## Monday, December 30, 2013

### Calculating vibrator logoperiodic antenna

Broadband log-periodic antenna aimed work without rebuilding ten - twenty fold and the broader range of wavelengths . Log-periodic antenna can be used as antennas connected to the HF and VHF bands , as well as for receiving TV channels . The figure shows the log-periodic antenna, it consists of a series of vibrators connected with consistent variable phase to two-wire line . Dimensions vibrators and the distance between them decreases exponentially towards the connection point of the feeder or coaxial cable. Behind the longest dipole antenna located logoperiodic jumper that improves coordination with feeder . The distance between the jumper and the vibrator is chosen experimentally in the antenna settings. Feeder (coaxial cable with an impedance of 50-75 ohms) goes inside one of the tubes of a double line (no matter through what) . Parameters and log-periodic antennas determine the size structure of the period "t", equal to the ratio of the length to the length of follow- vibrator and the previous angle "a" at the apex of the triangle , which are inscribed vibrators . The closer the structure period "t" by one and the smaller the angle "a", the higher the gain the log-periodic antenna. But this increases the size of the antenna , often choose "t" = 0.8-0.9 and the angle "a" = 30-45 degrees. At each frequency waves in the operating range of the work involved those vibrators, resonant frequencies that are closer to this frequency (3-4 vibrator ) . Strengthening logoperiodic antenna are obtained with approximately 5-7 dB. In order to calculate the size of the log-periodic antenna vibrators need to know the length of the extreme waves Lmax and Lmin operating range. To determine the length of the longest start vibrator l1 it should be 0.55Lmax, built on an isosceles triangle with an angle "a" at the top equal to 30-45 degrees, the base of the triangle will vibrator l1. Second vibrator logoperiodic antenna located at a distance d1 = (0.15-0.18) Lmax from the first. The dimensions of the vibrator are uniquely determined size of the triangle. Likewise, the following dimensions are determined antenna dipoles . Distance d2 = d1 * t, d3 = d1 * t and so on. This arrangement continues until the next length is not equal to oscillator 0.45Lmin, this vibrator will last

## Sunday, December 29, 2013

### H antenna

It is known that a single dipole antenna tuned neslishkom has a high gain. But if you use two of these antennas connected a phased power line, then we can increase the gain of the antenna. The result is an antenna system comprising two types of dipole antennas, is reminiscent of the Latin letter h and with the name of "lying h". This antenna (lying h) feeding points has high input impedance and it soglosovat to the power supply line of arbitrary length requires use quarter wave transformer. Antenna type "bream h" has exactly takuyuzhe radiation pattern in the horizontal plane as the normal dipole antenna. But the radiation pattern in the vertical plane in the investigation narrows the location of two dipoles of each other and that this expense and get a win to be reinforced. But this antenna system has its drawbacks - namely, suspension height. Necessary to lower the dipole antenna "lying h" was at the height of not less than L / 2 + height of the top of the dipole. The approximate gain of the antenna "lying h" 5-6 dB! And it is much more than a single dipole. The figure shows the dimensions of the antenna "lying h" for three ranges of 14, 21, 28 MHz. As the supply line used by the resonant power line, it Is located horizontally to a measure on the longer L / 2. For this it is necessary to use another mast. Radiation pattern is the range of frequencies used.

### Vertical delta-loop antenna

This month I would like to share an idea from my sketchpad with you. I am planning to build a vertical delta-loop antenna for 20 meters. The reasons for choosing this design:
• My favourite HF band is 20m
• Delta-loops for 20m are manageable in size
• Loops are quiet on receive
• Vertically polarized loops are well suited for DX
I found the delta-loop overview below at the website of W5SDC:

Delta-loop overview.
﻿
My choise of shape will be version D because if offers a low radiation angle, which is necessary for DX. The sketch below shows how I plan to build the antenna:

Delta-loop antenna for 20m.
﻿
A delta-loop antenna with ATU was described by WB8IMY and published in QST May 2002: One Stealthy Delta. This article is worth studying if you consider constructing a loop antenna.

OZ1BXM Lars Petersen

### Building a 2m quarter-wave ground-plane antenna

The first antenna that you should consider building is the quarter-wave ground-plane antenna for the 2m band. They are very easy to build and will perform better than the antennas that come with most handhelds.

The quarter-wavelength, ground plane antenna is made up of one vertical element, called the driven element, and four radials. The radials make up the ground plane. An easy way to make this antenna is to use an SO-239 coax connector. The driven element is soldered directly to the center conductor, while the four radials are connected to the four holes in the connector’s flange. See the figure at right.
A simple 2m antenna can be made with an SO-239 connector and four short pieces of stiff wire.

Now, let’s calculate how long the elements should be. Since the wavelength of a radio wave is equal to 300/f (MHz), one quarter wavelength will be equal to 75/f (MHz). At 146 MHz, therefore, the length of the driven element is:
75/146 = .51 m

In practice, we have to make one more adjustment. Because a radio wave travels more slowly in a wire than it does in free space, the wavelength will actually be about 5% less in a wire than in free space. So, we multiply the wavelength in free space by .95 to get the length of the driven element:

.51m x .95 = .49m = 19.25 inches

The radials should be about 5% longer than the driven element. This isn’t really very critical, so if you make them 20.25 inches long, the antenna will work just fine.

You should make the elements out of a stiff wire. 12 AWG copper wire will work for experimentation purposes. Welding rod might be better for a more permanent antenna.
You need to solder the 19.25-in. driven element to the solder cup of the center conductor of the SO-239 connector. Attach the radials to the holes in the flange of the SO-239 connector with nuts and bolts. You can also use these nuts and bolts to mount the antenna to some kind of bracket. Bend the radials out to a 45-degree angle, connect a coax cable to it, and start having fun

### 10m loop antenna.

Here’s something interesting about the loop antenna and folded dipole antenna. If you read my blog, you’ll remember that I recently put up a 10m loop antenna.
Well, this loop has a full wavelength of wire and is twice as high as it is wide. In this configuration, the antenna has a feedpoint impedance of 50 ohms.

If you take that same wavelength of wire and configure it so that the height is very small with respect to the width, you have a half-wavelength, folded dipole. In this configuration, the feedpoint impedance is about 300 ohms.

Back in the day, hams used this to make folded dipoles out of 300-ohm twinlead, the same kind of wire used to connect TVs to external antennas. Not only did the twinlead serve as the antenna wire, but it also served as the feedline, and because this twinlead was mass-produced, it was relatively inexpensive. To match the 300-ohm impedance to a transmitter, you did need some kind of transmatch or a balun, but overall, this type of antenna works very well and was cheap to build.

One of my favorite things to do is talk with other ham radio operators through satellites or the International Space Station (ISS). To do this, I stand on a rooftop and tune a handheld multiband radio while tracing the orbit of a satellite or the ISS with my homemade yagi antenna.
Orbiting satellites such as AO-51, SO-50, and AO-27 act as repeaters, relaying signals from low-power transceivers like mine back to hams elsewhere on the planet. So if you know where to aim the antenna, you can communicate around the world via space. The ISS also has a repeater, and occasionally, when we’re lucky, the astronauts themselves exchange transmissions to communicate with hams on the ground.

To listen to these signals from space, you don’t have to be a licensed ham radio operator, or even stand on the roof. You can do it in your own backyard with an off-the-shelf UHF FM radio. The whip antenna on the radio might let you hear satellites and the ISS, but you’ll get far better reception by making your own yagi antenna, which takes about an hour and costs less than \$25 (not including the cost of your radio) using materials from your local hardware store.

## Friday, December 20, 2013

### VHF wire antenna for field use

As a VHF antenna for field use, you can use the wire antenna for the range of 144-146 MHz. This antenna wire has a sufficiently large size of its length 16 meters 8L is the wavelength. A feature of this wire antenna designed as a radio amateur from Germany is that it is made on insulating cord. All elements of VHF antenna made ​​of wire with a diameter of 3 mm. Part of Directors of the wire are the same size equal to 915 mm (antenna DJ4OB in the figure below). The vibrator is made of a wire or tubing of different diameters, the material from which the tubes are made to be the same. The upper antenna element DJ4OB vibrator has a diameter of 8 mm and a bottom diameter of 2 mm. Input impedance of wire antennas for VHF band 144-146 MHz is about 240 ohms. The antenna gain of about 15 dB. Since the antenna is a rigid base (yoke), it can easily be rolled up and thereby transported to the place of deployment. This wire antenna can operate only in one direction for obvious reasons.

## Friday, December 6, 2013

### wire antenna w3dzz

Amateur radio is very popular among the wire antenna w3dzz, description and operation of this wire antenna often occurs in amateur literature . This popular wire antenna w3dzz is that with small linear dimensions , it can work in several amateur bands . The figure shows a further embodiment of the antenna w3dzz. This version of the wire antenna is designed to work in the amateur bands 1.9 , 3.6, 7, 28 MHz . Total length of the antenna about 67 meters. To connect to the transmitter output w3dzz can use a coaxial cable with a characteristic impedance of 50 or 75 ohms. Coils are wound on a frame 25mm in diameter of a copper conductor with a dielectric diameter of 1 mm, number of revolutions 38. Capacity (c1 and c2) capacitors antenna is 470 pF (four series-connected capacitor with a total capacity of 470 pF ) , the voltage at which shall be calculated these capacitors should be at least 500 volts. These capacitors are located inside the mandrels and are filled with sealant. Frequency tuning L1C1 and L2C2 is 3580 kHz . VSWR w3dzz at frequencies from 1840 to 3580 not more than 1.5, 7.1 and 7 ... 28.2 ... 28.7 - 2.

## Friday, November 15, 2013

### The magnetic loop antenna wire portable CB radio

The figure below shows the magnetic loop antenna for cb band , made of copper wire with a diameter of 2 mm. The antenna has an impedance - 50 ... 75 ohms and a low reactivity. The bandwidth of the magnetic loop antenna - 600 kHz. Air condenser is mounted on a prison setting . The antenna is insensitive to the effects of human and balances. This antenna radiates in the main magnetic component of the electromagnetic wave , it can not compare in terms of field strength with a whip antenna , because the whip antenna emits electrical component of the electromagnetic wave , and measurements for the probe should be carried out on the electrical component and the frame - by the magnetic component . Were compared between the standard helical antenna cb radio and wire magnetic loop antenna was tested in the communication range . It was found that under equal distance communication using magnetic antenna was not less than 1.5 times the open area, and 2 ... 3 times larger in urban environments . In this case, a significant effect of the magnetic orientation of the antenna.

## Monday, November 4, 2013

### GP antenna for four bands 28, 21, 14, 7 MHz

The figure shows the antenna GP for four bands : 28 MHz , 14 MHz , 21 MHz and 7 MHz . The main antenna - mast has a height of 9.95 meters, it is usual GP antenna for a range of 7 and 21 MHz for the other two antennas GP she is still supporting mast. This antenna - mast is earthed at the connection point and the ground is connected to the counterweight to the 10.5 m long ( 7MHz ) , 5.20 m ( 14MHz ) , 3.5 m ( 21mgts ) , 2.45 m ( 28 MHz ) . and inclined at an angle of 135 degrees, so it turns out that the input impedance of the three bands GP antenna is 50 ohm, allowing you to connect without any problems to connect the coaxial cable of the same resistance. This is most effectively four band antenna operates GP is in the range of 21 MHz , as in this range for the longest antenna - 3/4L mast contains a wavelength range of the counterweights to improve alignment with the cable. In the range of 7 MHz antenna GP consistent color across a transformer in the rest of the condensers . The disadvantage of this antenna GP - is that its base should be at a height of about 7 meters (to allow the angle of 135 degrees). Advantages that the antenna can be grounded.

## Sunday, October 20, 2013

### Wire antenna type cubic American ham

In the American Journal of QST for 1973 hobbyist WA1MKR Max Blumer was proposed antenna, which is a wire loop with a perimeter equal to the wavelength. The figure shows that the wire loop and the principle of its formation. Was based on a common loop antenna ( left panel ) , power points X and Y. This wire frame radiates vertically polarized wave in two directions perpendicular to the plane of the frame antenna A-A '. The figure shows that the center of the antenna is converted into a rectangular wire antenna , wherein the antenna radiation characteristics are not changed. In the following figure the rectangle becomes a cube . With this transformation of the perimeter wire antenna remains unchanged, but the most important thing that the length of the sides of the new antenna is transformed into a cube is reduced to a length of L/10. But unlike conventional wire- frame in this changing pattern of the antenna in the vertical plane of the antenna also radiates vertically polarized wave , but the direction of the radiation is not bi-directional and omni-directional . Author WA1MKR this antenna realized this dish with origins in the 144 MHz antenna is connected to the coaxial cable with an impedance of 50 ohms. SWR was 1.2 ... 1.4 . In the study of pattern was found that all the same it is not really a pie chart , probably because of the shielding properties of the cable and the structure. In the future, the author WA1MKR was made the same wire antenna but for the range of 21 MHz in this band , it was almost the same features except for the SWR, it is not much higher. The antenna has shown good results.

## Saturday, October 12, 2013

### Upgraded wire antenna type inverter ranges 7 and 3.5 MHz

Not always, amateur radio is the ability to set effective long wire antenna for the 3.5 and 7 MHz . If you want to install a wire antenna type inverted V and there is no place you can upgrade this antenna a bit , reduce the size of the antenna input of the extension coil . As can be seen from the figure below size wire antenna extending spools approximately equal to the size of half-wave dipole for 7 MHz . The mast antenna has a small height, which is approximately 7 meters, the lower ends of the antenna is at a height of approximately 1.5 meters from the ground . Also from the figure that the power antenna wire modernized type inverted V through the delta transformer via a coaxial cable with an impedance of 50 ohms ... 75 . For a more exact matching transceiver must have the tuner . Since this wire antenna significantly affects the properties of the soil ( container terminal ) , then after the installation requires careful tuning . When you set up a wire antenna to watch its resonance and SWR. Changing the resonance of 100 kHz to 3.5 MHz band can occur when the length of the segment b by 5 centimeters. If you still do not get the minimum SWR you can try to change the point of connection of the delta - the transformer. With this upgrade wire antenna type inverted V, the antenna in the range of 3.5 MHz to baseband . This antenna is useful in field conditions and in areas with limited space.

## Sunday, October 6, 2013

### cruciform dipole antenna

It is known that the directivity pattern of a conventional dipole antenna has the shape of a horizontal eight . It is obvious that in order to be able to carry out qso with correspondents located in different areas of need for this dipole is placed on the rotator . But if you do not have a rotary device that can apply an antenna system of two perpendicular arrangement of the two dipoles. This dipole antenna system is connected via a single coaxial cable dipole excited with a phase shift of 90 degrees to form a cross-shaped antenna ( first figure) . Diagram of a cruciform dipole system in the horizontal plane has a substantially circular shape . From this figure it can be seen that both dipoles are connected through the quarter wave transformer . Strengthening of the cross- dipole system is not great and there are some difficulties in the negotiation. Increase efficiency of the antenna system and hence its gain and to avoid difficulties in coordination can be applied if the antenna system is based on loop dipoles such loop dipole itself has a higher gain and efficiency than conventional bit wideband linear dipole. In the second picture a) - wiring diagram of the dipoles and Figure b) - the radiation pattern . As can be seen from the figure the coaxial cable is connected directly without the agreement and the point where the cable impedance of 75 ohms . Input impedance of each dipole is 300 ohms. Dipole disposed at a distance equal to L / 2 (half wave ) . Currents flowing in the opposing antennas are shifted from each other by 180 degrees, and thereby forming a circular pattern . Placing a few of these antennas on top of each other giving you greater gain relative to a conventional dipole.

## Saturday, September 28, 2013

### Matching the supply line to the antenna output of transmitter

The figures below show matching circuit transmitter output stage and power supply line connected to the antenna. Some of these schemes are seldom used because they have a weak filtering harmonics . Figure a) shows a matching circuit in which the antenna is connected directly to the output circuit of the transmitter. Matching is done by changing the capacitor C1, or change the point of connection to the antenna circuit ( change in the number of turns ) . As an indicator that will show the output matching circuit and antenna can be applied ammeter or a neon bulb. But the maximum ammeter or glow lamps can not always talk about the good coordination of the system. The current can reach its peak in the event of a standing wave in the supply line and the devices may not be current at the antinodes . This situation can occur when a wire is broken antenna SWR and has an infinite value . The following diagrams b) and c) are diagrams in which approval is best filtering harmonics of the transmitter. But because of the presence of inductive coupling between the coils L1 and L2 in the antenna section of the inductive reactance , an additional character. Sometimes when a large inductive coupling between the coils L1 and L2 can occur a substantial redistribution of the currents in the power supply line and the antenna. In order to compensate for the inductive coupling between the coils can be applied capacitance C3 - Figure d). But in this case, the circuit is interrupted by the DC that prevents run-off from the antenna electrostatic discharges. In the figure e) shows the matching circuit and the power line transmitter output stage transistor . Then use the usual resonance system , increasing resistance and the degree of transformation is the selection of the capacitors C1 and C2. In the VHF band can apply an agreement in Figure f). In order to reduce the level of higher harmonics can apply a Faraday shield (all circuits except a)). As this screen, you can use the shell coaxial cable - figure h). This screen can be used when a particularly high level of harmonics . Loop cable is closer to the edge of the grounded coil output stage . Even more harmonic filtering can be applied if the agreement scheme on the image i). In this circuit, an antenna circuit is divided by filtering and matching circuit . As the coil connection can be used here as a coaxial cable as shown in the previous figures . Circuit performing the role of filtering and matching can be taken away from the transmitter output stage and place them in a more convenient location and the connection between these stages can be performed from any piece of cable with a characteristic impedance . Loss in this case is extremely small and can be neglected . The circuit in Figure i) is called a filter Collins.

## Thursday, September 26, 2013

### Amateur G5RV wire antenna

Amateur G5RV wire antenna in the picture with a size of 31 meters, it is the transition between the antenna option with long arms and a 54-meter antenna with an arm length of 27 meters. By wire antenna connected two-wire power supply with an impedance of 300 ohms (balun). Length of the power line should be 12.90 meters. This line acts as a power transformer. Towards the bottom of the feed point of the transformer is connected coaxial cable (Figure).

In the range of 28 MHz each half G5RV wire antenna has a length 3L / 2. Diagram of a shape of the antenna length 3L. In-phase excitation power gain compared to a conventional dipole is 1.8. In this range, the antenna G5RV works well. Since the length of the line is transforming 5L / 4, the wire antenna is in excellent agreement with the coaxial cable. At the points of "BB" impedance of about 60 ohms.

In the range of 21 MHz antenna length is slightly longer wavelength (L) of the range and reach the transformer is also a little longer than 3L / 4 matching any worse. Sizes do not allow you to work in a resonant mode, in spite of this antenna has a gain over a dipole is 1.8 dB, due to the fact that half the vibrator excited in phase. Diagram of the wire antenna in the same range as the two wave vibrator.

In the range of 14 MHz antenna matching is even worse than 21 MHz. At the points of "AA" very little resistance from the fact that the antenna has a size of 1.5L and is approximately 70 ohms. At these points there is a maximum current. Transforming line transforms the antenna impedance (70 ohms) to 200 ohms at points "BB". It is clear that such resistance is not suitable for connecting a coaxial cable with an impedance of 50 ohms ... 75. Reinforcement wire antenna in the range of about 2 - 2.2 dB.

In the range of 7 MHz G5RV wire antenna has a length 3L / 4 and the input impedance of 600 ohms. Length of transforming the line has 300 ohms resistance and the length of the 0.3L, as a result of the partial transformation of the 600 ohm resistance at the points of "AA" to the point "BB" is obtained impedance 150 ohm. Since the directional properties of the antenna wire in this range are similar pattern in a half-wave dipole and the win is no gain.

In the range of 3.6 MHz is a resonance antenna of its length in this range is 0.36 ... 0.47L. Antenna impedance is 150 ohms, the length of the transformer is equal to 0.15 ... 0.16L at points "BB" resistance is 100 ohm. In this range, the directional properties of even worse and the winning wire antenna gain, however.

From the above it follows that the written wire antenna (classical) English G5RV amateur radio should be used in conjunction with the tuner (for the transceiver). Changing the length of the line transformer and its impedance leads to improved coordination in some ranges and a deterioration in others.

### A Practical Antenna for 160 Metres

"This aerial is one I have used for top band (160 metres) - it was suggested to me by Alan G4ERZ, also of Hull.

It consists of 140 feet of insulated wire, the first half of which (70 feet) is space wound on an insulated tube.

• I used glass fibre tubing which was to hand, but PVC may be used also.
• My tube is 1 1/2 inches in diameter and about 5 feet 6 inches long.
• The turns are about 0.5 inches apart.
• The other 70 feet of wire acts as a loading wire and slope down from the top of the coil to near ground level.
• The system is coax fed to the base of the coil, with the shield or braiding going to earth.

It appears to work very well, apparently giving some horizontal and vertical polarisation.

One great advantage is the system can be tuned without having to lower the mast - by pruning the loading wire to resonate on the required part of the band.

Bandwidth is also good - mine is about 30 kHz either side of resonance.

I found the MFJ Antenna Analyzer MFJ-259 invaluable for this project, as well as many other experimental systems. Ensuring an efficient earth system will add to the effectiveness of the aerial I still have to improve my earth system, currently it consists of two 140 ft radials and connections to some buried guys stays.

Alan, G4ERZ, has a far more elaborate and efficient ground and his results prove what we all know - the ground (or earth system) is all important. He is a tremendous signal on 160 DX wise. He still gets the same band width as I do, though. I have worked a few DX stations with it since erecting it only a short while ago, and I think it has a lot to offer, especially for those of us blessed with relatively small gardens."

### A short dipole for 80 meters

The antenna above has been described by Nadisha, 4S7NR and may be of interest to anyone wishing to get on 80M (3.5MHz) that have limited space available.

L1 is 12 feet. L2 also is 12 feet and the overall length is 48 feet.

The two loading coils are described as 67.83uH and can consist of 104 turns of insulated wire, wound over 3.5 inches. The coil diameter is not stated however. Maybe it will be a case for experimentation here.

### An Inverted L for stealth with low(ish) visual impact

With a small back garden there is no way that I could accommodate an aerial for the 160m band that would be anything approaching full size. A full size dipole would be about 65 metres long and would need to be mounted at a very good height to be at its most effective. A full size vertical 1/4 wave would be about 37.5 meters tall. Impossible! Bending a 1/4 wave wire into an inverted L would still result in a very long wire - say 10 metres vertically and 27.5 metres horizontally. Still too large.

Full size top band antennas are big, far too big for my small plot, so I have tried a few different shortened 160m aerials. I really would prefer to use a balanced dipole not only for the radiation efficiency, but just as importantly for the lower noise on receive - like a ground mounted vertical aerial an inverted L can be rather noisy on RX. However I have to settle for a compromise, so shown in the drawings and photographs below is my current top band aerial, along with some previous experiments and ideas further down the page.
This incarnation of my Top Band aerial takes two forms. A compact Inverted L and, in its lower position, a less conspicuous sloping wire, shown below:

General layout of Top Band Aerial with fibreglass pole retracted to a height of 2 metres
Wire lengths are approximate: Inductor 5cm dia with approx 40 turns of 0.9mm e.c.w.

### Building a 2m quarter-wave ground-plane antenna

The first antenna that you should consider building is the quarter-wave ground-plane antenna for the 2m band. They are very easy to build and will perform better than the antennas that come with most handhelds.

The quarter-wavelength, ground plane antenna is made up of one vertical element, called the driven element, and four radials. The radials make up the ground plane. An easy way to make this antenna is to use an SO-239 coax connector. The driven element is soldered directly to the center conductor, while the four radials are connected to the four holes in the connector’s flange. See the figure at right.

A simple 2m antenna can be made with an SO-239 connector and four short pieces of stiff wire.

Now, let’s calculate how long the elements should be. Since the wavelength of a radio wave is equal to 300/f (MHz), one quarter wavelength will be equal to 75/f (MHz). At 146 MHz, therefore, the length of the driven element is:

75/146 = .51 m

In practice, we have to make one more adjustment. Because a radio wave travels more slowly in a wire than it does in free space, the wavelength will actually be about 5% less in a wire than in free space. So, we multiply the wavelength in free space by .95 to get the length of the driven element:

.51m x .95 = .49m = 19.25 inches

The radials should be about 5% longer than the driven element. This isn’t really very critical, so if you make them 20.25 inches long, the antenna will work just fine.

You should make the elements out of a stiff wire. 12 AWG copper wire will work for experimentation purposes. Welding rod might be better for a more permanent antenna.

You need to solder the 19.25-in. driven element to the solder cup of the center conductor of the SO-239 connector. Attach the radials to the holes in the flange of the SO-239 connector with nuts and bolts. You can also use these nuts and bolts to mount the antenna to some kind of bracket. Bend the radials out to a 45-degree angle, connect a coax cable to it, and start having fun!

### 40 METER LOOP ANTENNA

If one is interested mostly only on 40 meter working, he can think of a loop antenna. It is simple and at the same time very effective. For best results, it should be made as square as possible. It should not be made more rectangular as the efficiency will suffer. The overall length of the antenna in feet can be found out by the formula 1005/f MHz. For a resonant frequency of 7.05 MHz the total length of the wire will be 142 feet 6 inches. For antenna wire 16 or 14 SWG wire can be used. Use 75 Ohms co-axial cable for the transmission line. The antenna should be kept at a hight of about 6 feet from the ground level.

If vertical polarisation is desired, feed the loop in the center of the vertical sides. This will give low angle radiation. If one desires horizontal polarisation, feed either to the horizontal sides.

The directivity of the loop antenna is broadside from the loop. So the antenna may be hung in such a way for maximum direction. This loop antenna has 2 DB gain over the dipole. It works well on 20 and 15 meter also with compromising results. For an experimenter, it is an antenna worth giving a trial.

### Hentenna - An ADR Antenna

###### N. S. Harisankar / VU3NSH Tel : +91 491 2576102, 9895741932

Hentenna is designed in 1970s by Tadashi Okubo JH1FCZ, Someya JE1DEU. They are 6 meter hams in Japan. In Japan, the word HEN means 'interesting, unusual, strange' etc. Ofcourse, it is a strange antenna and it is an Asymmetrical Double Rectangle (ADR) Loop Antenna. This system has more gain than an ordinary square loop and has the less impedance (nearby 70 ohms). It has two loop sections L1 and L2. The L1 section is the radiator part and the L2 is forming for matching and it helps the low angle radiation (10 to 13 degrees). Refer QST-1982 Feb (by JJ1UMS) and ARRL Antenna compendium vol. 5.

It was described for the first time in QST magazine in February 1982 by Koji Sugihara JJ1UMS (Page No. 16 -17). This antenna will produce a 5.1 dBd gain and with a 1.3:1 SWR with an amazing band width of 6.5 MHz. It can be upto 10 MHz bandwidth with 2:1 SWR. I started this antenna project, for VHF operation, using 3/8th aluminium tube and with a fine feed point movable plate section. The plate I have taken was a plexi glass of 15" x 2" and of 6 mm thickness. A SO239 socket was fixed at the centre of this plate for the cable connectivity (Refer photographs). Both ends of the feeds are connected with the 12 mm x 12 mm and 20mm long aluminium solid blocks with screw fixing holes. A 1 mm brass road is used to connect the above block sections to the SO239 socket, as a feed line.

The Hentenna Asymmetric size combinations are ‘lambda by 2’, ‘lambda by 6’ rectangle and feed point is ‘lambda by 10’ approximately. This antenna is not an omni and it is a bidirectional type. The HEN Part (Strange or Interesting) is as follows; If this antenna is fixed horizontally then it will produce a vertical polarisation !!! If it is fixed vertically the polarisation will be in horizontal. This character is explained by F.C.Judd (G2BCX) in 2 m antenna handbook in the ‘stacked skeleton slot array’ (page number 89-92). i.e., “The vertical slot is horizontally polarised and vice versa”. The skeleton slot system was developed by B Sykes - G2HCG of J-Beams Ltd. The radiation pattern is just like peanut shell.

Fig. 1. Hentenna - Horizontally mounted vertically polarized

Fig. 2. Feed point section of hentenna

When firing the antenna for the first time with the SWR meter, I fixed the movable section to ‘lambda by 10’ approximately, then I moved it up and down and took the readings (see the SWR graph given below). Then I changed the feed point to get a very low SWR with low and high power. I got a beautiful match at 25 cm from inner surface of the right side tube (element - loop 2) and this point gives a 6.5 MHz bandwidth with a low SWR of 1.2:1 !!! at a low height of 4 feet inside my QTH, I got VU2KOD repeater as 5 5 and 5 6 and all local stations around 10 kms. as 5 9 plus 20 dB. I done this project three months back with a search of unusual antennas. For testing and assembling this antenna my SWL Rejeesh also helped a lot. Make this bi-directional asymmetric double rectangle loop antenna and enjoy...

Fig. 3. Hentenna - SWR analysed chart

Fig. 4. Hentenna - SWR analysed chart

Fig. 5. Bidirectional radiation pattern of vertically polarised 145 MHz hentenna

## Saturday, September 21, 2013

### vhf antenna 5 * 5

To increase the gain of the antenna needs to increase its size. Maximum gain depends on its construction . But if there is no possibility to install antennas with larger sizes in the UHF band can apply another method , you can place already with the existing VHF antenna has one just like it. Thus obtained one antenna system consisting of two separate VHF antennas. In this antenna system to produce phasing power and antenna impedance transformation and selection of the distance between them. This principle of the antenna system can be used to further increase the gain. Merging the two antennas in a single antenna system stacked designated - " 5 * 5 " . Such arrangement of the two VHF antenna narrows the directivity pattern in the vertical plane and this allows an increase of gain. Gain antenna system also depends on the distance between the antennas themselves . Generally omnibus two identical VHF antennas to one antenna system leads to an increase in gain of about 3 dB. Below is the diagram of the antenna system of two antennas for VHF 144 MHz . One of the antenna gain of about 6 dB and the antenna system of the two antennas about 9 dB. This antenna system is 5 * 5 and has enough broadband directional. Figure A) shows an antenna system with conventional cutting vibrators (2) , the input impedance of each of the antennas of 37.5 ohms, is used to align coaxial cable ( two segments ) long 3L / 4 and impedance of 75 ohms. As a result, the input impedance of each antenna at the point of connection of the power line is 150 ohms (the transformation of resistance) , and with two antennas , it is reduced to 75 ohms. In Figure B) an example of folded dipole antenna for VHF system. In this case, the antenna impedance is 150 ohms as line segments used matching wiring line length L / 2 . These segments do not transform the input impedance , while merging the two antennas in the input impedance at 75 ohms.
Dimensions of antennas in the antenna system :
Reflector (1): 1028 mm . Vibrator (2): 995 mm . Director (3,4,5) : 927 , 914 , 914 mm .
Distances: Reflector - Vibrator(6-7) : 380 mm . Vibrator - Director(6-7): 508mm . The distance between the other directors ( 7-8-9 ) 508 mm .
The distance between the antennas of 1220 mm .

## Saturday, September 14, 2013

### vertical antenna for the 144-146 MHz range with 5.6 dB gain

As is known usual vertical dipole is omnidirectional in a vertical plane. A simple antenna with omni-directional (vertical dipole) , for all its simplicity of design has a significant drawback - low gain . In order to overcome this drawback has been developed vertical collinear antenna has more gain than conventional vertical antenna with gain 5.4 dB. Image vertical antenna gain is due to the restriction pattern in the vertical plane, the radiation pattern in the horizontal plane of the antenna remains the same round. Vertical antenna with omni-directional gain 5.4 dB and its dimensions in millimeters shown in the figure. The antenna is designed to operate in the 144-146 MHz amateur band . The vertical antenna can be performed on the wooden pole or the other insulating material. Since the connection point of the power line vertical antenna has a high input resistance of about ( 500 ohm ) , you need to connect a coaxial cable to a transformer or a quarter-wave impedance transformer is made ​​of an air line with its own impedance Z = 330 ... 390 ohms. The right figure shows how to perform phasing line segments , the turns around the mast antenna diameter of 160 mm .

## Saturday, August 31, 2013

### antenna in the form of a long wire and a matching device for her

It is commonly assumed that the length of the antenna to be resonant at the connection to the antenna feed line should be only reactive component of the resistance. This condition can soften or simply ignored if used simple wire antenna (in the form of a long wire ) . A simple wire antenna can be seen as a modernized antenna "L -type " , but there are differences - the length of a wire antenna can be chosen arbitrary , as well as the need for a grounding system . Wire antenna with an arbitrary length can handle the entire range of the HF bands, some bands antenna will have repercussions in the other will have to reckon with the reactive component of the input impedance . If a wire antenna to connect a coaxial cable , you must use a transformer resistance , to take measures to compensate for the reactance . Diagram of a complex shape and is close to the antenna radiation pattern of harmonic in some areas will have an asymmetrical shape. To work in a multi-band wire antenna should have a matching device . And to improve the characteristics of the antenna wire requires the use of special earthing system (Figure) . The length of wire grounding wire antenna must comply with the wavelength at which the antenna is working , it is advisable to use two wires. One wire should pass under the antenna and the other at the other end . The wires may be arranged on the surface or buried to a depth of 20 centimeters. To match the wire antenna with a coaxial cable can be used for matching devices shown in the figures below. If the input impedance of the antenna wire is less than or equal to the resistance of the cable you need to use the first pattern matching device if more then a second picture of the matching device. In the second picture below 4:1 transformer used .

## Saturday, August 17, 2013

### aperiodic ferrite baluns for harmonization antennas

For balancing and harmonizing Ham antennas can be used aperiodic ferrite baluns. These devices can operate in the Amateur Radio HF and VHF bands. These aperiodic balun on their wires occur with the same high-frequency currents in the opposite direction, resulting in a ferrite core simmeriruyuschego devices resulting magnetic field is zero. If the load (antenna) that there is an asymmetry in the ferrite appears not compensated magnetic flux. Depending on the size of the ferrite core and the wire cross-section aperiodic balun can be used on the transmitter power is a few milliwatts to several kilowatts. To match the antenna can be used by various schemes aperiodic ferrite baluns. The following figures show these schemes.
This figure shows a diagram of a balun with crown windings, it does not produce the transformation of input and output impedance. One of the windings is needed to improve the characteristics of the ferrite balun in the range of 28 MHz amateur radio. The two windings are wound bifilar and one separately.

For balancing and alignment of antennas with a high input impedance can be used a second-figure, in this scheme, the transformation of the input and output resistance by a factor of 1:4. In order to be symmetry was in all the bands to perform the winding so that would be between the wires was a small and constant distance along the winding. This scheme provides a good agreement with a coaxial cable with an impedance of 50 ohms ... 75.

For balancing and alignment of antennas with low resistance can apply an apparatus as shown in the figure. The input impedance of the antenna may be approximately 20 ohms. The transformation ratio 4:1 zeal.

To change the transformation ratio of the ferrite aperiodic balun can apply this scheme. The transformation ratio can be varied from 1:4 to 1:10

If you need to agree on an asymmetrical antenna and asymmetric power line that is now such a scheme, with a ratio of 4:1.

This scheme is applied on a ferrite ring if necessary to carry out a phase shift of 180 degrees in an unbalanced line.

Ferrite matching devices do not make a large attenuation in the antenna gain and is resistant to momentary overloads.

## Saturday, August 10, 2013

### matching network for the antenna feed line

To match the output stage of the transmitter antenna to the power line, you can use proprietary matching devices for example mfj. But if you do not have or can not buy it, then you can build a device to align antennas shown in the figure. This is a matching device used to adapt the output of the transmitter with a resistance of 50 ohms with balanced and unbalanced power line connected to the antenna input impedance from 10 to 4000 ohms. Between the transmitter output and the input matching device placed SWR. After SWR transmitter signal applied to the input matching circuit devices for L1-C1 (L1A-C1, L1B-C1) which has inductive coupling with the antenna circuit. Setting the Loop L1-C1 made pripomoschi capacitor C1. Setting the antenna circuit L2-C2 (L2AB-C2C3) made capacitors C2 and C3. By the antenna circuit may be connected balanced or unbalanced load. The adjustment is made independent of each other capacitors C2 and C3. Switch matching device has four sections at five positions (or more depending on the number of bands). Coils L1A and L1B has four turns in the range of 80 and 40 meters, both coils are connected in series (8 turns), other bands parallel. Parallel connection improves the agreement with the 50 ohm output of the transmitter. All coils are wound on a device matching the same frame having a diameter of 75 mm. Coils L2A and L2B are approximately 28-30 turns. Since capacitors matching device are under a lot of stress, they must be isolated from each other and from the metal housing of the device, the handle on the axes of the capacitors should also be insulated. The second figure shows the performance of the matching coil unit.

## Sunday, August 4, 2013

### two cell antenna delta for 40 meters

The first figure shows a conventional antenna Delta with dimensions for a range of 40 meters. The size of the delta can be calculated by the formula L = 304 / F: L - perimeter of the delta, F - frequency at which it is set. At the point of connection of the coaxial cable included tuning loop length of 80 centimeters. Setting the delta is produced by this train on a minimum SWR. The antenna radiates perpendicularly to the antenna plane. Increase the gain of the delta can be placed at a distance L / 4 from the existing framework of another of the same frame of the same length. Delta gain increases due to the fact that one performs the role of the delta frame vibrator and the other reflector (second figure), i.e. the antenna is unidirectional. In order to change the direction of emission of the delta to the framework necessary to connect an additional antenna loop length L / 4 from the same coaxial cable, and set the switch (third picture). Cable length of frames to loop can be arbitrary. This antenna system can operate only on one range. Strengthening the double delta of about 7 dB. For a more exact matching antenna tuner is needed.
The distance between the borders of the delta in meters:
28 MHz - 2.65
21 MHz - 3.54
14 MHz - 5.32
7 MHz - 10.64
3.6 MHz - 20.2
Loop length in meters:
28 MHz - 1.75
21 MHz - 2.34
14 MHz - 3.52
7 MHz - 7.02
3.6 MHz - 13.33
(Dimensions loop length for the cable impedance of 75 ohms for the other cables needed and stored in the velocity factor.)

## Saturday, February 2, 2013

### Space Solar Power

The United States and the world need to find new sources of clean energy. Space Solar Power gathers energy from sunlight in space and transmits it wirelessly to Earth. Space solar power can solve our energy and greenhouse gas emissions problems. Not just help, not just take a step in the right direction, but solve. Space solar power can provide large quantities of energy to each and every person on Earth with very little environmental impact.

The solar energy available in space is literally billions of times greater than we use today. The lifetime of the sun is an estimated 4-5 billion years, making space solar power a truly long-term energy solution. As Earth receives only one part in 2.3 billion of the Sun's output, space solar power is by far the largest potential energy source available, dwarfing all others combined. Solar energy is routinely used on nearly all spacecraft today. This technology on a larger scale, combined with already demonstrated wireless power transmission (see 2-minute video of demo), can supply nearly all the electrical needs of our planet.

Another need is to move away from fossil fuels for our transportation system. While electricity powers few vehicles today, hybrids will soon evolve into plug-in hybrids which can use electric energy from the grid. As batteries, super-capacitors, and fuel cells improve, the gasoline engine will gradually play a smaller and smaller role in transportation — but only if we can generate the enormous quantities of electrical energy we need. It doesn't help to remove fossil fuels from vehicles if you just turn around and use fossil fuels again to generate the electricity to power those vehicles. Space solar power can provide the needed clean power for any future electric transportation system.

While all viable energy options should be pursued with vigor, space solar power has a number of substantial advantages over other energy sources.

• Unlike oil, gas, ethanol, and coal plants, space solar power does not emit greenhouse gases.

• Unlike coal and nuclear plants, space solar power does not compete for or depend upon increasingly scarce fresh water resources.

• Unlike bio-ethanol or bio-diesel, space solar power does not compete for increasingly valuable farm land or depend on natural-gas-derived fertilizer. Food can continue to be a major export instead of a fuel provider.

• Unlike nuclear power plants, space solar power will not produce hazardous waste, which needs to be stored and guarded for hundreds of years.

• Unlike terrestrial solar and wind power plants, space solar power is available 24 hours a day, 7 days a week, in huge quantities. It works regardless of cloud cover, daylight, or wind speed.

• Unlike nuclear power plants, space solar power does not provide easy targets for terrorists.

• Unlike coal and nuclear fuels, space solar power does not require environmentally problematic mining operations.

• Space solar power will provide true energy independence for the nations that develop it, eliminating a major source of national competition for limited Earth-based energy resources.

• Space solar power will not require dependence on unstable or hostile foreign oil providers to meet energy needs, enabling us to expend resources in other ways.

• Space solar power can be exported to virtually any place in the world, and its energy can be converted for local needs — such as manufacture of methanol for use in places like rural India where there are no electric power grids. Space solar power can also be used for desalination of sea water.

• Space solar power can take advantage of our current and historic investment in aerospace expertise to expand employment opportunities in solving the difficult problems of energy security and climate change.

• Space solar power can provide a market large enough to develop the low-cost space transportation system that is required for its deployment. This, in turn, will also bring the resources of the solar system within economic reach.

• High development cost. Yes, space solar power development costs will be very large, although much smaller than American military presence in the Persian Gulf or the costs of global warming, climate change, or carbon sequestration. The cost of space solar power development always needs to be compared to the cost of not developing space solar power.

Requirements for Space Solar Power

The technologies and infrastructure required to make space solar power feasible include:

• Low-cost, environmentally-friendly launch vehicles. Current launch vehicles are too expensive, and at high launch rates may pose atmospheric pollution problems of their own. Cheaper, cleaner launch vehicles are needed.

• Large scale in-orbit construction and operations. To gather massive quantities of energy, solar power satellites must be large, far larger than the International Space Station (ISS), the largest spacecraft built to date. Fortunately, solar power satellites will be simpler than the ISS as they will consist of many identical parts.

• Power transmission. A relatively small effort is also necessary to assess how to best transmit power from satellites to the Earth’s surface with minimal environmental impact.

All of these technologies are reasonably near-term and have multiple attractive approaches. However, a great deal of work is needed to bring them to practical fruition. In the longer term, with sufficient investments in space infrastructure, space solar power can be built from materials from space. The full environmental benefits of space solar power derive from doing most of the work outside of Earth's biosphere. With materials extraction from the Moon or near-Earth asteroids, and space-based manufacture of components, space solar power would have essentially zero terrestrial environmental impact. Only the energy receivers need be built on Earth. Source: www.nss.org