VHF or antenna dual / triple square earth
In 1959, the epochal article of Sergey Kuzmich Sotnikova, an enthusiast of long-distance television reception, was published in the fourth issue of Radio magazine about the use of dual and triple square antennas for long-distance television reception on MW (and later on the UHF).
The declared phenomenal characteristics of 10–12 dBi for a double square and 16–17 dBi for a triple square excited the minds of the Soviet amateur radio community and for many decades predetermined the tremendous success of such antennas on CF and UHF: the descriptions of these antennas wandered from book to book, from magazine to magazine . Thousands of Soviet citizens repeated them.
Although these characteristics are greatly exaggerated, they were still based on the publications of reputable researchers: Sam Leslie (W5DQV, 1955 publication), Dick Bird (G4ZU), Rothammel (with reference to Leslie and Bird).
In 1962, Vladimir Pavlovich Sheiko-Vvedensky (UB5CI) published a book “Antennas of amateur radio stations” in the publishing house DOSAAF where there are also references to 13 dBi from a double square.
A large abundance of authoritative sources determined that Sotnikov’s incorrect conclusions were popular even in 2018.
Let's try to figure out where the truth here borders on a hoax
In the book of Rothammel (translation Krenkel 1967) considered HF antennas of 20, 15 and 10 meters (14, 21 and 30 MHz).
Referring to Sam Amateur Leslie (Oklahoma, W5DQV, publishing the results of extensive experiments with 1955 squares), and Dick Byrd (G4ZU, England), the dual square antennas in these bands have a directivity of 10 to 13 dBi (8 to 11 dBd)
Simulation in 4NEC2 with the ground (Sommerfeld-Norton real earth mode) fully confirms these observations: with a moderate conductance of earth, you can get 12.4 dBi, and with a perfect conductor of 13.8 dBi with an antenna suspension height of 1λ.
It should be noted that in the experiments of Leslie and Byrd, the dBd measurement was not made relative to the actually constructed dipole, but by measuring the field strength at a certain distance, at a known power in the TX antenna and comparing the measured intensity with the calculated by Friis formula.
The fact is that the usual Hertz dipole, which has 2.13 dBi, with a suspension height of 1λ per HF, forms a double-lobe DN with a maximum of 8.2 dBi. Those. the dipole itself at the expense of the earth takes precedence over 6.1 dBd
. Leslie and Byrd's measurements are relative to an imaginary 2.13 dBi dipole, rather than alternately switching the “double square” antenna and the dipole.
The 2-element wave channel (reflector + vibrator) also has a practically identical “double square” radiation pattern: 11.8 dBi at the antenna suspension height of 1λ with moderate earth conductivity. The shape of the main and 3 side lobes is almost identical to the DN of a double square.
Since there are no antennas in HF in free space, the methodology and the obtained data are completely relevant and have practical application. Measurement of these antennas in free space on HF is impossible.
Simulation in 4NEC2 gives 7.73 dBi for a double square and 6.95 dBi for a 2-element wave channel.
In 1962, in the DOSAAF publishing house, a radio amateur from Kharkov, Vladimir Pavlovich Sheiko-Vvedensky (UB5CI) publishes the book “Antennas of Amateur Radio Stations”. In this antenna "double square" are described in the chapter "HF antenna". Sheiko gives a completely correct description of the principle of operation - “a system of two anti-phase excited quarter-wave horizontal emitters”.
The sizes and methods of power supply for the ranges of 20, 15 and 10 meters (14, 21 and 30 MHz) are given.
In the chapter “VHF antennas” Sheyko mentions such antennas, although he does not recommend them. Sheiko says about the directional properties: “The following data on the gain of frame antennas is known: a double square - 9-11 dB (8-13 times), a triple square 14-15 dB (25-32 times).
If these data are given for free space, then they contradict the data in the previous chapter on HF antennas, because there will be much more with the ground. If these data are given taking into account the earth (extrapolating the directivity to HF), then the ground does not work on VHF as an endless flat conductor, as described in detail in Goncharenko’s book “ Chapter 12.1.2 Land on VHF ”
In the same way as Sheiko, three years earlier in 1959 went enthusiast Sergei Sotnikov.
In order to somehow explain the incredible directionality of such a simple antenna, Sotnikov hypothesized that the frame vibrator has 4 working elements and it is equivalent to a 2-storey HEADLIGHT of 2-element wave channels.
But the 2-storey HEADLIGHT is excited in phase - on each floor the direction of the currents is the same. In the frame antenna, on different floors, currents flow in antiphase, this is described in the book of Rothammel and Sheiko, and follows from simple conclusions - the length of the horizontal and vertical parts of each arm is λ / 2, so the current flows in antiphase on the upper floor.
The frame vibrator with a 1λ perimeter has a close to isotropic directivity, with a slight gain perpendicular to the plane and a slight attenuation to the sides. Depending on the shape of such a frame, its wave resistance changes significantly and the directionality varies very slightly.
If the frame is as wide as possible and has a minimum height - we get a Pistolkors half-wave loop vibrator. Its resistance is as close as possible to 300 ohms, and the exact value depends on the diameters of the upper and lower tubes. The directivity is 2.13 dBi, as in the split Hertz dipole.
With a decrease in the width of the loop and an increase in height, the resistance Ra decreases, and the shape of the DN varies very little. If the width tends to zero, and the height to λ / 2, we get a transmission line with a length of λ / 2 short-circuited at the end. Ra such line is 0.
Depending on the ratio of height / width and shape of the frame - Ra can be obtained from 0 to 300 Ohms. With a square frame with λ / 4 side length, the resistance is about 135-140 ohms, and the bottom has a maximum forward / backward of 3.48 dBi (1.35 dBd). Any other shapes are possible - round frame, triangular, “dumbbell”, “parachute” and even irregular shapes.
There are almost no electrical advantages of one form or another. A frame with a smaller width has a constructive advantage - it is more mechanically durable with a smaller conductor cross section than the Pistolcors vibrator. At HF it is possible to make squares of thin flexible wire, pulling them on a cross-shaped struts. It is precisely the mechanical advantages and low cost that determined the popularity of squares in shortcars compared to wave channels, which have very similar electrical characteristics, but require high-power pipes + traverse + stretching to maintain long pipes.
In addition to repeatedly overestimated data on the directivity of squares on VHF, Sotnikov gives incorrect data both in size (a very large slip in resonance) and in radiation resistance and matching.
In the sizes given for the 12th MW channel (222-230 MHz) from a 6 mm bar, the resonance occurs at a frequency of 242 MHz (HFSS) and 245 MHz (4NEC2). Ra = 150 ohms and 167 ohms, respectively.
To connect such an antenna to the 75 Ohm transmission line, it is necessary to manufacture a balancing matching device (SSU, balun) 2: 1. When connected through a 1: 1 balun, even at the resonant frequency, the CWS cannot be less than 2. At frequencies below the resonant, Ra drops sharply and negative (capacitive) reactivity increases.
At a frequency of 222 MHz, the CWS75 = 6.8 (NEC2) or CWS75 = 8 (HFSS).
Ku at the resonant frequency of 7.19 dBi (HFSS) and 6.67 dBi (NEC2). The shape of the main and side lobes in different programs is almost identical.
At the request of the user REPISOT, we will analyze the possibility of using square antennas for the decimeter range of television broadcasting.
Such an antenna is manufactured industrially under the brand name “Signal 3.0”. The declared range for SWR <1.5 is 470-862 MHz, gain up to 14 dB (16 dBi ??)
Let's perform a simplified simulation in HFSS (without plastic spacers and without rounding the corners, this will slightly shift the resonant frequency, but we are not interested in the exact value now) . The director frame has a gap of 1 mm.
As expected, the antenna has a single resonance (at about 626 MHz), Ra = 150 ohms. When powering through a 2: 1 SSU to a 75 Ohm cable, you can get a CWS = 1 on this channel (approximately 40th channel), and a CWS <2 will be in the range of 562-737 MHz.
From the bottom, like all squares, the reactivity is gained very quickly, and Ra drops very quickly too. KSV150> 6 already at 535 MHz, and at 470 MHz KSV150 = 35
Directivity at a resonant frequency of 6.88 dBi, F / B = 12.77 dB It is
extremely difficult to manufacture an SSH 2: 1 at UHF, therefore the manufacturer did not even try.
The antenna is completed with a printed equivalent of a half-wave loop, which works as a 4: 1 transformer, but only when the electrical length of the loop is L / 2. Such an SSU is, by definition, narrowband (single-channel). With a load of 75 Ohms, the input resistance of such SSU is 300 Ohms. But the manufacturer equipped the antenna with a 50 Ohm cable (although the TVs and tuners are all 75 Ohms). Perhaps the manufacturer considered that 200 is closer to 150 than 300, and in order to reduce reflection on the border, the antenna <-> cable donated an additional reflection on the border of the cable <-> TV.
With a load of 300 ohms (symmetrization boards or SWA / PAE / ALN amplifiers), the antenna has a SWR of about 2 in the 616-750 MHz range.
With a load of 75 Ohms (a quarter-wave transformer, as in Sotnikov's circuits), the antenna is strongly mismatched everywhere, but in a narrow section of 577-608 MHz, the CWS drops to 2.
The radiation directivity forwards at 6.7 dBi antenna retains from 540 to 860 MHz.
At a frequency of 500 MHz, F / B drops to 0 (and is radiated forward and backward at 5.2 dBi)
Such an antenna, by complexity, exceeds the 3-wave Wave-1 wave channel with a retail value of $ 3.5
A and by electrical characteristics loses much
The declared phenomenal characteristics of 10–12 dBi for a double square and 16–17 dBi for a triple square excited the minds of the Soviet amateur radio community and for many decades predetermined the tremendous success of such antennas on CF and UHF: the descriptions of these antennas wandered from book to book, from magazine to magazine . Thousands of Soviet citizens repeated them.
Although these characteristics are greatly exaggerated, they were still based on the publications of reputable researchers: Sam Leslie (W5DQV, 1955 publication), Dick Bird (G4ZU), Rothammel (with reference to Leslie and Bird).
In 1962, Vladimir Pavlovich Sheiko-Vvedensky (UB5CI) published a book “Antennas of amateur radio stations” in the publishing house DOSAAF where there are also references to 13 dBi from a double square.
A large abundance of authoritative sources determined that Sotnikov’s incorrect conclusions were popular even in 2018.
Let's try to figure out where the truth here borders on a hoax
In the book of Rothammel (translation Krenkel 1967) considered HF antennas of 20, 15 and 10 meters (14, 21 and 30 MHz).
Referring to Sam Amateur Leslie (Oklahoma, W5DQV, publishing the results of extensive experiments with 1955 squares), and Dick Byrd (G4ZU, England), the dual square antennas in these bands have a directivity of 10 to 13 dBi (8 to 11 dBd)
Simulation in 4NEC2 with the ground (Sommerfeld-Norton real earth mode) fully confirms these observations: with a moderate conductance of earth, you can get 12.4 dBi, and with a perfect conductor of 13.8 dBi with an antenna suspension height of 1λ.
It should be noted that in the experiments of Leslie and Byrd, the dBd measurement was not made relative to the actually constructed dipole, but by measuring the field strength at a certain distance, at a known power in the TX antenna and comparing the measured intensity with the calculated by Friis formula.
The fact is that the usual Hertz dipole, which has 2.13 dBi, with a suspension height of 1λ per HF, forms a double-lobe DN with a maximum of 8.2 dBi. Those. the dipole itself at the expense of the earth takes precedence over 6.1 dBd
. Leslie and Byrd's measurements are relative to an imaginary 2.13 dBi dipole, rather than alternately switching the “double square” antenna and the dipole.
The 2-element wave channel (reflector + vibrator) also has a practically identical “double square” radiation pattern: 11.8 dBi at the antenna suspension height of 1λ with moderate earth conductivity. The shape of the main and 3 side lobes is almost identical to the DN of a double square.
Since there are no antennas in HF in free space, the methodology and the obtained data are completely relevant and have practical application. Measurement of these antennas in free space on HF is impossible.
Simulation in 4NEC2 gives 7.73 dBi for a double square and 6.95 dBi for a 2-element wave channel.
In 1962, in the DOSAAF publishing house, a radio amateur from Kharkov, Vladimir Pavlovich Sheiko-Vvedensky (UB5CI) publishes the book “Antennas of Amateur Radio Stations”. In this antenna "double square" are described in the chapter "HF antenna". Sheiko gives a completely correct description of the principle of operation - “a system of two anti-phase excited quarter-wave horizontal emitters”.
The sizes and methods of power supply for the ranges of 20, 15 and 10 meters (14, 21 and 30 MHz) are given.
In the chapter “VHF antennas” Sheyko mentions such antennas, although he does not recommend them. Sheiko says about the directional properties: “The following data on the gain of frame antennas is known: a double square - 9-11 dB (8-13 times), a triple square 14-15 dB (25-32 times).
If these data are given for free space, then they contradict the data in the previous chapter on HF antennas, because there will be much more with the ground. If these data are given taking into account the earth (extrapolating the directivity to HF), then the ground does not work on VHF as an endless flat conductor, as described in detail in Goncharenko’s book “ Chapter 12.1.2 Land on VHF ”
In the same way as Sheiko, three years earlier in 1959 went enthusiast Sergei Sotnikov.
In order to somehow explain the incredible directionality of such a simple antenna, Sotnikov hypothesized that the frame vibrator has 4 working elements and it is equivalent to a 2-storey HEADLIGHT of 2-element wave channels.
But the 2-storey HEADLIGHT is excited in phase - on each floor the direction of the currents is the same. In the frame antenna, on different floors, currents flow in antiphase, this is described in the book of Rothammel and Sheiko, and follows from simple conclusions - the length of the horizontal and vertical parts of each arm is λ / 2, so the current flows in antiphase on the upper floor.
The frame vibrator with a 1λ perimeter has a close to isotropic directivity, with a slight gain perpendicular to the plane and a slight attenuation to the sides. Depending on the shape of such a frame, its wave resistance changes significantly and the directionality varies very slightly.
If the frame is as wide as possible and has a minimum height - we get a Pistolkors half-wave loop vibrator. Its resistance is as close as possible to 300 ohms, and the exact value depends on the diameters of the upper and lower tubes. The directivity is 2.13 dBi, as in the split Hertz dipole.
With a decrease in the width of the loop and an increase in height, the resistance Ra decreases, and the shape of the DN varies very little. If the width tends to zero, and the height to λ / 2, we get a transmission line with a length of λ / 2 short-circuited at the end. Ra such line is 0.
Depending on the ratio of height / width and shape of the frame - Ra can be obtained from 0 to 300 Ohms. With a square frame with λ / 4 side length, the resistance is about 135-140 ohms, and the bottom has a maximum forward / backward of 3.48 dBi (1.35 dBd). Any other shapes are possible - round frame, triangular, “dumbbell”, “parachute” and even irregular shapes.
There are almost no electrical advantages of one form or another. A frame with a smaller width has a constructive advantage - it is more mechanically durable with a smaller conductor cross section than the Pistolcors vibrator. At HF it is possible to make squares of thin flexible wire, pulling them on a cross-shaped struts. It is precisely the mechanical advantages and low cost that determined the popularity of squares in shortcars compared to wave channels, which have very similar electrical characteristics, but require high-power pipes + traverse + stretching to maintain long pipes.
In addition to repeatedly overestimated data on the directivity of squares on VHF, Sotnikov gives incorrect data both in size (a very large slip in resonance) and in radiation resistance and matching.
In the sizes given for the 12th MW channel (222-230 MHz) from a 6 mm bar, the resonance occurs at a frequency of 242 MHz (HFSS) and 245 MHz (4NEC2). Ra = 150 ohms and 167 ohms, respectively.
To connect such an antenna to the 75 Ohm transmission line, it is necessary to manufacture a balancing matching device (SSU, balun) 2: 1. When connected through a 1: 1 balun, even at the resonant frequency, the CWS cannot be less than 2. At frequencies below the resonant, Ra drops sharply and negative (capacitive) reactivity increases.
At a frequency of 222 MHz, the CWS75 = 6.8 (NEC2) or CWS75 = 8 (HFSS).
Ku at the resonant frequency of 7.19 dBi (HFSS) and 6.67 dBi (NEC2). The shape of the main and side lobes in different programs is almost identical.
Simulation results for the 12th MV channel in HFSS and 4NEC2
findings
- Frame vibrator with a perimeter of 1λ of any shape forms a close to isotropic radiation pattern. There is a small gain perpendicular to the plane of the frame - for a half-wave loop equal to 2.13 dBi, and for a square frame about 3.5 dBi.
- When adding a reflector to the frame, its directivity can be increased to 6.95 dBi for a 2-element wave channel or to 7.73 dBi for a double square.
- At frequencies below 50 MHz, the placement of any antenna at a small height above the ground (in lambda units) greatly changes the resulting DN. 2.13 dBi dipole turns into 8.2 dBi, 6.95 dBi wave channel turns into 11.8 dBi, 7.73 dBi double square turns into 12.4 dBi.
- The directivity data described by Leslie, Bird, Rothammel and Sheiko refer to low-suspended antennas, which include almost all HF antennas.
- Sergey Sotnikov extrapolated the performance of HF antennas to a double square on VHF, why it cannot be done - it is written in the “Chapter 12.1.2 Land on VHF” of the book by Goncharenko.
- To substantiate such a huge focus of squares - Sotnikov radically rewrote the principle of the square, comparing it with a 2-storey HEADLIGHTS of half-wave dipoles and wave channels.
- The real directivity of the dual and triple square antennas slightly (less than 1 dB) exceeds the directivity of 2 and 3-element wave channels.
- The characteristic impedance of the double square (with a spacing of 0.15λ) is close to 150 ohms. For operation at 75 ohms, a 2: 1 SSA is required, and for 50 ohms, a 3: 1 SSA is required. When operating through a 1: 1 CCS, the CWS cannot be <2 at the resonant frequency.
- The dimensions of the antennas given Sotnikovym calculated with a significant slip on the resonance and the minimum CWS. So the antenna for the 222-230 MHz range has a resonance of about 242-245 MHz, and on its calculated range, the VSWR exceeds 7-8.
- If we omit the overestimation of 10-11 dBi, the antenna can be quite working (when deciding on the matching issue), 6.7 dBi on VHF for television is quite a decent gain.
- The directivity of the double square does not correspond to the 5-element wave channel. The industrially produced Uda-Yagi antenna for channel 6-12 (2-pipe reflector, loop vibrator, 4 directors) with a length of 1.35 meters gave a gain of 8.6 dBi at 174 MHz to 10.9 dBi at 230 MHz and a simple 75 ohm matching. Narrowband (single-channel) Yuda-Yagi with equal length or equal number of elements will have even higher gain.
Triple square on dmv tv (dvb-t2)
At the request of the user REPISOT, we will analyze the possibility of using square antennas for the decimeter range of television broadcasting.
Such an antenna is manufactured industrially under the brand name “Signal 3.0”. The declared range for SWR <1.5 is 470-862 MHz, gain up to 14 dB (16 dBi ??)
Let's perform a simplified simulation in HFSS (without plastic spacers and without rounding the corners, this will slightly shift the resonant frequency, but we are not interested in the exact value now) . The director frame has a gap of 1 mm.
As expected, the antenna has a single resonance (at about 626 MHz), Ra = 150 ohms. When powering through a 2: 1 SSU to a 75 Ohm cable, you can get a CWS = 1 on this channel (approximately 40th channel), and a CWS <2 will be in the range of 562-737 MHz.
From the bottom, like all squares, the reactivity is gained very quickly, and Ra drops very quickly too. KSV150> 6 already at 535 MHz, and at 470 MHz KSV150 = 35
Directivity at a resonant frequency of 6.88 dBi, F / B = 12.77 dB It is
extremely difficult to manufacture an SSH 2: 1 at UHF, therefore the manufacturer did not even try.
The antenna is completed with a printed equivalent of a half-wave loop, which works as a 4: 1 transformer, but only when the electrical length of the loop is L / 2. Such an SSU is, by definition, narrowband (single-channel). With a load of 75 Ohms, the input resistance of such SSU is 300 Ohms. But the manufacturer equipped the antenna with a 50 Ohm cable (although the TVs and tuners are all 75 Ohms). Perhaps the manufacturer considered that 200 is closer to 150 than 300, and in order to reduce reflection on the border, the antenna <-> cable donated an additional reflection on the border of the cable <-> TV.
With a load of 300 ohms (symmetrization boards or SWA / PAE / ALN amplifiers), the antenna has a SWR of about 2 in the 616-750 MHz range.
With a load of 75 Ohms (a quarter-wave transformer, as in Sotnikov's circuits), the antenna is strongly mismatched everywhere, but in a narrow section of 577-608 MHz, the CWS drops to 2.
The radiation directivity forwards at 6.7 dBi antenna retains from 540 to 860 MHz.
At a frequency of 500 MHz, F / B drops to 0 (and is radiated forward and backward at 5.2 dBi)
Such an antenna, by complexity, exceeds the 3-wave Wave-1 wave channel with a retail value of $ 3.5
A and by electrical characteristics loses much