L-C in serial as well as parallel equivalent. In addition to these indicators, the device also shows the quality factor, phase, reflection coefficient of the connected load. In addition, it can measure the length of the cable and the distance to the moment where the inhomogeneity is located.

Data output is carried out on a 3-inch screen as conventional Voltaire-Smith pie charts or as conventional numerical indicators. If the screen seems too small, it is possible to connect the device to a computer via a USB cable and display data on its monitor.

The purpose of the SARK model

It is worth saying that this antenna analyzer is a very serious device that has a large set of a wide variety of functions. In order to describe them all, it will take quite a lot of time, and therefore only the main ones will be given.

The device has a synthesizer to perform the following functions:

Possibility of direct digital synthesis with an accuracy of 1 Hz.
Sinusoidal output signal.
Operating frequency range from 0.1 to 230 MHz.

This model can also measure the following parameters:

Complex impedance in series and parallel equivalents, in rectangular or polar coordinates.
Reflection coefficient in the same rectangular or parallel equivalents.
SWR, return loss, and percentage of reflected power.
The last thing this analyzer can measure is the quality factor, inductance and equivalent capacitance.

Features of work

This antenna analyzer is endowed with some general features that apply to all types of work that this model can perform.

It has the ability to preset for all amateur bands that fall within the band of the device.
Has adjustable reference impedance.
It is possible to save all the collected data in the analyzer's memory, and then recall them from there if necessary.
It has presets for most popular cables used for connection.
It is possible to add or subtract the transmission coefficient.
white or black.
It is possible to manually adjust the thickness of the graphs.

In addition to analysis, this device can also perform the following types of work:

Construction of rectangular graphs.
Building a Smith Pie Chart.
single frequency mode.
Cable measurement.
Field mode.
Multiband mode.
High frequency generator.

It is also worth adding that the battery life of this device is approximately 2.5 hours.

Analyzer AA-330M

The purpose of this device is to study the characteristics of the HF antenna-feeder device. The device is portable, and it is located in a case, which is made of impact-resistant plastic. The model has a wide range of features that will suit both professionals and amateurs. The AA-330M antenna analyzer is equipped with an interface that allows you to communicate with a computer, and also has software, which further expands the possibilities for studying the characteristics of various antennas. This model can operate in automatic mode, in which it will scan the selected frequency range. It can also work in manual mode, in which it has a convenient step encoder, which, in turn, has a button function so that you can quickly and conveniently select parameters.

Device Capabilities

The model has a wide variety of options. When taking measurements, the screen of the device displays such parameters as SWR, frequency, active and reactive components of resistance, as well as the sign of reactivity. At the same time, all graphs that can be saved at the moment will be displayed on the computer screen. This feature is very convenient as these graphs can be called up later to be analyzed simultaneously with new measurements from other antennas. Thus, it is possible to compare the performance of new antennas with old ones that were dismantled long ago. Another very convenient feature is the automatic finding of the resonant frequency by the instrument while scanning the selected range. This saves a lot of time and also reduces the amount of effort required to tune the antenna. When turning the encoder knob, it is possible to scan all frequencies in steps of 1, 10, 100, 250 kHz.

Functions of model AA-330M

Model AA-330M has the ability to work as a sinusoidal current generator, which generates an output signal level of 1.4 V. There is also the possibility of step adjustment in 1, 10, 100, 250 kHz. Another of the functions of the device is the ability to work with two different feeder lines - 50 and 75 ohms. To do this, the device has two different measuring bridges. The device is equipped with a function to turn off the backlight on the screen. This action is used when using the device in the "field" conditions and makes it possible to increase the time of the analyzer by about 30%. There is also another function that allows you to record all the data received after scanning to the volatile memory of the device. There is the possibility of subsequent output of the recorded data to the monitor screen, and the graphs are saved when the device is turned off. The accuracy and reliability of this instrument has been verified in numerous experiments with R-SQUAD antennas.

Antenna-feeder system

This system is designed to perform several functions.

The first function of this system is the reception of interrogation signals, as well as the transmission of response signals in the sector in which the localizer operates.
The second is to ensure the joint operation of the receiving and transmitting devices on a common antenna. It also ensures that work is switched to a backup set if the main worker fails for any reason.

It is also important to note that the antenna-feeder system consists of two components - this is the antenna system, as well as the feeder path. In turn, the first of these two elements includes eight different emitters, as well as one power divider, which distributes it in eight different directions. And the feeder system includes components such as four directional couplers, as well as two coaxial connecting cables that absorb loads.

SWR value

Currently, SWR meters are quite common and widely used. The value of these devices is great, in addition, the measurement of SWR, that is, the standing wave ratio, is widely used in antenna analyzers. However, despite the significant role of this equipment, few people know for sure what such an SWR meter measures separately or built into the analyzer. It is known for sure that the standing wave ratio in the feeder is determined by two parameters. These include the input impedance of the antenna and the characteristic impedance of the feeder. It is also important to note that in the practical part, most often the measurement of these indicators must be carried out at a small distance from the antenna itself. Most often this place is the transceiver.

How to set up TV

In order to set up MTS TV, there are two ways. One of them is quite simple. It consists in purchasing the recommended kit with a multimedia set-top box. The advantage of this method is that in such a set all channels will already be tuned. However, when using the MTS TV CAM module, Verimatrix will have to configure all the channels yourself. In order to do this, you can use the lists of transponders distributed on the Internet, as well as the frequency bands attached to them. To search for the required frequencies and tune them, you can also use the antenna analyzers described above.

An Antenna Analyzer - A Very Useful Tool Many hams would like to have a "proprietary" antenna analyzer like the MJF259 or similar. But such devices are too expensive ... However, I am sure that every radio amateur has a purchased or home-made RF generator and a frequency meter. Using these two instruments and a differential bridge, you can get a system that can work as an antenna analyzer in many cases.

14.02.2022

A computer

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