Large loop antennas

There are two basic classes of loop antennas: small loops and large loops.

The small loop antenna has an overall length that is less than about 0.18 lambda.

Large loop antennas, on the other hand, have overall lengths larger than 0.5 lambda, and some of them are two or more wavelengths. The small loops are used for radio direction finding and for certain AM broadcast band reception problems. The topic of this Section is the large loop antenna, of which several varieties for both transmitting and receiving are covered. We will also look at some in-between size loops that I have dubbed 'smaller large loops' to distinguish them from small radio direction finding loops.

QUAD LOOPS

The quad loop antenna ( FIG. 1) is perhaps the most effective and efficient of the large loop antennas, and it’s certainly the most popular.

The quad loop consists of a one wavelength loop of wire formed into a square shape. It provides about 2 dB gain over a dipole. The views in FIG. 1 are from the horizontal perspective looking at the broad side of the loop. The azimuthal radiation pattern is a figure '8', like a dipole, with the directivity in and out of the page.

The quad loop can be fed in either of two ways. FIG. 1A shows the feed attached to the bottom wire segment, and this produces horizontal polarization. The same polarization occurs if the feedpoint is in the top horizontal segment. If the feed is in either vertical segment ( FIG. 1B) then the polarization will be vertical.

FIG. 1

FIG. 2

The elevation pattern is shown in FIG. 2. This pattern is found when the top horizontal segment of the loop is quarter wavelength from the ground. The directivity is in and out of the page. Note that there are two sets of lobes, one horizontally polarized (a minor lobe) and two vertically polarized. These lobes are derived by taking a slice out of the three-dimensional pattern that would be seen as a figure '8' pattern from above.

The overall length of the wire used to make the loop is found from:

L_meters = 306:4 F_MHz meter

Examples of wire lengths for loops of various frequencies are given in TBL.1. Each side is one-fourth of the total wire length.

There are several methods for constructing the quad loop. If you want a fixed loop, then it can be suspended from insulators and ropes from convenient support structures (tree, mast, roof of a building).

If you want to make the loop rotatable, then use a construction method similar to that of FIG. 3A. This method uses a plywood gusset plate, approximately 30 cm square, to support a set of four spreaders. The gusset plate can be attached to a mounting pole or rotator pole with U-bolt clamps. Details of the gusset plate construction are shown in FIG. 3B.

The four spreaders are held to the gusset plate with two to four small U bolts. The gusset plate is held to the mounting mast with two or three large U-bolts. In both cases, be sure to use a substantial size U-bolt in order to prevent breakage (use stainless steel wherever possible).

The spreaders can be made of wooden dowels at very high frequency (VHF). I have even seen larger cylindrical wooden dowels (2-3 cm diameter) used for quad loops in the upper end of the HF spectrum. For all other HF regions, however, you can buy fiberglass spreader specially manufactured for the purpose of building quad loops or quad beams. At one time, it was popular to build the quad loops from bamboo stalks. These were used as the core on which carpet was rolled, and carpet dealers would sell them for a modest price or even give them away. Today, however, carpet manufacturers use hard cardboard tubes for the roller, and these are unsuitable for building quad loops. Bamboo stalks of the right size (2.5-4m) have all but disappeared from the marketplace.

The quad loop can be fed with coaxial cable, although it’s a good idea to use a 1:1 BALUN transformer at the feedpoint if only coaxial cable is used.

The impedance match is not exact, and a voltage standing wave ratio (VSWR) will be found. The feedpoint impedance is of the order of 100 ohms, so the VSWR when 75 ohm coaxial cable is used is only 100/75, or 1.33:1. Some people use a coaxial cable impedance matching stub between the quad loop feedpoint and the coaxial cable to the rig or receiver. Such a stub, called a Q-section, is made of 75 ohm coaxial cable, and is a quarter wavelength long. The coaxial cable to the rig or the receiver in that case is of 52 ohms.

To make an electrical quarter-wavelength matching stub you must shorten the physical length by the value of the velocity factor of the coaxial cable used for the matching section. For example, suppose we are building a quad loop for 14.25MHz. A quarter wavelength in free space is 75=14:25 = 5:26m. But if polythene dielectric coaxial cable (velocity factor (VF)= 0:66) is used, the physical length required to make an electrical quarter wavelength is 5:26m _ 0:66 = 3:472m. If poly-foam dielectric coaxial cable (VF = 0:82) is used for the matching section, then the required physical length is 4.31 m.

TBL.1

FIG. 3

QUAD LOOP BEAMS

The basic quad loop is bidirectional ( figure '8' pattern). If you want to make the loop unidirectional, it can be built into a beam antenna by adding a second loop as either a reflector ( FIG. 4A) or director ( FIG. 4B). The reflector and director elements are not directly excited by the transmitter, and are therefore called parasitic elements. The reflector is slightly larger than the main loop (called the driven element), while the director is slightly smaller. The overall wire sizes are found from:

Reflector:

LRef = 315 F_MHz meters

Driven element:

LDE = 306 F_MHz meters

Director:

LDir = 297 F_MHz meters

Spacing between elements:

S = 60 F_MHz meters

FIG. 4

The directivity of the two-loop beam is always in the direction of the smallest element, as seen by the arrows in FIG. 4, and the forward gain will be about 7 dBd (9.1 dBi), while the front-to-back ratio will be up to 25 dB (the actual value depends on the spacing of the elements).

The quad loop beam has a tradition that goes back to just before World War II. The missionary short-wave radio station HCJB in Quito, Ecuador was experiencing problems with its Yagi beam antennas. There was a constant corona discharge off the ends of the elements because the tips are high voltage points. At lower altitudes than Quito's Andes location, these antennas don’t exhibit the problem, but at altitude the arcing was severe enough to create a constant (and expensive) maintenance problem for the engineers.

They invented the quad beam to solve the problem. The reason is that the feed method puts the high-voltage nodes in the middle of the vertical segments. It takes a much higher voltage to cause corona arcing from the middle of a cylindrical conductor than off the ends, so the problem was eliminated.

Ham operators and some commercial stations quickly picked up on the quad beam because it offered a relatively low-cost method for obtaining directivity and gain. In addition, the quad beam is believed to work better than the Yagi beam in installations that are close to the Earth's surface (e.g. less than a half wavelength).

The quad antennas shown here are two-element designs. Three and more elements can be accommodated by using both a reflector and a director, or any combination of multiple directors or reflectors. It’s common practice (but by no means totally necessary) to use one reflector and as many directors as are needed to accomplish the desired number of elements. Each element added to the array will increase the gain and narrow directivity. The feedpoint impedance is around 60 ohms, so it makes a reasonably good impedance match to both 52 and 75 ohm coaxial cable.

DELTA LOOPS

The delta loop ( FIG. 5) gets its name from the fact that its triangular shape resembles the upper-case Greek letter delta (Δ). These three-sided loops are made with a full-wavelength piece of wire, each side of the equilateral triangle being one-third wavelength long.

Three different feed schemes are shown in FIG. 5, but all three of them attach the feedline at an apex of the triangle. The antenna in FIG. 5A is fed at the top apex, that in FIG. 5B is fed at bottom apex, while that in FIG. 5C is fed at one of the side apexes (either right or left could be used).

The overall length (in meters) of the wire used to make the delta loop is found from 306.4/F_MHz only if the antenna is mounted far enough from the ground and surrounding objects to simulate the elusive 'free space' ideal. But for practical delta loops a nearer approximation is found from 285/F_MHz. The actual size will be between the two values.

A delta loop built for 9.75MHz is shown in FIG. 6. The overall formula length of the wire is 29.23m, with each side being 9.74m. The transmission line to the rig or receiver is 52 ohm coaxial cable. There is a coaxial quarter-wavelength impedance matching section ('Q-section') between the antenna feedpoint and the line to the receiver or rig. The Q-section is made from 75 ohm coaxial cable.

FIG. 5

The physical length of the Q-section is reduced from the free space quarter wavelength (75/F_MHz m) by the VF, to (75 _ VF)/F_MHz m. At 9.75MHz, if polythene coaxial cable is used (VF = 0:66) the length of the section is 5.1m, but if polyfoam coaxial cable (VF = 0.82), then it’s 6.3m.

FIG. 6

'ON-THE-CHEAP' ROOM LOOP

There are many situations where short-wave antennas cannot be installed without great pain and suffering, or where landlords, building managers, and other sundry unsympathetic types refuse to permit outdoor antennas. If you have a wall inside the building that will allow erection of a normal quad loop (as shown above), then there is no reason why you cannot attempt it (unless you are inside a metal frame or metal sided building!). I have seen cases where ham operators running relatively low-power levels (50-100W) used full-wave quad loops mounted on the wall from floor to ceiling. In fact, one fellow sent me a photo of his installation where there were two adjacent quad loops on two walls that were at right angles to each other. By feeding them both along the vertical edge in the corner he was able to switch directions with a simple double-pole double-throw (DPDT) heavy duty switch. It seemed like a good solution for anyone who finds messy wire an acceptable wall decoration.

Another solution is to use a room loop antenna such as that in FIG. 7.

Although shown here as a horizontal delta loop, it can also be square or rectangular. The 'on-the-cheap' room loop is mounted on the ceiling of the room. The wire can be suspended from the type of hooks used to hang planters and flower pots. I have even seen cases where the sort of hooks used to mount pictures on the walls were used on the ceiling to support the antenna wire.

The loop size is adjusted to fit the room, and is essentially a random length as far as any particular frequency is concerned. The feedline is 300 ohm, 450 ohm or parallel open feedline run vertically down the wall at the operating position to a balanced antenna tuning unit.

This antenna works well for receiving sites, and can be used for low powered transmitters, but it should not be used for higher power transmit ting. Also, it’s probably prudent to use insulated wire for the antenna element.

FIG. 7

INDOOR 'MIDDLE-EAST ROOM LOOP' ANTENNAS

There are many reasons why someone might want to build a room loop antenna. For some people, the problem is one of unsympathetic landlords, while in other situations there are problems in the layout of the property that limit antennas. In the USA, most new housing developments impose legally binding restrictive covenants that forbid the use of outdoor antennas on the deeds of houses sold. In some countries, short-wave radio antennas are limited because of political considerations. The antenna design in FIG. 8 was sent to me via one of my magazine columns by a reader in a Middle-Eastern country that severely restricts both external antennas and the bands which short-wave receivers can pick up. He is limited to models that receive 4-7MHz in addition to only a 200 kHz portion of the AM broadcast band and a 2MHz segment of the FM broadcast band (what paranoia those politicians must have!). He also felt that it was necessary to not call attention to himself by erecting the short permitted outdoor antennas because, as a foreign worker, he is already somewhat suspect, and believed that a substantial external antenna might label him as some sort of intelligence agent.

He claimed that this antenna worked quite well. The loop consists of 30-40m of insulated wire (e.g. No. 22 hook-up wire) wound around the room to form three or four loops (the figure assumes a square room). My correspondent mounted the loop at the intersection of the ceiling and the walls. The windings were closely wound with little or no spacing between the windings.

The chap who sent me this design used an antenna tuner consisting of a shunt 365 pF broadcast variable and a 28 mH series inductor (i.e. a classic L section tuner of the sort used by many radio amateurs and short-wave listeners). From some of my experiences during my student days (when I lived in student boarding house rooms), the antenna tuner might be purely optional for receiver operators. Try connecting your receiver directly to the loop using ordinary coaxial cable.

FIG. 8

If you have some means for measuring the antenna impedance or VSWR, then make the measurement for the frequencies of interest before commit ting yourself to building or buying a tuner. Another option that will eliminate the antenna tuner, especially if you confine the use of the antenna to a small segment of the HF spectrum, is to use a BALUN or other form of impedance transformer at the feedpoint. This option becomes less viable as the frequency coverage required increases because the feedpoint impedance will vary all over the place with changes in frequency.

I cannot as yet recommend this antenna for transmitting above the purely QRP level (a few watts), so don’t try it except at your own risk.

The directivity of this antenna is a bit uncertain because it will change with frequency. I found no problems using similar loops in my boarding house room, but common sense suggests that the azimuthal and elevation patterns will be quite different at the various bands throughout the HF short-wave bands.

A MULTIBAND SWITCHABLE DELTA LOOP

Wire antennas are among my favorites because they are low cost, reasonably well behaved, and can easily be erected and then torn down as the experimenting urge hits. Alternatively, if the urge to experiment is not something that hits you very often, or if you prudently lay down and let it pass when it does, then wire antennas are still (normally) easy to erect and are reasonably robust against the elements. They last a long time with reasonable maintenance. As might be expected of a guide that deals with wire antennas, we take a look at quite a few different wire antennas. This time, we are going to look at two multiband delta loop antennas based on both the G4ABS and the N4PC designs. These antennas produce gains of the order of 4-8 dB, depending on the band of operation.

Multiband Loop 1

The first loop antenna works on 3.5, 7, 14 and 28 MHz, and is constructed of No. 14 antenna wire and a 10m piece of either 300 or 450 ohm twin-lead transmission line. With slight modification, it will also work on a series of bands starting at 5MHz and proceeding up through the HF short-wave band.

FIG. 9A shows the multiband delta loop antenna design. There are four sections to this antenna. Two sloping side sections are made of No. 14 antenna wire, and are 10m long. The top section is 9.75m of No. 14 antenna wire, but is cut in the center to form two equal-length sections. Hanging from the center of the top section is a vertical section made of twin-lead transmission line (10m).

FIG. 9

To make this antenna work on the international short-wave bands rather than the ham bands, multiply these dimensions by 0.7. This is an example of dimensions scaling. It can be done by taking the ratio of the frequencies, and multiplying the resultant factor by the lengths. Scaling only works if all of the lengths are treated in this manner.

The two sloping side sections and the vertical section are brought to a connector board made of an insulating material such as ceramic, Plexiglas or even dry wood (if it can be kept dry and low power levels are used). We will take a look at the connection schemes for the different bands in a moment.

The antenna is supported in a manner similar to a dipole or any other wire antenna. The cut at the center of the top section, with its connections to the vertical section, are supported by an end insulator. The ends of the top half sections are supported by end insulators and ropes to nearby structures, just like a dipole. In some cases, a 10m or higher wooden mast might be used to support the center of the top section. In that case, the vertical section can be tied to it, improving its mechanical support. In addition, the connections board (used for band changing) can be mounted close to its base.

FIG. 9B shows the connections scheme to make the antenna work on the four different bands (which, you will undoubtedly notice are the harmonically related HF bands). All connections go to stand-off insulators, labeled A, B, C, D, E, and F. The cheapest way to use these connection points is to manually connect a shorting wire between the appropriate terminals. People with a bit more money to spend might want to get some coaxial relays, radio frequency relays, or vacuum relays in order to perform the switching. For receiver and very low-power transmitter applications, the connectors can be five-way binding posts that accept a banana plug. The shorting could be done with short (very short!) pieces of wire tipped at each end with the banana plugs. The connections scheme is as follows:

(1) To make the antenna work on the 75/80m bands (3.5-4.0 MHz), short B-C, A-E, and D-F.

(2) To make the antenna work on 40m (7.0-7.3 MHz), short B-A-E and C-D-F.

(3) To make the antenna work on 20m (14.0-14.35 MHz), short B-E and C-F.

(4) To make the antenna work on 10m (28.0-29.7 MHz) short A-E and B-F.

My impression of the multiband delta loop is that it works about as well as a dipole, and is generally bidirectional. However, the pattern does seem to change considerably from band to band (which is to be expected). I don’t want to say much about how it changes because propagation effects are so different on the four bands that it would take a very long time of observing signals to get a good idea of what the pattern looks like. Any statement about patterns, other than it appears to change from band to band, would be unwise without extensive modeling or some actual measurements.

Multiband Loop 2

The other form of multiband loop is shown in FIG. 9C. This design uses a full-wave loop with the balanced feedline connected at one of the apexes of the triangle, and a quarter-wavelength stub. Both the stub length and the overall length (L ) L2 ) L3) are calculated at the highest frequency of operation. It will operate over three bands that are harmonically related (e.g. 3.5/7.0/14.0 MHz, or 5/10/15MHz, etc.). The overall length in meters is found from (L1 ) L2 ) L3) = 615/F_MHz, while the stub is 60/F_MHz (assuming that the usual form of twin-lead is used, which has a VF of 0.82). Both of these antennas produce patterns broadside from the loop plane, although both the azimuthal and elevation radiation patterns vary from one band to another.

DOUBLE-DELTA LOOP

The double-delta loop antenna ( FIG. 10) consists of a back-to-back pair of large horizontal delta loops fed 1808 out of phase with each other. The view shown is a plan view, i.e. as seen from above. The far corners of the two delta loops are connected together by a 1808 phase-reversing harness made from a length of 450 ohm twin-lead or parallel ladder line. The 1808 phase reversal is achieved by twisting the twin-lead over on itself once (and only once).

FIG. 10

The feedline to the receiver or its antenna coupler is another piece of 450 ohm twin-lead connected to the mid-points of the two conductors of the 1808 phasing harness. This transmission line will make a decent if not perfect match to receivers that have a balanced input. Use of a 4:1 BALUN transformer at the feedpoint will drop the impedance to about 112 ohms, which is not too bad a match for 75 ohm coaxial cable. On the other hand, if you want a near-perfect match, then opt instead for a 9:1 BALUN transformer and connect the receiver using 52 ohm coaxial cable. There are several forms of 9:1 BALUN transformer on the market, but are sometimes hard to find except by mail order. If such a transformer is not available, then you will have to build it yourself (which is not too great a chore).

The length of each of the four sides of the double-delta loop is about a quarter wavelength, and is found from

A = 66 F_MHz meters

Let us look at some examples: a 60m band antenna cut for 5MHz and a 31m band antenna cut for 9.75MHz (assume I did the arithmetic on my calculator, with the results tabulated below):

F (MHz) Meters 5.00 13.20 9.75 6.77

The delta loop antenna is well regarded because it performs similarly to the quad loop, but is somewhat easier to install when the site only has a single high point. A friend of mine in Ireland uses a tall tower for his 20m beam antenna. The tower becomes the upper support for a 75/80m delta loop made of wire.

SMALLER LARGE LOOPS

The loops in this section are physically smaller than the one-wavelength loops of the previous sections. Few of them will work as well as the full size loops, but they will work passably well, and can be installed at sites that won’t accommodate the larger variety. I call them 'smaller large loops' to distinguish them from the small loops used in radio direction finding.

Half-wavelength loop

The half-wavelength loop is j/8 on each side, and is one-half the size of the full-wavelength quad loop discussed earlier. There are two configurations for this loop. The closed-loop version ( FIG. 11A) transmits and receives in the direction opposite the feedpoint, while the open-loop variety ( FIG. 11B) transmits and receives in the opposite direction.

FIG. 11

The two half-wavelength loops differ not just in the direction of radiation but also in the feedpoint impedance. The antenna in FIG. 11A (closed loop version) is fed at a voltage node, while the current node is in the middle of the opposite segment. As a result, the feedpoint impedance is several kilo ohms. This means that a matching stub, impedance transformer or some other means of reducing the impedance is necessary. The open-loop variety ( FIG. 11B) forces the current to be a minimum at the open-circuit point, which means that the current maximum (and voltage minimum) occurs at the feedpoint. The open-loop version can be directly fed with coaxial cable.

These antennas are lossy, so have a poor front-to-back ratio (_6 dB) and no gain over a dipole. Indeed, the gain is _1 dBd. Of course, if you want to make it seem like a better antenna, then quote the gain over isotropic, which is about )1.1 dBi.

Inductor-loaded smaller large loop

FIG. 12A shows a less-than-full-size loop that is inductively loaded to lower the resonant point. The overall length of the wire used to form the loop is found from:

A = 180 F_MHz meters

Each side is one-fourth this length. Note that the loop is a bit larger than a half wavelength.

The inductor should have a reactance of about 2500 ohms at the frequency in the middle of the band of operation. For example, if you build the antenna for reception in the 31m band (e.g. 9.75MHz), then the overall length of the antenna is 180/9.75 = 18.46m, and each side is 4.62m long.

FIG. 12

The coil inductance required can be found from:

L_mH = 400 F_MHz micro-henrys

For the 9.75MHz example antenna, the value of the inductance required is (400/9.75MHz) = 41 mH:

For receiver sites, the inductor can be a small toroid core coil. For example, if the 2.5 cm red core T-106-2 is used, then 55 turns of small diameter wire are required to make the inductor.

The antenna is not recommended for transmitting above the lowest power levels. Even at modest power levels (e.g. 100W), a solenoid wound air core coil should be of the order of 4-5 cm diameter with wire in the No. 14 size.

The antenna is fed at the mid-point of the side opposite the inductor. A 1:1 BALUN transformer is used to interface the feedpoint to 52 or 75 ohm coaxial cable.

A variation on the theme is the half-wavelength loop shown in FIG. 12B. It’s a tad smaller than the previous inductor load loop. In this case, the inductance is split into two inductors, and are placed at the mid-points of the segments adjacent to the segment containing the feedpoint. The coils in this variety should have a reactance of 360 ohms, making the inductance:

L_mH = 57 F_MHz micro-henrys

Both of these antennas can be used in a beam array by placing two identical loops facing each other ( FIG. 7C), and separated by a spacing of:

S_meters = 33 F_MHz meters

The two antennas are fed in-phase, so there are two methods of attaching the transmission line. If you want to use parallel line or 450 ohm twin-lead, then connect the phasing harness straight across and connect the transmission line to the mid-point. But if you wish to use coaxial cable, then feed the antenna as shown in FIG. 7C, using a 1:1 BALUN transformer. The 450 ohm twin-lead phasing harness between the elements should be twisted over on itself once, as shown.

The diamond loop

The diamond loop antenna is shown in FIG. 13. This antenna is a shortened, flattened quad loop consisting of two equilateral triangles back to back. The length of each side, plus the height (dashed line) of the two principal apexes, is found from

L_meters = 70 F_MHz meters

FIG. 13

FIG. 14

In order to feed this antenna with coaxial cable, a 4:1 BALUN transformer is used between the coaxial cable and the feedpoint of the antenna.

Half-delta loop

The antenna in FIG. 14 achieves a smaller size by being grounded. It’s essentially one-half of a full-wave delta loop, with the other half being 'imaged' in the ground. The wire forms a right triangle, with the vertical section being j/6 and the sloping section being j/3. These lengths are found from j 3 = 102 F_MHz meters and j 6 = 61 F_MHz meters

The antenna is inherently unbalanced with respect to ground, so can be fed directly with 52 ohm coaxial cable.

Two-band compact loop Most of the loops discussed thus far are basically mono-banders, unless multiple loops are built on the same frame and fed in parallel. The loop in FIG. 15, however, operates on two bands that are harmonically related to each other. For example, if FL is the lower band, and FH is the higher band, then FH = 2 _ FL.

The overall length of the loop is a half wavelength, but it’s arranged not into a square but rather into a rectangle in which the horizontal sides are twice as long as the vertical sides, i.e. the horizontal elements are a quarter wavelength and the vertical sections are one-eighth wavelength. The section lengths are

Horizontal:

Lhor = 75 F_MHz meters

Vertical:

Lver = 37:5 F_MHz meters

In both equations, the frequency is the center frequency of the lower band of operation.

The vertical stub is made of 600 ohm parallel open-wire transmission line, although 450 ohm twin-lead could also be used. The length of the stub is found from the same equation (above) as the vertical segment if open-wire line is used. If twin-lead is used, then multiply that distance by the velocity factor of the transmission line.

The coaxial line is a Q-section made of 75 ohm transmission line. It’s cut to a quarter wavelength of the upper band, i.e. twice F_MHz used in the calculations above.

FIG. 15

THE BI-SQUARE REALLY LARGE LOOP

The bi-square loop in FIG. 16 is twice as large as the quad loop discussed earlier in this Section. The overall length of the wire is two wavelengths, so each side is a half wavelength long. The overall length is calculated from

L_meters = 585 F_MHz meters

While each side is:

L_meters = 146:25 F_MHz meters

The bi-square antenna can be used on its design frequency, and also at one-half of its design frequency (although the patterns change). At the design frequency, the azimuthal pattern is a clover leaf perpendicular to the plane of the loop, and is horizontally polarized. At one-half the design frequency the radiation is vertically polarized, and the directivity is end fire.

FIG. 16

VHF/UHF QUAD BEAM ANTENNA

FIG. 17 shows a VHF/UHF quad beam with four elements. Although it's technically possible to build such a beam for a lower frequency than VHF, it’s not too practical because of mechanical considerations. But at VHF and UHF frequencies the dimensions of the elements become less large, and therefore more manageable. These dimensions are:

Reflector:

LREF = 31 500 F_MHz cm

Driven element:

LDE = 30 600 F_MHz cm

Directors:

LDIR = 29 700 F_MHz cm

Spacing between elements:

S = 6000 F_MHz cm

Where all elements lengths are in centimeters (cm).

FIG. 17

The antenna can be made of thin or thick wire. In the thin wire (#10 through #18) version, a support such as FIG. 3 is needed. In the thick wire version, clothes line or other thick wire (#00 to #10) is needed. In that case, it might be possible to erect the antenna without any support other than the boom that holds all four elements.

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