HF antenna matching devices are necessary for the installation of amateur and professional radio points. As a rule, the cost of such equipment is low. They are sold openly, and to buy matching devices for HF antennas, no special permission is required.
Application area
HF antenna tuners are necessary for almost all people who practice radio communications. HF antenna tuners tend to buy and install in the following categories:
- fishermen, hunters, tourists and other amateurs active rest Outdoors;
- Truckers and taxi drivers also prefer to install an antenna tuner for the transceiver in their cars;
- Today, Russia cannot boast that there is a stable coating throughout its entire territory. cellular communications. In many populated areas, the only means of communication is a radio station, complete with which people tend to buy a matching device for an HF transmitter.
Based on the above, it becomes clear that integral part Amateur radio points include not only transceivers, walkie-talkies and antennas, but also tuners. As a rule, the price of such devices is low and affordable for a radio amateur with average income.
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Among shortwave radio amateurs, MFJ antenna tuners of various modifications are popular, including those with a power of 1...3 kW. The author of the article has more than once seen the “insides” of tuners from this company that have failed. It is possible that with more “delicate handling” such disastrous consequences can be avoided, but this is not a factor in the high reliability of the tuner. Their cost also plays an important role...
Currently, on the CIS radio markets, including on the Internet markets, a lot of radio components from military equipment of the USSR, removed from service, but quite suitable for amateur radio designs, have appeared.
Having studied information on MFJ hand-held T-tuners and various “homemade” devices, the author assembled a tuner for a maximum throughput power of 3 kW in the amateur radio ranges 1.8...30 MHz, using the appropriate components.
The device is a complete structure and allows:
1. Connect an external 50 Ohm load to the power amplifier (PA) through an SWR and throughput power meter.
2. Switch two antennas through an SWR and throughput meter directly without a tuner.
3. Connect one antenna to the tuner through an SWR and throughput power meter and match the load equivalent to a resistance of 10...1000 Ohms in the range of 1.8...30 MHz.
4. Measure the SWR in the connected antenna-feeder system with a minimum power of 50 W into a 50 Ohm load.
5. Measure the power of the transmitted signal in three intervals: 0.3 kW, 1.5 kW, 3 kW.
6. Suppress out-of-band emissions (at least 10 dB).
Schematic diagram antenna tuner is shown in Fig. 1. The transmitter signal is supplied to connector XW1 and, through the primary winding of transformer T1 of the SWR and throughput meter, goes to the switch for selecting the direction of power transmission - SA2. In position 1 of switch SA2, the signal is sent to connector XW2, to which a non-inductive load with a resistance of 50 Ohms is connected to the corresponding power. This mode is required to configure tube amplifier power to prevent breakdown of variable capacitors (VCA) of the P-circuit. It often happens that radio amateurs in the P-circuit of high-power tube amplifiers use capacitors with fairly small gaps, for example, three- or five-section KPIs with a section capacity of 12/495 or 17/500 at best.
Rice. 1. Schematic diagram of the antenna tuner
In positions 2 and 3 of switch SA2, the transmission signal can be supplied to connectors XW3 and XW4, respectively, to which antenna-feeder devices with a characteristic impedance of 50 Ohms are connected. In position 4 of switch SA2, the transmission signal will go to the tuner and then to connector XW5, to which an antenna feeder device with a resistance of 10...1000 Ohms can be connected.
The tuner is made according to a T-shaped circuit and consists of two KPIs C6 and C7, a coil with variable inductance L1 and capacitors C8, C9, which are automatically connected by switches SA3 and SA4 when the rotors of KPIs C6 and C7 rotate.
When measuring throughput power, the RF signal is removed from the secondary winding of transformer T1 through the circuit VD1C3R3 and through contacts 1, 2 or 3 of switch SA1 and the corresponding additional resistors R4-R8 is supplied to the measuring device PA1.
When measuring SWR, the signal is removed from the secondary winding of transformer T1, detected by circuits VD1C3R3 and VD2C4R3, through contacts 4 or 5 of switch SA1 from the variable resistor R3 motor to device PA1. Circuit VD1C3R3 is a direct wave detector, circuit VD2C4R3 is a reflected wave detector. The variable resistor R3 sets the position of the arrow of the PA1 device to the final scale division in position 4 of the SA1 switch. In position 5 of switch SA1, the SWR readings are read. The PA1 measuring device has two scales: a power throughput scale and an SWR reading scale.
The main components in the design are used from the matching-balun device of the R-140 radio station. The measured capacitance of capacitors C6 and C7 is 26...206 and 26...209 pF, respectively. The thickness of the duralumin plates of the KPE rotor and stator is 3.7 mm. The gap between the rotor and stator plates when the rotor is inserted is 7 mm. The rotors of these KPIs rotate 360° without restrictions (Fig. 2). When choosing a different type of KPI, you need to pay attention to the thickness of the plates, since thin plates can bend with a high-power signal, thereby contributing to RF breakdown. The used KPIs have powerful brush commutators made of brass. With their help, additional capacitors C8 and C9 - K15U-1 are connected for a rated voltage of 3.5 kV and a reactive power of 8 kVAr.
Rice. 2. KPE rotors
Cylindrical variometer L1 - also from the R-140 radio station. Its coil is made of a 10x1.2 mm copper bar and contains 22 turns with a pitch of 6 mm. The variometer can also be used from other equipment, but not with worse data.
Switch for selecting the connected load SA2 - brush type, ceramic with a contact area of at least 7 mm 2. Switches with a spherical contact shape are not suitable due to the small contact area. Switch SA1 - PGK 5P2N or another suitable type on radio ceramics.
Transformer T1 is wound on a magnetic conductor of standard size K20x10x5mm made of 50HF ferrite. The primary winding T1 is a copper conductor with a diameter of 3 mm and a length of 40 mm, on which a fluoroplastic tube is placed. This conductor passes through a ferrite ring with a secondary winding, which is made of two parallel stranded wires taken from the installation cable. PVC-insulated wires contain two cores of seven conductors of tinned copper wire with a diameter of 0.15 mm. This winding contains ten turns wound evenly around the ring. The ring is pre-wrapped with fluoroplastic or varnished fabric tape. The midpoint of the secondary winding is obtained by connecting the end of one winding wire to the beginning of the second.
The author has long been using this type of secondary winding in the manufacture of SWR meters up to 50 MHz, which has proven itself to be the most optimal and reliable. It should be borne in mind that the upper terminal of capacitor C1 is connected to the conductor of the primary winding T1 after it (not from the side of the input connector!). The common wire bus of the meter is made of copper wire with a diameter of 3 mm. One end of this bus is connected to the housing of the input connector, and the other - to the braid of the cable going to the SA2 switch. The central wire of this cable is soldered to the conductor of the primary winding T1 after it.
Capacitor C1 - any suitable one with an air dielectric, C2 - KSO-1, KTK, KDK for a rated voltage of at least 250 V. Resistors R1, R2, R6, R8 - MLT-2. Variable resistor R3 - SP3-9a, SP3-4a or SP group B. Trimmer resistors R4, R5, R7 - SP3-9a, SP4-1 group A. Capacitors C3, C4 are made up of two KDK capacitors with a capacity of 6800 pF, connected in parallel, C5 - CDC. All capacitors are for a rated voltage of 250 V. Diodes VD1, VD2 can be replaced with selected D9Zh diodes. Device PA1 - M24 with a total needle deflection current of 200 μA. You can use another one for a current from 50 to 300 μA with appropriate correction of additional resistors. The minimum power of SWR control depends on the sensitivity of the device. In the author's version it is 50 W. The choice of such power was made for reasons of comfortable operation of the tuner at the time of matching with a high load resistance.
All RF connectors are SR-50-165F. To connect the equivalent load of 50 Ohms, a 50 Ohm connector of a different type is used, so as not to be confused with other directions.
The tuner is mounted in a housing measuring 480x320x300 mm from the G3-33 generator. Rubber feet are screwed to the bottom of the case, and holes for connectors are cut out in the back wall. There is also a ground terminal on the rear wall of the housing.
The tuner's front panel and chassis are made of 1.5 mm thick steel and are a one-piece rigid structure. They are connected by semi-automatic welding (SEW), but a rivet-screw connection method can be used. It is important that the design be sufficiently rigid, since the radio components used are relatively large in size and weight. The RF connector mounting panel with dimensions of 442x75x4 mm is made of duralumin and mounted on the rear of the chassis. The connectors are secured with brass screws and M3 nuts. Mounting tabs made of tinned brass of suitable size are secured under brass nuts. In the design, all areas for screws, nuts, tabs and connectors are thoroughly cleaned before installation. The front panel and chassis of the tuner are painted with PF-115 enamel gray. All inscriptions are made in transferable font (Fig. 3).
Rice. 3. Tuner front panel
Rectangular windows are cut out in the side walls of the chassis at the mounting points for the gearbox and variometer to reduce installation capacity. The units of the measuring device, SWR meter and throughput power are covered with box-shaped screens. The SWR and throughput meter unit is additionally covered with an L-shaped duralumin screen.
The layout of the tuner components is shown in the photo (Fig. 4).
Rice. 4. Layout of tuner components
When installing control units, it should be taken into account that they are isolated from the chassis. The metal control axes of the KPI are connected to the axes of the KPI rotors through insulating high-
covolt couplings. Also on the control axis are disks with a diameter of 100 mm made of metal or plastic for scales. Scales are made on a printer or drawn by hand on thick white paper. The working field of the KPI scales is 360 o. In the front panel of the tuner, holes are cut out in place for these scales. The holes are covered with plexiglass plates 1 mm thick and equipped with sights in the center. The scale of the PA1 device is made in the same way.
Capacitors C8 and C9 are mounted on rear walls buildings C6 and C7, respectively. When installing the variometer, pay attention that the control axis of the variometer is connected to its moving contacts. Therefore, the current collector of the moving contacts is connected to the nearest terminal of the variometer coil and connected to a common wire - the HF connector mounting plate. A modernized scale mechanism from the 10RT-26 radio station was used as a variometer scale device. The variometer scale is also made using the above method.
The tuner is installed using a coaxial cable RK50-9-12, designed for a throughput power of more than 3 kW at SWR=1. The PA1C5R3 measuring unit is connected by shielded low-frequency wires. The remaining connections are made with a tinned copper busbar 10x1 mm and a tube with a diameter of 5 mm along the shortest path. Parts C1-C4, R1, R2, VD1, VD2 are mounted in a hinged manner on a ceramic plate with mounting tabs. As mentioned above, capacitors C3 and C4 are made up of pairs of capacitors with a capacity of 6800 pF. Some are installed on the plate, and the second - on the SA1 switch. Trimmer resistors R4, R5, R7 are mounted on the side panel of the chassis for external regulation (Fig. 5). There is also a hole made for adjusting capacitor C1. The SA1 switch position lock must be loosened slightly for smoother switching. The switch axis SA1 is brought to the front panel of the tuner through an axis with two spring cardans. Variable resistor R3 is also installed on the front panel. Elements R3, PA1, C5 are covered with a box-shaped screen. Diodes VD1, VD2 must be matched in pairs. Simplified selection - by measuring direct resistance with a digital resistance meter. For a more accurate selection of diodes, you can use well-known methods from the literature or the Internet.
Rice. 5. Installation of resistors
All work on setting up the tuner is carried out in strict compliance with electrical safety precautions! Tuning is performed on the 14 MHz band. On other ranges the results are quite acceptable, and no additional settings not required.
First, check that the entire device is installed correctly. After making sure that everything is in order, set the SA2 switch to position 1 (“50E”) and connect a 50 Ohm non-inductive resistor of the appropriate power to the XW2 connector. Connect the output of the transceiver or power amplifier to connector XW1. The motor of the variable resistor R3 is set to the extreme right position (the moving contact is connected to the common wire). Switch SA1 is set to position 4 (“F”, direct wave). Switch the transceiver into transmit mode, configure its P-circuit for a load of 50 Ohms and set the output power to 50 W. If the transceiver has a transistor output, then it is already set to 50 Ohms. Using variable resistor R3, set the arrow of instrument PA1 to the middle of the scale. Move SA1 to position 5 (“R”, reflected wave) and use a dielectric screwdriver to rotate the rotor of capacitor C1. The arrow of the PA1 device goes to zero. Return SA1 to position “F” and use resistor R3 to set the PA1 arrow to the final scale value. Switch SA1 to position “R” and use capacitor C1 to set the PA1 arrow to the zero scale mark. Repeat this operation and, if necessary, adjust the setting. This setting will correspond to an SWR of one. The SWR meter scale is calibrated according to calculations using the formula
SWR = (1+U neg)/(1-U neg).
Instead of 1, substitute the final value of the scale, instead of U - the readings in the reflected wave mode. The resulting value will be the SWR value. For example, the entire scale has 100 divisions. The reflected wave reading is ten divisions. We substitute these values into the formula and do the calculation:
SWR = (100+10)/(100-10) = 1.22.
The resulting value will correspond to the SWR at this point on the scale. In this way you can calculate the entire scale of the SWR meter. By varying the numbers in this formula, you can calibrate the scale to the desired values.
Next, we set up a throughput power meter, which has three multiple measurement limits: 0.3 kW, 1.5 kW and 3 kW. To set up, you will need an RF voltmeter with a voltage measurement limit of 400 V. For these purposes, voltmeters that come with RF voltage dividers are suitable. Why up to 400 V? Because with a power of 3 kW at a load of 50 Ohms there will be an RF voltage of 387 V, with a power of 1.5 kW - 274 V, with 0.3 kW - 123 V. These values are obtained by calculation using the formula
Using the same formula, intermediate values of the throughput power meter scale are determined. It should be noted that the power scale is nonlinear, and it will not be possible to use the linear scale of the PA1 device directly to read power.
In the throughput power meter mode, the slider of the variable resistor R3 is set to the zero position. Switch switch SA1 to position 1 (0.3 kW), transmission level is at zero. Trimmer resistors R4, R5, R7 are set to the position of maximum resistance. They smoothly apply the input signal and control the RF voltage into a 50 Ohm load. When the voltage reaches 123 V, the tuning resistor R4 sets the pointer of the PA1 device to the final scale value. This position will correspond to a throughput power of 0.3 kW. In a similar way, the meter is adjusted in other positions of SA1 in accordance with the RF voltages, the values of which are given above. Initially, additional resistors R6 and R8 have a resistance of 200 kOhm and 470 kOhm, respectively. When setting up, you may have to select them. They provide smooth adjustment with trimming resistors R5, R7.
Intermediate power values are obtained from the formula. You probably shouldn't create a lot of values. It is enough, for example, to digitize the following: 100 W, 200 W, 250 W, 300 W. The multiplier will give: 0.5 kW, 1 kW, 1.25 kW, 1.5 kW or 1 kW, 2 kW, 2.5 kW, 3 kW.
Connect to the tuner ground (terminal X1), a load resistance of 50 Ohms (connector XW2), the output of the transceiver/amplifier (connector XW1) and a matching antenna (to connector XW5).
Move switch SA2 to position 4 "TUNER". Turn on the transceiver in receive mode and rotate the variometer adjustment knob L1 until maximum air noise is obtained. Set the transmit power to about 50 W and adjust the capacitors C6 and C7 to achieve a minimum SWR. In practice, it is better to rebuild capacitor C6 in small increments, then fine-tune to the minimum SWR with capacitor C7. If necessary, adjust coil L1, but this is the last thing. The procedure is repeated until the minimum SWR is achieved. Once it is received, the output power of the transmitter can be increased.
It should be borne in mind that the minimum SWR can be obtained in different combinations of tuner knob positions.
Once the minimum SWR is reached, you should check the power output of the transmitter to ensure that its ALC system has not significantly reduced it. If this does happen, you should look for the minimum SWR at a different position of the variometer. In order not to search for tuner tuning points each time, it is useful to make a table of the position of the tuning knobs by range section.
It must be remembered that the tuner should be tuned at a power of less than 100 W! Increase the power only after setting up the tuner and do not use the transmission mode for a long time at high SWR.
Some reminders. If an antenna power feeder is used with a length that is an odd multiple of 1/4λ (taking into account the shortening factor), then the feeder turns into a high-resistance transformer. If the length of the feeder is an even multiple of 1/4λ, then we have a repeater of the antenna input impedance. That is, the input impedance of the antenna will be connected to the tuner. This should be taken into account when building both single-band and multi-band antennas in order to obtain their maximum efficiency.
Publication date: 02.07.2018
Readers' opinions
- Sergey / 12/10/2018 - 10:54
Greetings! where can I order this?
Antenna matching devices. Tuners
ACS. Antenna tuners. Scheme. Reviews of branded tuners
In amateur radio practice, it is not so often possible to find antennas in which the input impedance is equal to the characteristic impedance of the feeder, as well as the output impedance of the transmitter. In most cases, such a correspondence cannot be detected, so it is necessary to use specialized antenna matching devices. The antenna, feeder and transmitter (transceiver) output are included in unified system, in which energy is transferred without any loss.
All-range matching device (with separate coils)
Variable capacitors and biscuit switch from R-104 (BSN unit).
In the absence of the specified capacitors, you can use 2-section ones from broadcast radio receivers, connecting the sections in series and isolating the body and axis of the capacitor from the chassis.
You can also use a regular biscuit switch, replacing the rotation axis with a dielectric one (fiberglass).
Details of tuner coils and components:
L-1 2.5 turns, AgCu wire 2 mm, coil outer diameter 18 mm.
L-2 4.5 turns, AgCu wire 2 mm, outer diameter of the coil 18 mm.
L-3 3.5 turns, AgCu wire 2 mm, outer diameter of the coil 18 mm.
L-4 4.5 turns, AgCu wire 2 mm, outer diameter of the coil 18 mm.
L-5 3.5 turns, AgCu wire 2 mm, outer diameter of the coil 18 mm.
L-6 4.5 turns, AgCu wire 2 mm, outer diameter of the coil 18 mm.
L-7 5.5 turns, PEV wire 2.2 mm, outer. coil diameter 30 mm
L-8 8.5 turns, PEV wire 2.2 mm, outer. coil diameter 30 mm
L-9 14.5 turns, PEV wire 2.2 mm, outer. coil diameter 30 mm
L-10 14.5 turns, wire PEV 2.2 mm, outer. coil diameter 30 mm.
It was urgent to launch 80 and 40 m in someone else's house, there was no access to the roof, and there was no time to install an antenna.
I threw a vole a little over 30 m from the third floor balcony onto a tree. I took a piece of plastic pipe with a diameter of about 5 cm and wound about 80 turns of wire with a diameter of 1 mm. I made taps at the bottom every 5 turns, and at the top every 10 turns. I assembled this simple matching device on the balcony.
I hung a field strength indicator on the wall. I turned on the 80 m range in QRP mode, picked up a tap on top of the coil and used a capacitor to tune my “antenna” to resonance according to the maximum of the indicator readings, then picked up a tap at the bottom to the minimum of the VAC.
There was no time, and therefore I didn’t put up biscuits. and “ran” along the turns with the help of crocodiles. And the entire European part of Russia responded to such a surrogate, especially at 40 m. No one even paid attention to my vole. This is of course not a real antenna, but the information will be useful.
RW4CJH info - qrz.ru
Matching device for low frequency range antennas
Radio amateurs living in multi-storey buildings often use loop antennas on the low frequency bands.
Such antennas do not require high masts (they can be stretched between houses at a relatively high altitude), good grounding, a cable can be used to power them, and they are less susceptible to interference.
In practice, a triangle-shaped frame is convenient, since its suspension requires a minimum number of attachment points.
As a rule, most shortwave operators tend to use such antennas as multi-band antennas, but in this case it is extremely difficult to ensure acceptable matching of the antenna with the feeder on all operating bands.
For more than 10 years I have been using a Delta antenna on all bands from 3.5 to 28 MHz. Its features are its location in space and the use of a matching device.
Two vertices of the antenna are fixed at the roof level of five-story buildings, the third (open) is on the balcony of the 3rd floor, both of its wires are inserted into the apartment and connected to a matching device, which is connected to the transmitter with a cable of arbitrary length.
At the same time, the perimeter of the antenna frame is about 84 meters.
The schematic diagram of the matching device is shown in the figure on the right.
The matching device consists of a broadband balun transformer T1 and a P-circuit formed by a coil L1 with taps and capacitors connected to it.
One of the options for transformer T1 is shown in Fig. left.
Details. Transformer T1 is wound on a ferrite ring with a diameter of at least 30 mm with a magnetic permeability of 50-200 (non-critical). The winding is carried out simultaneously with two PEV-2 wires with a diameter of 0.8 - 1.0 mm, the number of turns is 15 - 20.
The P-circuit coil with a diameter of 40...45 mm and a length of 70 mm is made of bare or enameled copper wire with a diameter of 2-2.5 mm. Number of turns 13, bends from 2; 2.5; 3; 6 turns, counting from the left according to the L1 output circuit. Trimmed capacitors of the KPK-1 type are assembled on studs in packages of 6 pieces. and have a capacitance of 8 - 30 pF.
Setup. To configure the matching device, you need to connect the SWR meter to the cable break. On each band, the matching device is adjusted to a minimum SWR using adjusted capacitors and, if necessary, selecting the position of the tap.
Before setting up the matching device, I advise you to disconnect the cable from it and set up the output stage of the transmitter by connecting an equivalent load to it. After this, you can restore the connection between the cable and the matching device and perform final adjustments to the antenna. It is advisable to split the 80-meter range into two sub-bands (CW and SSB). When tuning, it is easy to achieve an SWR close to 1 on all ranges.
This system can also be used on the WARC bands (you just need to select the taps) and on 160 m, accordingly increasing the number of coil turns and the perimeter of the antenna.
It should be noted that all of the above is true only when the antenna is directly connected to the matching device. Of course, this design will not replace the “wave channel” or “double square” at 14 - 28 MHz, but it is well tuned on all bands and removes many problems for those who are forced to use one multi-band antenna.
Instead of switchable capacitors, you can use KPE, but then you will have to tune the antenna every time you switch to another band. But, if this option is inconvenient at home, then in field or hiking conditions it is completely justified. I have repeatedly used reduced delta options for 7 and 14 MHz when working in the field. In this case, two peaks were attached to trees, and the supply was connected to a matching device lying directly on the ground.
In conclusion, I can say that using only a transceiver with an output power of about 120 W for operation on the air without any power amplifiers, with the described antenna on bands 3.5; 7 and 14 MHz have never experienced any difficulties, while I usually work on a general call.
S. Smirnov, (EW7SF)
Design of a simple antenna tuner
Antenna tuner design from RZ3GI
I offer a simple version of an antenna tuner assembled in a T-shape.
Tested together with FT-897D and IV antenna at 80, 40 m. Built on all HF bands.
Coil L1 is wound on a 40 mm mandrel with a pitch of 2 mm and has 35 turns, a wire with a diameter of 1.2 - 1.5 mm, taps (counting from the ground) - 12, 15, 18, 21, 24, 27, 29, 31, 33, 35 turns.
Coil L2 has 3 turns on a 25 mm mandrel, winding length 25 mm.
Capacitors C1, C2 with Cmax = 160 pF (from the former VHF station).
The built-in SWR meter is used (in FT - 897D)
Inverted Vee antenna on 80 and 40 m - built on all bands.
Yuri Ziborov RZ3GI
Tuner photo:
A great many designs and schemes are known under the name “Z-match”, I would even say more designs than schemes.
The basis of the circuit design from which I based is widely distributed on the Internet and offline literature, it all looks something like this (see right):
And so, looking at many different diagrams, photographs and notes posted on the Internet, the idea was born to me to build an antenna tuner for myself.
My hardware magazine was at hand (yes, yes, I am a follower of the old school - old school, as young people say) and on its page a diagram of a new device for my radio station was born.
I had to remove a page from the magazine “to get to the point”:
It is noticeable that there are significant differences from the original source. I did not use inductive coupling with the antenna with its symmetry; for me, an autotransformer circuit is enough because There are no plans to power the antennas with a balanced line. For ease of setup and monitoring of antenna-feeder structures, I added an SWR meter and a Wattmeter to the overall scheme.
Having finished calculating the circuit elements, you can begin prototyping:
In addition to the housing, it is necessary to manufacture some radio elements; one of the few radio components that a radio amateur can make himself is an inductor:
And here is what happened as a result, inside and outside:
The scales and markings have not yet been applied, the front panel is faceless and not informative, but the main thing is that it WORKS!! And this is good…
R3MAV. info - r3mav.ru
Matching device similar to Alinco EDX-1
I borrowed this antenna matching device circuit from the branded Alinco EDX-1 HF ANTENNA TUNER, which worked with my DX-70.
C1 and C2 300 pf. Air dielectric capacitors. Plate pitch 3 mm. Rotor 20 plates. Stator 19. But you can use dual KPIs with a plastic dielectric from old transistor receivers or with an air dielectric 2x12-495 pf. (as in the picture)
You ask: “Won’t it sew?” The fact is that the coaxial cable is soldered directly to the stator, and this is 50 Ohms, and where should the spark jump with such a low resistance?
It is enough to stretch a line 7-10 cm long from the capacitor with a “bare” wire, and it will burn with a blue flame. To remove static, the capacitors can be bypassed with a 15 kOhm 2 W resistor (quote from “Power amplifiers of the UA3AIC design”).
L1 - 20 turns of silver-plated wire D=2.0 mm, frameless D=20 mm. Bends, counting from the top end according to the diagram:
L2 25 turns, PEL 1.0, wound on two ferrite rings folded together, dimensions D outer = 32 mm, D int = 20 mm.
Thickness of one ring = 6 mm.
(For 3.5 MHz).
L3 has 28 turns, and everything else is the same as L2 (For 1.8 MHz).
But, unfortunately, at that time I could not find suitable rings and did this: I cut rings out of plexiglass and wound wires around them until they were filled. I connected them in series - it turned out to be the equivalent of L2.
On a mandrel with a diameter of 18 mm (you can use a plastic sleeve from a 12-gauge hunting rifle), 36 turns were wound turn to turn - this turned out to be an analogue of L3.
Matching device for delta, square, trapezoid antennas
Among radio amateurs, a loop antenna with a perimeter of 84 m is very popular. It is mainly tuned to the 80M band and with a slight compromise it can be used on all amateur radio bands. This compromise can be accepted if we are working with a tube power amplifier, but if we have a more modern transceiver, things will no longer work there. We need a matching device that sets the SWR on each band, corresponding normal operation transceiver. HA5AG told me about a simple matching device and sent me a short description of it (see picture). The device is designed for loop antennas of almost any shape (delta, square, trapezoid, etc.)
Short description:
The author tested the matching device on an antenna, the shape of which is almost square, installed at a height of 13 m in a horizontal position. The input impedance of this QUAD antenna on the 80 m band is 85 Ohms, and on harmonics it is 150 - 180 Ohms. The characteristic impedance of the supply cable is 50 Ohms. The task was to match this cable with the antenna input impedance of 85 - 180 Ohms. For matching, transformer Tr1 and coil L1 were used.
In the range of 80 m, using relay P1, we short-circuit coil n3. In the cable circuit, coil n2 remains switched on, which, with its inductance, sets the input impedance of the antenna to 50 Ohms. On other bands P1 is disabled. The cable circuit includes n2+n3 coils (6 turns) and the antenna matches 180 Ohms to 50 Ohms.
L1 – extension coil. It will find its application on the 30 m band. The fact is that the third harmonic of the 80 m band does not coincide with the permitted frequency range of the 30 m band. (3 x 3600 KHz = 10800 KHz). Transformer T1 matches the antenna at 10500 KHz, but this is still not enough, you also need to turn on the L1 coil and in this connection the antenna will already resonate at a frequency of 10100 KHz. To do this, using K1, we turn on relay P2, which at the same time opens its normally closed contacts. L1 can also serve in the 80 m range, when we want to work in the telegraph area. On the 80 m band, the antenna resonance band is about 120 kHz. To shift the resonance frequency, you can turn on L1. The switched on coil L1 significantly reduces the SWR and by 24 MHz frequency, as well as on the 10 m band.
The matching device performs three functions:
1. Provides symmetrical power to the antenna, since the antenna web is isolated at HF from the ground through transformer coils Tr1 and L1.
2. Matches the impedance in the manner described above.
3. Using coils n2 and n3 of transformer Tr1, the antenna resonance is placed in the corresponding, permitted frequency bands by range. A little more about this: If the antenna is initially tuned to a frequency of 3600 kHz (without turning on the matching device), then on the 40 m band it will resonate at 7200 kHz, on 20 m at 14400 kHz, and on 10 m at 28800 kHz. This means that the antenna needs to be extended in each range, and at the same time higher frequency range, the more extension it requires. Just such a coincidence is used to match the antenna. Transformer coils n2 and n3, T1 with a certain inductance, the more the antenna extends, the higher the frequency of the range. In this way, on 40 m the coils are extended to a very small extent, but on the 10 m band they are extended to a significant extent. The matching device puts a correctly tuned antenna into resonance on each band in the region of the first 100 kHz frequency.
The positions of switches K1 and K2 by range are indicated in the table (right):
If the input impedance of the antenna on the 80 m range is set not in the range of 80 - 90 Ohms but in the range of 100 - 120 Ohms, then the number of turns of coil n2 of transformer T1 must be increased by 3, and if the resistance is even higher, then by 4. The parameters of the remaining coils remain unchanged changes.
Translation: UT1DA source - (http://ut1da.narod.ru) HA5AG
Elements of the SWR meter: T1 - antenna current transformer wound on a ferrite ring M50VCh2-24 12x5x4 mm. Its winding I is a conductor threaded into a ring with antenna current, winding II is 20 turns of wire in plastic insulation, it is wound evenly around the entire ring. Capacitors C1 and C2 are of the KPK-MN type, SA1 is any toggle switch, PA1 is a 100 μA microammeter, for example, M4248.
Elements of the matching device: coil L1 - 12 turns PEV-2 0.8, internal diameter - 6, length - 18 mm. Capacitor C7 - type KPK-MN, C8 - any ceramic or mica, operating voltage of at least 50 V (for transmitters with a power of no more than 10 W). Switch SA2 - PG2-5-12P1NV.
To set up the SWR meter, its output is disconnected from the matching circuit (in point A) and connected to a 50-ohm resistor (two MLT-2 100 Ohm resistors connected in parallel), and a CB radio station operating for transmission is connected to the input. In the direct wave measurement mode - as shown in Fig. 12.39 position SA1 - the device should show 70...100 µA. (This is for a 4 W transmitter. If it is more powerful, then “100” on the PA1 scale is set differently: by selecting a resistor that shunts PA1 with resistor R5 shorted.)
By switching SA1 to another position (reflected wave control), adjusting C2 achieves zero readings of PA1.
Then the input and output of the SWR meter are swapped (the SWR meter is symmetrical) and this procedure is repeated, setting C1 to the “zero” position.
This completes the adjustment of the SWR meter; its output is connected to the seventh turn of the L1 coil.
The SWR of the antenna path is determined by the formula: SWR = (A1+A2)/(A1-A2), where A1 is the readings of PA1 in the forward wave measurement mode, and A2 is the reverse wave. Although it would be more accurate to talk here not about SWR as such, but about the magnitude and nature of the antenna impedance reduced to the station’s antenna connector, about its difference from the active Ra = 50 Ohm.
The antenna path will be adjusted if by changing the length of the vibrator, counterweights, sometimes the length of the feeder, the inductance of the extension coil (if there is one), etc., the minimum possible SWR is obtained.
Some inaccuracy in antenna tuning can be compensated for by detuning the L1C7C8 circuit. This can be done with capacitor C7 or by changing the inductance of the circuit - for example, by introducing a small carbonyl core into L1.
To match the transceiver with various antennas, you can successfully use a simple hand-held tuner, the diagram of which is shown in the figure. It covers the frequency range from 1.8 to 29 MHz. In addition, this tuner can work as a simple antenna switch, which also has an equivalent load. The power supplied to the tuner depends on the gap between the plates of the variable capacitor C1 used - the larger it is, the better. With a gap of 1.5-2 mm, the tuner could withstand power up to 200 W (maybe more - my TRX did not have enough power for further experiments). You can turn on one of the SWR meters at the tuner input to measure SWR, although this is not necessary when the tuner is working together with imported transceivers - they all have a built-in SWR measurement function (SVR). Two (or more) RF connectors of the PL259 type allow you to connect the antenna selected using the S2 “Antenna Switch” slide switch for operation with the transceiver. The same switch has an “Equivalent” position, in which the transceiver can be connected to an equivalent load with a resistance of 50 Ohms. Using relay switching, you can enable the Bypass mode and the antenna or equivalent (depending on the position of the S2 antenna switch) will be directly connected to the transceiver.
As C1 and C2, standard KPE-2 with an air dielectric of 2x495 pF from industrial household receivers are used. Their sections are threaded through one plate. C1 involves two sections connected in parallel. It is mounted on a 5 mm thick plexiglass plate. In C2 – one section is involved. S1 – biscuits HF switch with 6 positions (2N6P biscuits made of ceramics, their contacts are connected in parallel). S2 - the same, but in three positions (2Н3П, or more positions depending on the number of antenna connectors). Coil L2 - wound with bare copper wire d=1 mm (preferably silver-plated), a total of 31 turns, winding with a small pitch, outer diameter 18 mm, bends from 9 + 9 + 9 + 4 turns. Coil L1 is the same, but 10 turns. The coils are installed mutually perpendicular. L2 can be soldered with leads to the contacts of the biscuit switch by bending the coil into a half ring. The tuner is installed using short thick (d=1.5-2 mm) pieces of bare copper wire. Relay type TKE52PD from the radio station R-130M. Naturally, the best option is the use of higher frequency relays, for example, type REN33. The voltage for powering the relay was obtained from a simple rectifier assembled on a TVK-110L2 transformer and diode bridge KTs402 (KTs405) or similar. The relay is switched by toggle switch S3 “Bypass” type MT-1, installed on the front panel of the tuner. Lamp La (optional) serves as a power-on indicator. It may turn out that in the low frequency ranges there is not enough capacity C2. Then, in parallel with C2, using relay P3 and toggle switch S4, you can connect either its second section or additional capacitors (select 50 - 120 pF - shown in the dotted line in the diagram).
According to the recommendation, the KPI axes are connected to the control handles through sections of durite gas hose, which serve as insulators. To fix them, water clamps d=6 mm were used. The tuner was made in a housing from the Elektronika-Kontur-80 kit. The somewhat larger housing dimensions than the tuner described in leave sufficient scope for improvements and modifications of this circuit. For example, a low-pass filter at the input, a 1:4 matching balun transformer at the output, a built-in SWR meter and others. For the tuner to operate effectively, do not forget about its good grounding.
A simple tuner for tuning a balanced line
The figure shows a diagram of a simple tuner for matching a symmetrical line. An LED is used as a setting indicator.
The material follows the latest description on the Moscow VHF portal. Undoubtedly, it is a respected brand in a non-professional environment, but... any antenna tuner has its own pitfalls.
Actually, only the basics of practical radio engineering will be presented, which are perfectly familiar to military HF radio operators (ours and not ours), as well as the “grandfathers” of amateur radio communications, in which the current generation, spoiled by “coolness” (and sometimes “pseudo-coolness” ") modern technology looks condescendingly; like teenagers against their parents, believing that they understand everything better than their “ancestors,” because it’s a new time. But don’t delude yourself that in the era of “intelligent” technology you don’t need to know anything. For any degree of technological progress will not change the basic laws of physics; and this is as certain as the fact that the sun will not suddenly begin to move from west to east.
Let's get back to the topic.
First and most importantly: if you are working on a stationary antenna in one band, or switching several stationary band antennas with already configured matching elements, forget the word “antenna tuner” in principle and do not read further. You don't need this technique. It applies:
With “random” antennas (a beam of arbitrary length and arbitrary placement in space; especially when operating in a wide frequency range);
With shortened antennas (for example, limited space does not allow the use of the full geometry on the low-frequency bands, and it is not possible to measure the antenna impedance to make a matching circuit);
With single-input multi-band full-size antennas of “tricky” geometry or with ladders (especially horizontal polarization, since the limited height of their suspension greatly affects the input impedance depending on frequency range, the difference of which extends by almost an order of magnitude from 3.5 to 29 MHz)
What does an antenna tuner do physically (either automatic or manual)? And where is its place in the tract? We draw several simple diagrams, from which everything becomes clear without further ado.
Scheme 1, feederless(most often used by field military radio operators in conditions of weak and moderately rough terrain for short-range tactical communications (“lower” HF, unlike VHF, goes around this quite well). Well, in the era of global networks, there is no longer any point in using HF for contacts with the station, abandoned a couple of thousand kilometers into the territory of a potential enemy, as was the case, say, before and during the Second World War.
This circuit - in the case of a structurally inherent wide range of changes in the parameters of the tuner impedance at the output to the antenna (i.e., not only the active R, but also its reactive component) - is capable of matching literally any pieces of wire that will be used as the antenna itself and its counterweight. From the diagram it is clear that the tuner must be a direct continuation of the input/output of the radio station, or be structurally located inside it (which is what is done in field military HF transceivers, take the good old R-107M, even the Codan 2110).
Since there is no feeder on the antenna side of the tuner, it means that the radio itself is in the field, and the antenna most suitable for it is either a vertical or an inclined beam with an arbitrary length, which, when the range changes (i.e. changes the ratio of the length of the antenna wire to the length waves) will need to be adjusted by the tuner at its output to the antenna (since on the side of the tuner facing the radio station there is a constant impedance of the transmitting-receiving path). In such antennas, the metal body of the radio itself and its capacitive (less often through a ground electrode) connection to the ground are often used as a counterweight. We see: well, this is not an amateur radio option “for home”, and even more so - it is of little use for DX in urban conditions: the radio station will have to be placed near a window, the antenna beam should be output through its frame and the “artificial earth” connected to the bathtub ground electrode.
Scheme 2, with a feeder from the radio station to the tuner.
Such a connection assumes that the constant resistance of the output of the transceiver path (most often a 50 Ohm coaxial output) is loaded onto a feeder of arbitrary length with the same characteristic impedance, and the tuner input must also be configured to this value. Then the SWR between the output of the transceiver and the input of the tuner will be equal to one. That is, upon transmission, all the power of the transmitter will go to the tuner, and upon reception, the receiver will receive all the power from the tuner (of course, with the exception of linear losses in the feeder, the greater the longer its length and the smaller its diameter, the greater). Since the circuit operates only with a feeder from the radio station to the tuner, this implies a direct connection of the second side of the tuner with what we will use as an antenna and its counterweight. These can already be dipoles, and rhombuses, and... Yes, whatever your heart desires; at least for anti-aircraft communications over a couple of hundred kilometers, at least for contacts with the other hemisphere! However, it also follows that you can only install a radio station in the room, but not a tuner (it is directly on the antenna!). And this in turn means that the tuner in the following scheme:
Must be street compatible;
Be automatic (if you plan to work on different bands; you can’t adjust it to the mast every time!);
- have a power line for the automation drives to the room or built-in batteries (the latter is not very good either in winter or if the antenna elements are placed on a high mast).
In general, we again have a not very amateur radio option (although it is the best), considering that good “street” tuners are also priced like half a transceiver, because Even the simplest “intelligent” automation, high-quality drives for setting it up and a reliably sealed case are very expensive.
The third scheme remains, purely “amateur radio”. But it is precisely the one that is very often used incorrectly, causing the old men Hertz and Popov to probably turn over in their resting places.
Scheme 3, with a feeder from the tuner to the antenna. It also involves a short cable connector from the tuner to the transceiver, which does not cause any trouble, as we saw from the consideration of diagram 2.
Let's go to the antenna side of the tuner and see what we will have when connecting the tuner and antenna with a coaxial cable arbitrary length.
Let us immediately remember: a coax of arbitrary length works as a purely ohmic transmission line only with antennas tuned to resonance (i.e., having purely active resistance in theory, or minimal reactivity in practice). If we have a "random" antenna with an impedance that is far from the net activity at the operating frequency, a cable of arbitrary length becomes long line, far from purely ohmic. And the tuner perceives this “cable + antenna” complex as a load, tuning it to deliver maximum power from the transmitter. What will be emitted into the air by the antenna component of this complex - only God knows!
This is where the main mistake of using “home” antenna tuners lies.
To avoid it, we again recall the theory of transmission lines and discover one remarkable feature: the supply line with a length that is a multiple of a half-wave has an impedance close to infinity (Fig. 3). It is from this, by the way, that it follows that it can be used with absolutely any (!) own characteristic impedance. Those. when connecting the antenna to the tuner via such a line, it’s as if we don’t have it!
Having calculated such a line with a length of L/2, for example, from a coaxial (at least 50, at least 75 Ohms; do not forget about the shortening coefficient in the dielectric) for the range of 3.5 MHz (this, with a shortening coefficient in polyethylene of 0.66 for half a wave, will be 28 .3 m is enough even for masts of decent height), we will get its remarkable property of “infinite” impedance (zero shunting of the passing signal, if you want) at frequencies 7; 10.5; 14; 17.5; 21; 24.5 and 28 MHz. Do you recognize a familiar row? Although somewhat worse, it is still close even for the WARC ranges. And this property of the line at the indicated frequencies does not change any impedance of the antenna. That is, the tuner will be tuned to deliver maximum power to it, simply “without seeing” the cable, which is what we need. And at the same time, the tuner can be located next to the transceiver, and not on the antenna, allowing its comfortable “sofa” tuning.
I can’t ignore the nuances of our “magic” feeder. There are two of them. First: use a thick cable (RG -213, 8D -FB, 10D -FB), because otherwise its linear attenuation at “high” ranges will be very significant.
The second is related to its configuration. It should be carried out for the highest frequency range with the maximum number of half-waves in length (then it will be automatically tuned to lower frequency ranges). In practice, the author, using MFJ antenna analyzers, discovered a very sharp tuning to the maximum SWR of a closed half-wave line at the operating frequency (Fig. 4). It is enough to simply shorten and shorten a obviously longer section of cable little by little until a sharp peak of high SWR (under 10 or more) at the device generator frequency of 28.4...28.5 MHz. This does not harm the device.
Last point: a great many antenna tuners are built according to a T- or U-shaped scheme of a matching L 2C link. For this very reason, any adjustment of the “manual” tuner on one side always entails some detuning of the previously tuned other side. So operating such a device requires some practice.