This antenna has long and deservedly been popular among radio amateurs. Its design is simple, it is easy to set up and is consistent with a feeder with any characteristic impedance. However, its large dimensions (total length is 0.75λ) make it difficult to use on HF bands. But in the VHF bands it is used quite often.
Rice. 1. Antenna design sketch
The antenna (Fig. 1) is a vibrator with a length of λ/2, powered from the end through a matching device made in the form of a quarter-wave open line, closed at the lower end. The high input impedance of a half-wave vibrator when fed from the end (several kilo-ohms) is easily transformed to the characteristic impedance of the cable by choosing the optimal distance from the power points (X1, X2) to the closed end of the line. Using an open line as a transformer ensures low losses at high transformation ratios. The J-antenna gain is +0.25 dBd, which is slightly higher than the dipole gain (due to the two-wire line).
The vertical J-antenna, due to incomplete symmetry, has a small radiation with horizontal polarization (Fig. 2).
Rice. 2. Parameters and radiation pattern
We modify the J-antenna by bending the quarter-wave line by 90 degrees (Fig. 3). With a bit of sizing adjustment, it is not difficult to achieve good matching and 0 dBd gain. However, with this version of the antenna, a noticeable part of the radiation is already horizontally polarized. It is caused by a common-mode current in a two-wire line, which plays the role of a counterweight (current collector) in the J-antenna.
Rice. 3. Modified antenna design
Let's add another half-wave vibrator, connecting it to the free end of the two-wire line (Fig. 4). We obtain a completely symmetrical structure in the vertical plane. There is no common-mode current in a two-wire line, as well as radiation with horizontal polarization. This option is a collinear antenna of two half-wave vibrators fed through a quarter-wave line closed at the end.
Rice. 4. Modified antenna design
Such an antenna is described by SM0VPO on his website in the article “6 dB collinear VHF antenna by Harry Lythall - SM0VPO”. Its gain (about 2.4 dBd) is obtained by narrowing the radiation pattern in the vertical plane. In the horizontal plane, the radiation diagram is circular. The antenna is structurally very simple and can be made from one piece of aluminum rod or tube. To maintain the symmetry of the antenna, it is advisable to connect the power cable through a balun transformer. SM0VPO uses a U-elbow balun transformer. You can limit yourself to a few ferrite rings placed on the cable near the antenna feed point.
Let's call this design a Super-J antenna for short. What further modification is possible?
Rice. 5. Modified antenna design
By adding reflectors to the design, we get a two-element Super-J antenna (Fig. 5). This is already a directional collinear antenna with a gain of +5.8 dBd. And if we add directors, we get a three-element Super-J antenna (Fig. 6) with a gain of +8 dBd (Fig. 7). An attempt to add a second director gives an increase in gain of only 0.8 dB, but noticeably increases the length of the antenna...
Rice. 6. Modified antenna design
Rice. 7. Parameters and radiation pattern
What is the advantage of these antennas over multi-element Yagi?
With the same area, their gains are approximately equal, but the advantages of Super-J antennas are the short boom length, the associated small turning radius and ease of matching. The disadvantages include the need to use a dielectric mast, at least its upper part.
In Fig. Figure 8 shows a photograph of a three-element Super-J antenna for the 144 MHz range, made of aluminum rod with a diameter of 8 mm.
Rice. 8. Three-element Super-J antenna for 144 MHz band
A dielectric mast (for example, fiberglass) and an insulating spacer are located in the spaces between the elements. In Fig. 9 they are shown with thicker lines. It is better to route the power cable horizontally behind the reflectors and return it to the mast in a wide loop, away from the ends of the reflector. In this area (near the antenna), it is advisable to put tubular ferrite magnetic cores (from the monitor power cables) on the cable every 0.5 m.
Rice. 9. Antenna design
A similar three-element Super-J antenna can be made for the 430 MHz range. In the table and in Fig. 10 shows the required design dimensions for frequencies of 145 and 435 MHz. The dimensions of the elements and the distance between their axes are indicated in centimeters (D is the diameter of the aluminum or copper conductors from which the antenna is made). Input impedance at the power point is 50 or 200 ohms. If a U-elbow is used for balancing, it transforms the feeder resistance to 200 ohms, so the connection point to the two-wire line will be slightly further from the closed end. In this case, the dimensions of the matching loop change slightly (see table).
Rice. 10. Structural dimensions
Table
| Frequency, MHz | R inx, Ohm | ||||||||||
The sizes of elements marked with an asterisk are specified during setup.
For ease of setup, it is recommended that the matching device be made with two movable contacts (sliders): one, closing the two-wire line, is used for tuning to resonance, the second, connecting the feeder, is used for matching to the minimum SWR level. This allows you to quickly configure the antenna, but after selecting the positions of the slides, you must ensure reliable contact (by soldering or bolts). The efficiency of the antenna greatly depends on the contact resistance. It is worth remembering that copper-aluminum contact is inadmissible and that the contact is protected from moisture. On the contrary, the requirements for contact resistance at the open end of the J-elbow are not strict, since the current there is minimal.
Initially, the antenna was made according to Fig. 4 at an average frequency of 145 MHz from an aluminum rod with a diameter of 8 mm. It was attached to a fiberglass pipe with a diameter of 23 mm, used as a mast. A ferrite tube placed on the cable near the antenna feed point was used as a balun. Her tests showed that when the antenna is placed on a wooden table parallel to the ground and when it is positioned vertically, the settings do not match. Therefore, the antenna must be tuned by installing it vertically. It is enough that the distance from the lower ends of the vibrators to the ground is about 0.5 m. By moving the shorting jumper along the two-wire loop and moving the cable connection points (these adjustments are interdependent), it was quite easy to match the antenna to SWR
Then booms, also made of aluminum rod with a diameter of 8 mm, were attached to the mast and active vibrators, since there were no dielectric tubes of the required rigidity on hand. At the midpoint of the vibrators, the voltage is close to zero, so the conductive boom has little effect on the antenna characteristics, which was confirmed by preliminary modeling.
Reflectors and directors were installed on the booms, the lengths of which were calculated according to the model calculation using the MMANA program. The two-wire line and booms are fixed to the mast using 10 mm thick vinyl plastic plates and U-shaped brackets. The antenna elements are attached to the booms using duralumin U-shaped brackets and bolts.
Passive elements sharply reduced the antenna's input impedance. However, a weakly expressed SWR minimum was found. By moving the jumper and shifting the cable connection points, we found a position where the minimum SWR corresponded to a frequency of 145 MHz and did not exceed 1.2. The lengths of the vibrators were not adjustable.
Compared to tuning a single-element antenna, tuning a three-element antenna is much more acute and critical. Band by SWR level
The performance of the antenna was previously assessed in urban conditions (among tall buildings that completely covered the horizon) with its axis located above the ground at a height of only 1.5 m. Compared to a quarter-wave automobile rod, it gave a signal increase of 2... 3 points for communications on distances of 10...50 km. The directionality in the horizontal plane was clearly pronounced. The general impression is that the antenna works. More accurate assessments of the performance of the Super-J antenna were made in open areas in dacha conditions when the antenna was lifted onto a mast 7 m high. Its performance was compared with the performance of a four-element “square” antenna with vertical polarization. The antennas were installed alternately on the same fiberglass mast in the same place. The same cable as a feeder and the same transceiver were used. The work on the opening and audibility of repeaters located at distances from 30 to 100 km and the assessments of correspondents when conducting QSOs in the direct channel at distances of up to 70 km were assessed.
In most cases the estimates were very close. If you've heard "square", you've also heard Super-J. The four-element “square” had a narrower radiation pattern in the horizontal plane, so it had to be aimed more accurately at the correspondent to get maximum rating; the Super-J was almost not turned. The general impression is that the antennas have approximately equal gains and good back-lobe suppression. The antenna under test is two times lighter than the “squares” and has a significantly lower torque and windage.
The idea to use improvised means in the manufacture of “field and camping antennas” at 145 and 50 MHz came while on vacation in the Crimea, in the mountains near the village of Ordzhonikidze. As always, the 8-10th day of sailing at sea becomes critical for me, and my gaze almost always stops at the nearby hills and high-rise buildings like Kara-Dag, of which there are a decent number in the area of the “Dvuyakornaya” bay. The time of “closed places” has passed, and wandering around these hills 200-350 meters high is a pleasure (if you have an FT-817 YAESU hanging around your neck). Everything is wonderful and good even with a standard “elastic band”, but if there is a connection for 200 km, then you always want to have it for 400 km, but if you connect the Sporadic to 50 MHz, then it is best to look at the sea from the mountain.
For this, of course, it is advisable to have a full-size antenna, at least a dipole. The simplest vertical dipole is the 300 ohm ribbon cable J antenna, which was described by Bob Orr (W6SAI) and is still popular today. But the question arises: where can I find such a cable now? After all, if you remember, it was used 30-35 years ago as a VHF antenna for the first broadcast stationary FM receivers.
The J-antenna circuit is shown in Fig. 1, where: A is a short-circuited quarter-wave matching loop, BA is a half-wave emitter, C is the distance from the short-circuited end of the loop to the connection point of the 50-ohm coaxial feeder. Antenna dimensions can be calculated for any range using the formulas: B(cm)=21502/F(MHz), A(cm)=7132/F(MHz), C(cm)=571/F(MHz). For example, for 145 MHz - B = 148 cm, A = 49.2 cm, C = 4.6 cm, and for 50 MHz - B = 430.1 cm, A = 142.8 cm, C = 13.4 cm .
Anyone can make and configure such an antenna in 1...1.5 hours. To do this, you need to have an installation wire with a cross-section of 1.5 mm2 or more in PVC insulation and a sufficient number of plastic cards, for example, from telephone booths. Spacers in the form of 30x30 mm squares are cut out of plastic cards (Fig. 2), in the corners of which holes are drilled according to the diameter of the wire.
The number of such squares is prepared at the rate of 2 pieces. by 10 cm of the length of line A. A piece of length A + B + 25 mm is cut from the wire and the antenna is assembled, as shown in Fig. 3. At a distance C from the short-circuited end, the insulation on A and B is removed and the 50-ohm cable is soldered. The wire on all spacers and the cable on the first spacer near the short-circuited end are fixed “crosswise” with PVC electrical tape. This completes the main installation work.
Settings
The given formulas for antenna sizes do not take into account shortening in the case of using a wire with PVC insulation, therefore, for example, when manufacturing a 50 MHz antenna, its dimensions are 2-4 cm longer than necessary. But this is good, because... It is possible to very accurately adjust the antenna using ordinary wire cutters.
The author usually uses RG-58 as a feeder for traveling conditions, but fluoroplastic RK-50 is also suitable. With a 75-ohm cable, you won't get better than 1.2 SWR unless you increase size C by 3-4%.
When first turned on, the antenna was always longer and was built at 48.5-49 MHz with an SWR of 1.8-2.5 and increased Rbx. This was confirmed in the manufacture of several antennas. To lower the input impedance to 50 Ohms, it was enough to shorten size A by 3-6 cm, and only then adjust size B to the required resonant frequency (in this case, 50.110 MHz). The same picture was observed with the antenna at 145.3 MHz. If suddenly the wrong wire is used and with a different insulation :) or even bi-metallic wire is used instead of copper wire, and fiberglass plates are used instead of cards, then Rbx may be below 50 Ohms. In this case, you will have to lengthen size A a little, and only then adjust size B.
Well, then it’s even easier. A rod made of bamboo or fiberglass of appropriate length is taken (or made up of several rods), which acts as a supporting mast. The end of the J-antenna emitter is attached to its top by the insulator, and this structure rises vertically. They were almost always on a “two” with such an antenna within a radius of 400 km, radio amateurs from the Donetsk, Zaporozhye regions, Turkey and Bulgaria were repeatedly convinced of this.
But “the best is the enemy of the good,” the author was repeatedly convinced. Well, that year there were no duralumin rods at the dacha for Moxon’s 4-element modernized small-sized rectangle, so I had to make a “Super J”. To do this, to the J-antenna configured as mentioned above, it is necessary to connect to the top of the emitter another half-wave sheet of size B" = BA. This sheet is connected through a short-circuited quarter-wave cable 42 cm long (for 145.3 MHz), made similarly to the described cable for J-antennas.
But the spacer insulators must be made narrower so that after manufacturing the cable can be rolled around the insulator (Fig. 4) into a ring, wrapping it with electrical tape. The upper end of the already configured J-antenna is connected to one end of the loop, and a new emitter is connected to the second. This entire structure also rises vertically. The length B" of the additional emitter is adjusted to resonance at 145.3 MHz. Everything... +2.5 dBd to your J-antenna is guaranteed.
Alexander Karakaptan (UY50N), Kharkov
One of the radio amateurs in the neighborhood (our region) called and asked why he couldn’t hear Oscar -7, although according to calculations it was flying directly over Goncharovsky. Since this is not the first time this question has arisen, I think it will be necessary to repeat it. I gave a good review for GUHOR reasons on Hammaniya. I think that there is no need to duplicate this material, and therefore I will answer on this specific situation. There are several logical “I”s here that led to the fact that he probably won’t hear the satellite in the future.
Gosha is an alien ;-)
When reading an author, it is sometimes difficult to imagine him. For example, in my youth I read a lot of Alexander Greene, who actually wrote a lot of things besides “Scarlet Sails”. But when I saw his portrait I couldn’t believe my eyes. The only exception is Mayakovsky, as he writes and looks the same. So that no one doubts what Gosha the radio operator looks like, Sasha Litvinenko UR5RP sent a photo. "Gosha the radio operator writes to the site." And whoever did not believe my good forecast of the HF bands for these three days is to blame: only in the last half hour in the telegraph Jamaica, Lesotho, Senegal and the Dominican Republic. In RTTY Something I didn't have before.
OQRS: QSL from the Internet
I have already written before about how to get a card via the Internet. The method caught on and now almost all DXpeditions run this service because it makes the exchange easier and cheaper for both parties. For those who find it difficult to understand English terms and abbreviations, I will “decipher” the description of how to do this. Well, first you need to have before your eyes all the data for connections with this expedition. In my case it will be 7O6T. To do this, we go the standard way, starting with QRZ.COM, then follow the links until we see a picture of online check of your QSOs. Below there is a REQUEST QSL button. We click on it. 
Now the work is more difficult: In the left column there is initial information about connections,
SDR and LAN
It is clear that life without wires is better. I'm talking about Wi-Fi and so on. wireless technologies. Here's another plus. My first VHF SDR was sealed in a metal box, with a good shielded antenna input (who remembers the photo from earlier). And now I have a tuner in its original case (photo two posts below), rubberized, with a convenient latch connector instead of a thread or bayonet mount. It works well, but I decided to watch a 3D movie on my new box. The film, of course, is on the laptop, and the TV reads it via Wi-Fi. But it slows down from time to time. I decided that it was slowing down due to Wi-Fi radio interference; the braking was painfully sporadic, rarely, that is. I turned on a regular LAN router, plugged in the Ethernet cable and was horrified: my SDR receiver had shut up.
SDR panorama in VHF transceivers
Sergey UA0ADX
Working via satellites, in particular SSB and CW, I encountered a problem: the orbit is short, the range is quite wide. Sometimes there are a lot of correspondents, but you won’t always find them when you search. Either they switch to reception and you run past, or you work on a general call and don’t hear anyone who works lower or higher. The satellite flies by quickly, sometimes without results. This circumstance made me think about the SDR panorama. The first step was to purchase an SDR receiver. The choice fell on the most budget-friendly of the advanced ones)) - SDRplay RSP-1, there are several other good RTL SDRs, which I unfortunately learned about after purchasing the RSP-1. Next, I had to figure out how to “hook it up” to the same antenna or antennas on which I am working, respectively, in order to see the real picture, while avoiding any switching, detours, etc., due to the unreliability of which more than one device could burn out)) .
SV2AGW Packet Engine
Live and learn! :-) I just learned that a widely used packet network and node emulator on an audio card can convert signals from dual-band transceivers to a single logic converter. I mean KISS AGW by DK3WN. A little introductory information for those who don’t like satellites as much as I do. Our Windows displays what the satellites transmit in telemetry lines on the screen in the form of acceptable screen symbols of one or another layout (Greek, Cyrillic or Latin). In order to correctly recognize this information and use it to display real telemetry data, the resulting strings must first be converted to ASCII strings (files), and only then decoder programs “chew” it. So, DK3WN uses SV2AGW sound modem as a modem for its converter (as one of the KISS AGW variants). In its settings you can use both of the stereo channels of your audio card.
Lighthouse on Arduino part 2
Modules are usually connected via five wires: VCC - power, GND - ground, CLK - clock pulses, STR - strobe and DATA (IO). All modules have pin designations on the module side, and the pin on the Arduino side is assigned in the program. For example, a temperature sensor does not require clocking and its output is connected to analog input A1. A clock, for example, has data to transmit, so the connection is five-wire. The assigned pins can be found in the body of the program. The same goes for the button and display board. With simple signals such as PTT, CW keying, connecting an additional antenna or turning on an additional fan, only one pin is enough. They are also assigned in the program and connected through optocouplers to actuators: transceiver, switch, fan, etc. In the diagram it is all transparent. Pin 10 of the Arduino is used to provide permission to the beeper and connects directly to the BUZZER. Since modern transceivers all have self-monitoring in the telegraph, it is not included in this model. But, if you want to turn on, for example, this beacon in FM mode, you will need this signal.
VHF antennas with J-matching
The J-antenna (Fig. 1) has long been and deservedly popular among radio amateurs. Its design is simple, it is easy to set up and matches the feeder of any resistance. However, its large size (total length is 0.75λ) makes it difficult to use on HF bands. But in the VHF bands it is widely used. As can be seen from Fig. 1, it is a vibrator with length λ/2, powered from the end through a matching device made in the form of a quarter-wave open line, closed at the lower end.
The high input impedance of a half-wave vibrator when fed from the end (several kOhms) is easily transformed to the cable resistance by choosing the distance from the power point to the closed end of the line. Using an open line as a transformer ensures low losses at high transformation ratios. J-antenna gain - +0.25 dBd, i.e. slightly exceeds the dipole gain due to the radiation of a two-wire line. The vertical J-antenna, due to incomplete symmetry, has little radiation with horizontal polarization (Fig. 1a).
We modify the J-antenna by bending the quarter-wave line by 90 degrees (Fig. 2).
By slightly adjusting the dimensions, it is not difficult to achieve good matching and 0 dBd gain. However, with this version of the antenna, a noticeable part of the radiation is already horizontally polarized (Fig. 2a). It is caused by a common-mode current in a two-wire line, which plays the role of a counterweight (pantograph) in the J-antenna.
Let's add another half-wave vibrator, connecting it to the free end of the two-wire line (Fig. 3).
The design is now completely symmetrical in the vertical plane, there is no common-mode current in the two-wire line, as well as radiation with horizontal polarization (Fig. 3a).
This option is a collinear antenna of two half-wave vibrators fed through a quarter-wave line closed at the end. This antenna is described by SM0VPO (1) on his website in the article "6 dB collinear VHF antenna by Harry Lythall - SM0VPO". Its gain (about 2.4 dBd) is obtained by narrowing the radiation pattern in the vertical plane. In the horizontal plane, the radiation diagram is circular. The antenna is structurally very simple and can be made from one piece of rod or tube. To maintain its symmetry, it is advisable to connect the power cable through a balun transformer. SM0VPO uses a balun transformer in the form of a U-elbow; you can limit yourself to several ferrite rings placed on the cable near the antenna feed point. For brevity, let's call it a Super-J antenna.
What further modification of this antenna is possible? By adding reflectors to it, we get a 2-element Super-J antenna (Fig. 4). This is already a directional collinear antenna. Its gain is +5.8 dBd.
By adding directors, we get a 3-element Super-J antenna (Fig. 5). Gain - +8 dBd.
An attempt to add a second director noticeably increases the length of the antenna, but gives an increase in gain of only 0.8 dB. What is the advantage of these antennas over multi-element Yagi? With the same area, their gains are approximately equal, but the advantages of Super-J antennas are the short boom length and the associated small turning radius, and ease of matching. The disadvantages include the need to use a dielectric mast, at least its upper part. Figure 6 shows photographs of a 3-element Super-J antenna for the 2-meter range, made of aluminum rod with a diameter of 8 mm.
Fig.6. General view of the 3-element SuperJ antenna.
A dielectric mast (for example, fiberglass) and an insulating spacer can be placed in the spaces between the elements (they are shown in bolder lines in Fig. 7).
It is better to route the power cable horizontally behind the reflectors and return it to the mast in a wide loop, away from the ends of the reflector. In the area near the antenna, it is advisable to place ferrite cores on the cable every 0.5 m.
Fig.8 View of a 3-element Super-J antenna on a mast
The design dimensions of the 3-element Super-J for frequencies of 145 MHz and 435 MHz are shown in Fig. 9 and in table 1.
Dimensions are given in centimeters and between the axes of the conductors. Input impedance at the power point is 50 or 200 ohms. If a U-elbow is used for balancing, it transforms the feeder resistance to 200 ohms, so the connection point to the two-wire line will be slightly further from the closed end. In this case, the dimensions of the matching loop change slightly (see Table 1).
Table 1.
|
Frequency |
Rin, |
||||||||||
|
52,5 |
34,5 |
||||||||||
|
52,5 |
34,5 |
41,5 |
|||||||||
|
14,7 |
17,5 |
17,7 |
16,3 |
11,5 |
0,25 |
||||||
|
14,7 |
17,5 |
17,3 |
16,3 |
11,5 |
13,8 |
0,25 |
* -- the size is specified during setup.
D is the diameter of the aluminum or copper conductors from which the antenna is made.
For ease of setup, it is recommended that the matching device be made with two “sliders” (moving contacts): one that closes the two-wire line is used for tuning to resonance, the second that connects the feeder is used for matching to the minimum SWR level. This allows you to quickly configure the antenna, but after selecting the positions of the “sliders”, you must ensure reliable contact (by soldering or bolts). The efficiency of the antenna greatly depends on the contact resistance. It is worth remembering that copper-aluminum contact is inadmissible and that the contact is protected from moisture. The requirements for contact resistance at the open end of the J-leg, on the contrary, are not strict, since the current there is minimal. An antenna for an average frequency of 145 MHz was made from an aluminum rod with a diameter of 8 mm. It was attached to a fiberglass tube with a diameter of 23 mm, used as a mast. A ferrite tube placed on a cable near the antenna feed point was used as a balun. First, a single element Super-J antenna was tested (Fig. 3). It was noticed that when the antenna is placed on a wooden table parallel to the ground and when it is positioned vertically, the settings do not match. Therefore, the antenna must be tuned by installing it vertically. It is enough that the distance from the lower ends of the vibrators to the ground is about 0.5 m. By moving the shorting jumper along the two-wire loop and moving the cable connection points (these adjustments are interdependent), it is quite easy to match the antenna to SWR<1,1 на желаемой частоте. полоса частот по уровню ксв<1,5 превышает 5 мгц. затем к мачте и активным вибраторам были прикреплены бумы, также выполненные из алюминиевого прутка диаметром 8 мм, поскольку не имелось под рукой диэлектрических трубок необходимой жесткости. в средней точке вибраторов напряжение близко к нулю, поэтому проводящий бум слабо влияет на характеристики антенны, что подтвердило предварительное моделирование. на бумах были установлены рефлекторы и директоры, длины которых выполнялись по расчету модели с помощью программы mmana. пассивные элементы резко снизили входное сопротивление антенны. однако слабо выраженный минимум ксв был найден. передвигая перемычку, и сдвигая точки подключения кабеля, нашли положение, когда минимум ксв соответствовал частоте 145 мгц и уровень ксв не превышал 1,2. длины вибраторов не регулировались. по сравнению с настройкой одноэлементной антенны настройка трехэлементной антенны значительно более острая и критичная. полоса по уровню ксв<1,5 составляла около 3 мгц. длина шлейфа оказалась несколько меньше, а расстояние от замкнутого конца шлейфа до точки питания кабелем с сопротивлением 50 ом несколько больше расчетных значений. работа антенны предварительно оценивалась в городских условиях (кругом были высокие здания, полностью закрывавшие горизонт) при расположении ее оси над землей на высоте всего 1,5 м. по сравнению с четвертьволновым автомобильным штырем она давала прирост сигнала на 2-3 балла при связях на расстояниях 10-50 км. направленность в горизонтальной плоскости была ярко выражена. общее впечатление - антенна работает. более аккуратные оценки работы антенны были сделаны на открытой местности в дачных условиях при подъеме антенны на мачту высотой 7 м. сравнивались антенна рис.6 и четырехэлементная антенна "квадрат" с вертикальной поляризацией (рис.10). антенны устанавливались на одной и той же стеклопластиковой мачте в одном и том же месте. использовался один и тот же кабель в качестве фидера и один и тот же трансивер. оценивалась работа по открытию и слышимости репитеров, расположенных на расстояниях от 30 до 100 км и оценкам корреспондентов при проведении qso в прямом канале на расстояниях до 70 км.
Fig. 10. The “4 square” antenna with which the antenna in Fig. 6 was compared.
In most cases the estimates were very close. If you've heard "square", you've also heard SuperJ. The four-element "square" had a narrower radiation pattern in the horizontal plane, so it had to be aimed more accurately at the correspondent to get maximum rating; the Super-J was almost not turned. The general impression is that the antennas have approximately equal gains and good back-lobe suppression. The antenna under test is two times lighter than the “squares” and has a significantly lower torque and windage. Figure 11-14 shows the antenna design elements.
Fig. 11. Short-circuit jumper, cable connection unit and balun ferrite choke.
Fig. 12. Mounting unit for a two-wire line to a mast.
Fig. 13. Mounting unit for booms to the mast.
Fig. 14. Unit for fastening elements to booms.
Attached are files for modeling the described antennas: MMANA files
RU3ARJ Vladislav Shcherbakov, [email protected]
Photos by RW3ACQ Sergey Filippov, [email protected]
_________
(1) SM0VPO in his article for some reason gives the antenna gain relative to some quarter-wave whip (apparently a car antenna), where its 6 dB comes from.
As they say, at the request of the workers, we are returning to VHF issues. The fact is that recently there has been a significant increase in prosharok (this is translated from Ukrainian into Russian as a layer, layer) of people who respect the word “shara” :-) There is no need to strain with huge antennas, buy expensive transceivers, or participate in two-day competitions. I bought myself a tiny radio for 50 bucks, or even cheaper, some SDR at 145, asked the locals at what frequency the repeater operates and here he is, a newly minted radio amateur :-) I’m joking, of course, but in every joke...
Therefore, in order for such radio amateurs to have every right to be called real radio amateurs, in addition to the flexible “rubber band” of a 145 MHz radio station, many get an external antenna for their vokitoki. As a rule, this is a very popular J-antenna due to its simplicity and ease of setup. For these reasons, it is often called a "baby" antenna. There are a dime a dozen such designs on the Internet; even this site has a calculator for accurately calculating the size of elements for a specific frequency.
It must be said that the vast majority of “purchased” antenna models are collinear antennas, that is, “adult” antennas that have some kind of gain due to the addition of signals in the main and added parts. It's like two in one. Well, to be completely honest, it’s one and a half in one. For those who already have a J antenna and are working, we can offer an upgrade that will convert the “children’s” J antenna into an “adult” collinear antenna design. Well, for those who don’t yet have any antenna, this is a design that has a circular radiation pattern, but its gain is greater than one. At least 3 dB (5dBi). The horizontal “appendix” that you see in the figure is an element of signal addition, pairing the upper and lower parts of the antennas. Anyone who has opened Rothhammel’s book at least once will immediately recognize it as a quarter-wave transformer :-)
So, we have an extremely simple system for connecting the reduction cable and, by the way, what is even more important, the possibility of excellent antenna matching, with an important add-on in the form of a quite decent antenna gain.
Another advantage of the design is its absolute simplicity: everything can be assembled on a cross (or L (or more precisely T)-shaped connection) from two blocks of wood 40-50 mm wide. Moreover, the horizontal part can be only 10 centimeters long: the transformer sticking out to the side at a distance of 10 centimeters from the vertical part of the antenna can be smoothly bent in the horizontal plane (that is, maintaining perpendicularity to the vertical). In the picture, the antenna is made of labor with a diameter of 11 mm (pieces of an old antenna array from an army RRS), but if there are problems with the tubes, an aluminum rod from old power cables with a diameter of even 5 mm can be used as a material. Of course, this will affect the broadband of the antenna and the lengths will have to be adjusted when tuning to large values, but it still needs to be adjusted, and our structure is still made of wood :-)
In short, I think I will spend more time describing the setup of this antenna than on the design: it is not new and is absolutely transparent. Two comments still need to be made regarding the design. First: the quarter-wave transformer at the far closed end should be made with a movable jumper. That is, make the length 15-20 mm longer and close the elements with a movable jumper with a bolted clamp. Second: at the very top of the antenna, make a semi-telescopic end in the form of a section of the main pipe, an inner tube of smaller diameter and a clamping clamp. If these are not tubes, just add a couple of centimeters to the calculated length for subsequent shortening. :-)
indpol Let's move on to the description of the devices and the setup method. Of the instruments, it is best to have something like (in order of desirability:-): an antenna analyzer, an external SWR meter of the corresponding range, a field strength meter and, as the last, worst in terms of accuracy of the device, a test beacon for the 145 MHz range. I think a pair of field strength meter - external SWR meter will be enough. First, let's make a meter (for those who don't have one yet :-). Here is the circuit that I have been using for about 30 years. The only important thing is the cutoff frequency of the diodes used. It is better to use germanium diodes and possibly higher frequency ones. Two arms of a dipole up to a meter long are attached with insulating tape to a meter-long stick, the rectifier bridge is also assembled there, and the measuring device on a long two-wire line (at least 10-15 meters) is carried directly to the base of the antenna, where adjustment work will be carried out. As you guessed correctly, your radio will be used as a signal source at the desired frequency. 
It is best to connect the SWR meter between the antenna itself and the feeder you are going to use. The first setting is to determine the height of the cable connection point at the J node of your antenna. It is clear that at the desired frequency and it is clear that at the minimum SWR. Having achieved a minimum (not necessarily one), you can move on to the second operation. Having turned on the transmitter and seeing the deviation of the needle on our field strength meter, we relate it to the distance at which the deviation of the device is still noticeable. After this, by changing the position of the jumper on the quarter-wave transformer, we achieve maximum needle deflection. Then, by changing the length of the last, highest element, also to the maximum, we tune the antenna to resonance. After the antenna is raised to its working height, the frequency will go up somewhat, so on the ground it must be tuned 150-200 kilohertz lower. Having double-checked our settings, we can move on to the final stage: finally determine the feeder connection point based on the minimum SWR reading of the meter. The SWR should be close to unity. After that, reconnect the cable from the radio directly to the antenna and, voila, raise it to the operating frequency. If you didn’t tear, break or bend anything while lifting, the result should be the same.
Also with a pie chart and gain Double Kharchenko
- Back
- Forward
On the twenty you can clearly hear the rare IOTA AF109 - Nelson isl. SU8N card via SM5AQD. Geographically 20 km from Alexandria. The island is 150x350 meters, almost all sand :-) but they hear well. They work by numbers and accepted me without any problems in the first rows at my hundred watts. True, I think their antennas are also directional. They say they will be there for a week. And this is my first Egyptian island :-)
Parsing QSL
So God willing, in installments. The smell of the fire from the summer expeditions of past years has long disappeared, but I still check the log and send cards to EN5R and EN25R. I’ve accumulated a lot of connections, but that’s not what I’m talking about. Sitting doing boring work, we are sometimes pleasantly pleased by the desire of correspondents to cheer us up. As an example - Vladimir Doroshenko's card UX7MM. Thank you, Volodya, I feel better. :-) 
P.S. So we are also like-minded people :-) I'm talking about qrz.com
Simple rotary on Arduino
Only the very lazy have not written about a rotating device for an antenna controlled by Arduino. And yet, it seems to me, I “drew” the simplest thing :-) Given the apparent complexity of rotary devices, or rather control panels, with a certain amount of savings you can create a very simple device that allows you to greatly save body movements :-) I have some experience in operating devices type Yaesu G800DXA and G5500. Of course I’m glad that I have them at all, but they also have their drawbacks. The first is the crooked preset system in the G800: very inaccurate, although it is difficult to “aim”. The G5500 has no presets at all. Despite the fact that the mechanisms themselves support a fairly accurate rotation indication, holding the buttons pressed until the antenna slowly reaches the desired azimuth is tiring.
Ukrainian, good mood! Fox hunting :-)
Thanks to my friend Alexey (UT0RM) for finding and sharing. Help for non-Ukrainians. “Vopli Vidoplyasova” is a cult Ukrainian band that combines nostalgic hard rock, hard wave, retro elements and the flavor of local folklore in its music. The result was beyond praise: hardcore punk, enhanced by the sound of a button accordion, Ukrainian jokes and masterfully presented on stage. "Fox Hunt"