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DIY 4G LTE Yagi Antenna in 10 Steps for $10 Datasheet | Parts | Steps | Testing | Notes DIY 4G LTE Yagi Antenna in 10 Steps for $10 by Damon Chandler Copyright © 2012, Damon Chandler and EnCoded Communications Group Last Updated: September 1, 2012 Introduction This article demonstrates how to build a 14-element Yagi antenna for Verizon 4G LTE (or for 3G) in 10 steps for $10. Background Many users in smaller towns and rural locations rely on cellular service as their only source of broadband internet. Unfortunately, being in a rural location often also means being quite far from the nearest cell tower and/or in a weaker signal area due to terrain, trees, or other obstructions. In these situations, an external antenna designed specifically for your cell carrier's frequencies can often make the difference between having a slow and unreliable connection and having a consistently fast connection. The Yagi-Uda antenna--often just called a "Yagi"--is a popular antenna due to its gain, directionality, and relatively lightweight design (see the figure to the right). Unlike the compact internal antenna on a USB modem or cell phone, a Yagi's driven element is large enough to be fully sensitive to the frequencies of interest. But, unlike an omnidirectional antenna or rabbit ears, a Yagi's passive elements can "focus" the signal from a particular direction and reject signals from other directions, thus increasing its directional gain. Yet, unlike other directional antennas (e.g., a parabolic grid), a Yagi usually weighs less than a few pounds. There are many online resources that describe how to create homemade Yagis for VHF, UHF, and WiFi, and for Australia's 3G/NextG networks (see the Acknowledgements section). A particularly useful article by Jim Klitzing ( W6PQL), published in 2006 in the QST journal, provides very detailed instructions on how to build a UHF Yagi antenna. Inspired by these references, I decided to build my own Yagi antenna for the Verizon 4G LTE bands. This tutorial Here, I document the process required to build a 4G LTE Yagi antenna using the construction techniques described in W6PQL's article. His techniques are simple and achievable with relatively common hand tools. I have actually built three antennas based on his techniques, the first two using a PVC boom, and the latest--the one described here (and pictured at the top of this page)--using a metal boom. This tutorial is essentially a spinoff of W6PQL's article for 4G LTE rather than for general UHF. My primary goals were twofold: Keep costs at a bare minimum while still yielding an effective and relatively rugged antenna. 1. Utilize parts that are readily available (e.g., from a local hardware or electronics store). 2. The result came to approximately $10 in parts, 10 steps to construct, and an afternoon of your time (approximately 4-5 hours). This is not bad at all considering that the antenna has a theoretical gain of 13.5 dBd and 15.7 dBi. The same construction techniques can be used to create a 3G antenna; I've provided datasheets for both 4G LTE and 3G versions. DIY LTE Yagi http://bcbj.org/antennae/lte_yagi_diy.htm#parts 1 of 18 28/07/2015 9:46

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DIY 4G LTE Yagi Antenna in 10 Steps for $10 Datasheet | Parts | Steps | Testing | Notes

DIY 4G LTE Yagi Antenna in 10 Steps for $10 by Damon Chandler

Copyright © 2012, Damon Chandler andEnCoded Communications Group

Last Updated: September 1, 2012

Introduction

This article demonstrates how to build a 14-element Yagi antenna for Verizon 4G LTE (or for 3G) in 10 steps for $10.

Background

Many users in smaller towns and rural locations rely on cellular service as their only source of broadband internet. Unfortunately, being in arural location often also means being quite far from the nearest cell tower and/or in a weaker signal area due to terrain, trees, or otherobstructions. In these situations, an external antenna designed specifically for your cell carrier's frequencies can often make the differencebetween having a slow and unreliable connection and having a consistently fast connection.

The Yagi-Uda antenna--often just called a "Yagi"--is a popularantenna due to its gain, directionality, and relativelylightweight design (see the figure to the right). Unlike thecompact internal antenna on a USB modem or cell phone, aYagi's driven element is large enough to be fully sensitive tothe frequencies of interest. But, unlike an omnidirectionalantenna or rabbit ears, a Yagi's passive elements can "focus"the signal from a particular direction and reject signals fromother directions, thus increasing its directional gain. Yet,unlike other directional antennas (e.g., a parabolic grid), aYagi usually weighs less than a few pounds.

There are many online resources that describe how to createhomemade Yagis for VHF, UHF, and WiFi, and for Australia's 3G/NextG networks (see the Acknowledgements section). A particularly usefularticle by Jim Klitzing (W6PQL), published in 2006 in the QST journal, provides very detailed instructions on how to build a UHF Yagiantenna. Inspired by these references, I decided to build my own Yagi antenna for the Verizon 4G LTE bands.

This tutorial

Here, I document the process required to build a 4G LTE Yagi antenna using the construction techniques described in W6PQL's article. Histechniques are simple and achievable with relatively common hand tools. I have actually built three antennas based on his techniques, thefirst two using a PVC boom, and the latest--the one described here (and pictured at the top of this page)--using a metal boom. This tutorialis essentially a spinoff of W6PQL's article for 4G LTE rather than for general UHF. My primary goals were twofold:

Keep costs at a bare minimum while still yielding an effective and relatively rugged antenna.1.Utilize parts that are readily available (e.g., from a local hardware or electronics store).2.

The result came to approximately $10 in parts, 10 steps to construct, and an afternoon of your time (approximately 4-5 hours). This is notbad at all considering that the antenna has a theoretical gain of 13.5 dBd and 15.7 dBi. The same construction techniques can be used tocreate a 3G antenna; I've provided datasheets for both 4G LTE and 3G versions.

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It's important to note that the information provided here is not meant to serve as a definitive reference on how to build an optimal Yagiantenna. Remember, I've built only three such antennas. Some sacrifices were made in the interest of cost and simplicity. Don't hesitate toexperiment with alternative parts or construction techniques based on your own judgment--it's certainly possible to improve the design(e.g., by using larger-diameter elements), and I welcome feedback on such improvements. Note that if you use different materials, you'llmost likely need to generate a different datasheet; see the section on The Design Software.

Organization of this tutorial

The remainder of this article is organized into the following sections:

The Design Software (the software used to design the antenna)1.Parts for the Antenna (the required parts)2.Building the Yagi (the construction steps)3.Quick Testing of the Yagi (preliminary testing results)4.Notes on Mounting, Cables, and Coax Connectors (brief tips on mounting and connecting the antenna)5.Acknowledgements (and links to useful sites)6.User Comments (provide feedback here)7.

The Design Software

The design software

As described in W6PQL's article, I used VK5DJ's Yagi Calculatorsoftware to design the Yagi. The software provides a datasheet withthe required element lengths and positions, and further specs for thecoax connection (balun).

If you plan to follow this tutorial as-is, using the same partsdescribed here, click the link below to download my datasheet foreither 4G LTE or 3G (coax balun info included):

Datasheet for Verizon 4G LTE antenna(787 MHz design frequency; 18 mm metal boom, 2.1 mmelement diameter, elements through boom)

Datasheet for Verizon 3G antenna(894 MHz design frequency; 18 mm metal boom, 2.1 mmelement diameter, elements through boom)

For 4G LTE, Verizon currently uses 747-787 MHz (with a 20 Mhz gap in the middle of this range). For 3G, Verizon uses either 824-894 MHz or1850-1990 MHz (again, with gaps in the middles). I did not provide a datasheet for the 1850-1990 MHz range because the dimensions of theresulting antenna are much smaller. It's certainly possible to create a Yagi for this range; just use the software to create your own datasheetand keep in mind that the boom length can decrease from 5 ft to approximately 2 ft.

The design frequency

Both of the above datasheets have been designed for the top ends of their respective frequency ranges--787 MHz for 4G LTE, 894 MHz for 3G.I chose the maximum frequency as the design frequency because a Yagi's sensitivity supposedly drops very rapidly for frequencies above thedesign frequency, but drops more slowly for frequencies below the design frequency. Thus, if your elements' lengths are a bit off duringconstruction, you should still have a usable antenna. Although I have not tried it, you might want to experiment with a design frequencysomewhere in the middle of each of the above ranges to achieve better performance (e.g., using 767 MHz for 4G LTE).

If you need to make a change

The above datasheets assume that the passive elements make metal-to-metal contact with the boom. Because such metal-to-metal contacttends to shift the antenna's sensitivity to a higher frequency range, the Yagi Calculator software has compensated for this effect by slightlylengthening the elements. The amount of compensation depends on the boom's diameter (and possibly also the elements' diameter). For thisreason, the above datasheets are specific to the parts described here.

If you plan to use a different design frequency, a boom with a different diameter, or elements with a different diameter, then you'll need touse the software to create your own datasheet. Similarly, if you plan to use a non-metallic boom, or you plan to mount your elementsinsulated from the boom, then you'll also need to use the software to create your own datasheet. The software is free and very easy to use(click the image above to download it).

Parts for the Antenna (Total Parts Cost = $10 USD)

Four parts are needed for the antenna:

1/2" x 10 ft Electrical Metallic Tube (EMT) Conduit (approx. $2)

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Rigid Metal Rods (approx. $2-3)Plastic Standoff (approx. $0.50)Short Length of Flexible Coax Cable (approx. $4-5)

1/2" x 10 ft Electrical Metallic Tube (EMT) Conduit (approx. $2) [the link to the left directs to this item at Lowes.com]

We'll use EMT conduit for the antenna's boom.

We need only 5 ft of EMT conduit for a single Yagi antenna, butyou'll pay about the same price for a 5 ft length vs. a 10 ftlength. Plus, you can save the other 5 ft for another Yagi.

Note that if you can't fit the 10-ft EMT into your car, justborrow a hacksaw from the Tools section of Lowes/Home Depotand cut it yourself in the store. Or, ask an employee to cut itfor you.

EMT conduit is a fraction of the cost of aluminum or copper.Similar to aluminum, it's lightweight and more corrosion-resistant than copper. But, unlike aluminum, you can solderEMT as long as you sand-off the finish at the intended solderingpoint. (EMT does not accept solder as readily as copper, so it'sstill a bit of a challenge; be sure to use plenty of flux.)

Rigid metal rods (12 gauge or thicker) (approx. $2-3) [the link to the left directs to a steel tomato cage at Lowes.com]

We'll need some form of thick, rigid metal for the antenna'selements (reflector, driven element, and directors).

There are many options for this metal, spanning a wide range ofprices. Two of the cheapest options that I've found are agalvanized steel tomato cage or metal coat hangers.

You can buy a galvanized steel tomato cage from your localhardware/garden store for $2-3. This metal is well-suited foroutdoor use. Alternatively, 7-8 metal coat hangers will suffice. Ipurchased an 8-pack from Walgreens for about $2.50 (shown onthe right). These particular hangers have a plastic coating,which can easily be stripped off.

Keep in mind that you really just need metal rods or tubes thatcan be soldered. If you can't find coat hangers or a tomatocage, you can use an old grill, thick copper wire (6-12 AWG),welding rods, or some form of metal tubing, perhaps from anold TV antenna. In fact, using larger-diameter metal issupposed to increase the Yagi's bandwidth, which may lead tobetter results.

The total length of metal that you'll need depends on thenumber of elements you intend to put on the Yagi. For the14-element Yagi shown in this tutorial, we need about 9 ft (2.7m) of metal.

Plastic Standoff (approx. $0.50) [the link to the left directs to a PVC T-fitting at Lowes.com]

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We'll need one plastic standoff to mount the Yagi's drivenelement to the EMT conduit (boom).

The driven element is the only element that's physicallyconnected to the coax (and thus to the modem). The drivenelement needs to be electrically isolated from the boom; allother elements will be soldered to the boom.

Find something which you can repurpose for use as the standoff,preferably something durable. A plastic bottle cap, forexample, will work; but, it might not last long in the sun. A 1/2"PVC T-fitting, an electric fence insulator, or even a 1/2" hoserepair coupling are better choices if you plan to mount yourantenna outdoors.

Here, I will demonstrate the use of a 1/2" PVC T-fitting as theplastic standoff.

Short Length of Flexible Coax Cable (approx. $4-5) [the link to the left directs to an RG58 cable at WeConnex.com]

We'll need about 1.5 ft of flexible coax cable to create thebalun and pigtail connection for the antenna.

For this short length of coax, I suggest choosing the type of coaxwith the same impedance as your longer coax run (the long runof coax that connects the modem to the antenna).

If you're using 50-Ohm coax such as LMR400, then useRG58 for the antenna's balun/pigtail.

If you're using 75-Ohm coax such as RG6, then use RG59or RG6 for the antenna's balun/pigtail.

The previously described datasheets contain informationregarding the baluns for RG58, RG59, and RG6.

RG58 is 50-Ohm coax; RG59 and RG6 are 75-Ohm coax. 50-Ohmcoax is theoretically matched to the impedance of the antennaand the modem. But, in practice, the impedance of the antennavaries within the 4G LTE and 3G frequency ranges, so there's noway to be perfectly impedance-matched across the entire bandof interest.

The antenna's balun/pigtail is very easy to construct. There's noharm in trying RG59 or RG6 if you already have some on hand.You can always replace it later with the RG58 version. (Clickhere for more notes on this topic.)

Here, I will demonstrate using RG59 because I had a remnantpiece available (with a pre-attached F-type connector).

Building the Yagi

The following 10 steps will be used to build the antenna:

Making the boomStep 1: Cut the EMT conduit in halfStep 2: Draw guide lines along the length of the boomStep 3: Mark the positions of the elementsStep 4: Drill the holes for the reflector and directors

Making the elementsStep 5: Measure and cut the reflector and directorsStep 6: Measure and cut the driven element

Mounting the elements to the boomStep 7: Mount the directors to the boomStep 8: Mount the folded dipole to the boomStep 9: Mount the reflector to the boom

Making and mounting the coax connection

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Step 10: Create and attach the balun and coax pigtail

The following tools and supplies are needed to construct the antenna:

HammerDrill with 3/32" bit (or anything large enough to accommodate the elements)HacksawMetal file and coarse sandpaperCenter punch (or nail punch, or awl, or strong nail/screw)Wire strippers4-ft or longer straight edge (ruler or level or other)Ruler with cm scale and mm tick marksSoldering iron (40-80 W preferred); plus solder and fluxPermanent markers (one fine-tip marker and one medium-tip marker)Epoxy and screws

If you don't have a particular tool, it's certainly possible to use a substitute. A vise is also highly recommended.

Step 1: Cut the EMT conduit in half

Using a hacksaw, cut the 10-ft EMT conduit into two 5-ftsections. You'll only need one of the halves, so set the otherhalf aside for another project.

It helps to use a vise to hold the conduit while cutting (seeFigure 1). If you don't have a vise, you can use clamps oryour foot.

After you've cut the conduit, briefly sand or file the cut endsto remove any of shards of metal.

Again, one of the 5-ft sections of conduit will serve as theantenna's boom.

Figure 1: Cut the 10-ft EMT conduit into two 5-ft sections.

Step 2: Draw guide lines along the length of the boom

The next step is to draw two lines along the length of theboom, one line on the top, and one line on the bottom.These lines will serve as guides to help ensure that theelements are aligned (see Figure 2).

To draw the top line, place your straight edge along thelength of the boom, clamp the boom to the straight edge (orstep on the boom to prevent movement), and then follow thestraight edge with your marker, drawing a line on the boom.

To determine the location of the bottom line, use your rulerto measure 18 mm down from the top line (the diameter of1/2" EMT conduit is 18 mm). Mark this location. Then, flip theboom over and use the straight edge and marker to draw thebottom line--starting at your mark--in the same fashion usedfor the top line.

Figure 2: Draw top and bottom guidelines along the length of the boom.

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Note: The idea is to have marks...

Note: Unless you happen to have a metric ruler...

Step 3: Mark the positions of the elements

The next step is to mark the position of each element onthe boom.

Using your ruler and marker, measure along one of the guidelines and mark the positions of the elements according to theYagi Calculator datasheet. Repeat this process for the otherguide line. Thus, you should have marks for the elements onboth sides of the boom (i.e., along both guide lines).

Figure 3 shows a screenshot of the datasheet for 4G LTE withthe element positions highlighted in yellow.

The reflector is to be located 30 mm from thebeginning of the boom.The radiator (driven element) is to be spaced 76 mmfrom the reflector, which is 106 mm from thebeginning of the boom.For the directors, the "Spaced" column indicates thespacing from the previous element. The "Boomposition" column indicates the position relative to thebeginning of the boom.

Figure 4 shows an illustration of the relative position("Spaced") and absolute positions ("Boom position") of thefirst four elements.

Figure 5 shows the boom with the marked positions. The "FD"stands for "folded dipole;" this is the driven element(radiator).

Figure 3: Screenshot of 4G LTE Yagi datasheet with positions highlighted.

Figure 4: Diagram of the relative and absolute positions of the first fourelements based on the 4G LTE Yagi datasheet.

Figure 5: Mark the position of each element along the guide lines on bothsides of the boom.

Step 4: Drill the holes for the reflector and directors

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The next step is to drill holes through the boom for thereflector and directors. (No hole is needed for the drivenelement because it won't be mounted through the boom).

To keep the drill-bit from drifting during drilling, use acenter punch to make an indentation at each markedposition (except for the driven element); see Figure 6. If youdon't have a center punch, a nail punch, awl, or even astrong nail or screw will work. (As you can see in thebackground of the left image of Figure 7, I had an actual nailpunch, but I couldn't find it when I needed it; so I resorted tousing a plain nail.)

Next, drill the holes halfway through from each side of theboom (see Figure 7, left). If you don't have a drill bit thatmatches the size of your elements, it's better to go slightlysmaller, since you want a tight fit during soldering.

As you drill the opposite-side hole for each element, run thedrill bit briefly though both holes to remove metal shards(Figure 7, right). If your drill bit is too small, you can rockthe bit in a circular motion to slightly enlarge the hole (but,don't overdo it--remember, you want a tight fit so that theelements don't move during soldering).

Figure 6: Make an indentation at each marked position.

Figure 7: Drill the holes halfway through from each side of the boom.

Step 5: Measure and cut the reflector and directors

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Note: It's wise to label the elements...

The next step is to measure and cut the reflector anddirectors according to the Yagi Calculator datasheet.

Figure 8 shows a screenshot of the datasheet for 4G LTE withthe reflector and director lengths highlighted in yellow.

The reflector is 197.6 mm long (round to 198 mm).For the directors, the "Length" column indicates thelength of each director (again, you can round these tothe nearest millimeter).

The datasheet states that the elements lengths must bewithin one millimeter of the stated lengths.

Use a pair of metal-cutting dikes or a hacksaw to cut yourelements. You can remove bends by gently pounding themout with a hammer.

Be sure to cut each element a bit long, and then file theelement down to the correct length. This filing also helpsremove jagged edges from the cut ends.

Figure 9 shows one of the elements, stripped, straightened,and then cut/filed to length. The element shown is Director1, which has a length of 178 mm. Figure 10 shows thereflector and all 12 directors cut to length.

After all of the elements are cut to the proper lengths,mark the midpoint of each element. Also mark half theboom diameter (9 mm for 1/2" EMT) away from both sides ofthe midpoint; see Figure 11. These marks will later serve asguides when mounting the elements to the boom. Theparticular element shown in Figure 11 is the reflector, whichhas a length of 198 mm, a mark at the midpoint of 99 mm,and flanking marks at 90 mm and 108 mm.

Figure 8: Screenshot of 4G LTE Yagi datasheet with lengths highlighted.

Figure 9: Cut each element a bit long, and then file it down to the correctlength.

Figure 10: All 12 elements cut to length and organized.

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Note: Unless you have specialized bending tools...

Note: The bend diameter and gap...

Figure 11: Mark the midpoint and two 9-mm-away-from-midpoint points.

Step 6: Measure and cut the driven element

Now it's time to tackle the folded dipole that will be usedas the driven element.

The driven element is arguably the most crucial piece of theentire antenna. It's the only element that's directlyconnected to the coax feed; all other elements serve tofocus the signal onto the driven element. The drivenelement's length will affect the antenna's frequency tuning,and its shape and placement will affect the antenna'simpedance.

The Yagi Calculator datasheet lists the specs of the foldeddipole, a screenshot of which is shown in Figure 12 (for 4GLTE) with the most important parts highlighted. As stated inthe datasheet, the distances should be measured from theinsides of the bends (inner edge on one side to inner edge onthe other side).

For the 3G version of the antenna, the lengths will be shorterbecause the design frequency is higher--refer to the actualdatasheet PDF.

To create the folded dipole, cut a length of your metalslightly longer than the datasheet's "Total rod length" (403mm). Then, mark the distances HI and GF (70 mm). Next,bend the coat hanger around some round object to createthe bends (e.g., a can, bottle, jar, etc.). Figure 13 illustratesthe basic structure for which you should aim.

Figure 14 shows the resulting folded dipole, which I createdby bending the coat hanger around the spindle of my vise. It'snot perfect shape-wise, but it's extremely close to 183 mmlength-wise. Also, note that I used a brass-looking coathanger for this folded dipole only because I already had aspare cut to a total length of 410 mm. You can use the samemetal as used for the other elements.

Figure 12: Screenshot of 4G LTE Yagi datasheet with most importantfolded dipole dimensions highlighted.

Figure 13: Illustration of folded dipole shape and important dimensions.

Figure 14: Actual folded dipole created from a coat hanger.

Step 7: Mount the directors to the boom

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Warning: The elements will get hot...

Now that all of the elements have been created, the nextstep is to mount only the directors to the boom. (Thereflector and driven element will be mounted later.)

Because we'll be soldering the directors to the boom, weneed to prep the surfaces to ensure that they accept thesolder. To do this, sand around each hole on the boom (seeFigure 15).

Now, for each director:

Place the element through its hole in the boom.1.Ensure that the element is centered by using the9-mm-away-from-midpoint marks drawn previously inStep 5 (see Figure 16). You can also measure theamount by which the element protrudes from eachside of the boom. It's centered when these protrusionamounts are equal.

2.

Apply a generous amount of flux around the joints.3.Solder the element to the boom. To do this, first touchthe iron to the joint, wait several seconds for the jointto heat-up, and then feed the solder onto the joint.

4.

Figure 17 shows a close-up of one of the solder joints. Mysoldering job in Figure 17 is poor. There is way more solderthan is needed. However, I had a weak 25 W soldering ironthat would not stay hot for more than a few seconds aftercontact with the boom/elements. I had to let the iron reheatfor 15-30 seconds after each application, and thus the messysoldering job. It helps to have a more powerful iron or apropane torch.

After you've soldered all of the directors, sight down theboom to check that the directors are aligned (see Figure 18).Bend the directors as needed to correct for inevitablemisalignments.

Figure 15: Sand around each hole down to the bare metal to ensure thatthe solder will bond.

Figure 16: Place each element through its hole, and ensure that it'scentered across the boom by using the 9-mm-away-from-midpoint marksdrawn previously in Step 5.

Figure 17: Closeup of solder joints (they're not perfect, but they're quitesolid).

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Figure 18: Sight down the boom to ensure alignment of the elements;bend the elements as needed to correct.

Step 8: Mount the folded dipole to the boom

The next step is to mount the folded dipole to the boom.

The folded dipole needs to be insulated from the boom. Thismeans no metal-to-metal contact and a vertical separationof at least half a boom diameter away from the boom (as arule of thumb). Thus, to mount the folded dipole, we needsome form of insulated standoff.

Figure 19 illustrates how the folded dipole will be positionedaround the boom. Because our folded-dipole's bend diameteris 37 mm, and because the boom diameter is 18 mm, therequired standoff height is 9.5 mm. A slight deviation fromthis height is OK (e.g., 10-11 mm instead of 9.5 mm); it willsimply result in the folded dipole not being perfectlycentered. I have done this in the past with no measurableeffect on performance.

To use the PVC T-fitting as the standoff, do the following:

Slide the T-fitting onto the boom, measure 9.5 mm upfrom the top of the boom, and then mark and drill ahole from each side (see Figure 20).

1.

Trim the ends of the "T" so that the fitting can slideinto place without hitting the first driven element.(You really only need to trim one end of the "T"--theend that will face toward the first director.)

2.

Slide the folded dipole through the drilled hole asshown in Figure 21 (you may need to temporarilyunfold the dipole to get it around the curves).

3.

Drill two holes for mounting screws, and then mountthe fitting + folded dipole onto the boom using thesetwo screws (see Figure 22). Ensure that the foldeddipole lines up with your previous position mark forthe driven element (you may need to rotate theT-fitting to see this mark).

4.

Bend the folded dipole as needed to be as straight aspossible, and then apply epoxy to the hole throughwhich the folded dipole goes through the fitting (seeFigure 22).

5.

As you can imagine, there are numerous way to secure the

Figure 19: Illustration of the general idea behind using a plastic standoff.

Figure 20: Prepare the PVC T-fitting by trimming the ends and drillingtwo opposite-side holes through which the folded dipole will fit.

Figure 21: Slip the folded dipole through the holes (you might need toundo some bends temporarily).

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Note: The only reason the reflector...

Note: You can choose the coax type...

folded dipole to the boom in an insulated fashion.Experiment on your own to determine the technique that youfind best, given the parts that you have available.

A better alternative to the T-fitting would be to use someform of plastic box such as a plastic conduit body. This way,you can potentially enclose your coax connections inside thebox.

Figure 22: Attach the assembly to the boom.

Step 9: Mount the reflector to the boom

The next step is to mount the reflector to the boom.

Following the same procedure described in Step 7, mountand solder the reflector to the boom. Figure 23 shows theresult. (Again, the soldering job is not great.)

After mounting the reflector, sight down the boom to ensureit's aligned with the directors, and bend as needed tomaximize alignment.

Figure 23: Solder the reflector to the boom.

Step 10: Create and attach the balun and coax connection

The final step is to create and attach the balun and coaxpigtail to the antenna.

The Yagi Calculator software creates a picture of the balunand pigtail, which is shown in Figure 24 for RG59 coax withpolyethylene insulation. Here, I will demonstrate using RG59because I had a remnant piece with a pre-attached F-typeconnector.

To construct the balun and coax pigtail, first cut and stripthe pieces as shown in Figure 25. The top piece will be usedto create the balun, and the lower piece will be used for thepigtail.

Figure 24: Diagram of balun and coax pigtail for 4G LTE Yagi withpolyethylene-insulated RG59.

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Note: The length of the balun's loop...

Next, as shown in Figure 26, simply solder the connections tomatch Figure 24's diagram. If you're using RG6, you won't beable to solder the outer braid because it's most likely madeof aluminum. In this case, just twist the outer braidstogether and secure them with a crimp fitting.

Finally, as shown in Figure 27, solder the center conductorsof the balun to the folded dipole and use tie-wraps to securethe coax. If you plan to mount the antenna outdoors, be sureto cover the stripped portions of the coax with a thickcoating of epoxy to prevent water ingress.

The construction of the antenna is now complete! Figure28 shows a photo of the completed antenna.

Figure 25: Cut and strip the pieces for the balun (top) and coax pigtail(bottom).

Figure 26: Solder the connections to match the diagram.

Figure 27: Attach the balun and pigtail to the folded dipole.

Figure 28: Completed antenna.

Quick Testing of the Yagi

Due to weather constraints (and an intimidating nest of hornets), I have not yet had a chance to test this particular antenna on my roof; I'vetested the antenna only in my attic. However, I have tested a 10-element version of this antenna made with a PVC boom, and it yieldedimpressive speed boosts placed on a mast on my roof. I plan to provide more thorough test results in the near future.

For now, here are some quick test results of the antenna in my attic,on a tripod, and using the UML290 modem.

Some brief details of the testing:

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Modem: Pantech UML290 connected directly to laptop (.230firmware). The antenna was plugged into the modem's normalantenna port, and not the MIMO/diversity port.

Software: Verizon Access Manager version 2.6.3.4. This olderversion of VZAM was used because, unlike the later versions, itdisplays the RSSI and SINR without going to the diagnosticscreen. However, this older version seems to display fewer barsfor the same RSSI and SINR as compared to the newer versions.

Location: Mid-level in my attic of a one-story home inStillwater, OK. I would estimate that my attic is about 15 ftabove the ground, and the tripod adds another 4 ft.

Terrain: In a shallow valley. Many trees around, with leaves,but the trees are short (20-40 ft is my guess).

Coverage: I'm in an Extended 4G zone according to VZWcoverage maps. But, I'm within a mile of a regular 4G zone. TheLTE tower is 7-8 miles away.

Aiming: I knew the general direction in which to aim based on my other antenna adventures. I pointed this antenna in that samedirection.

Results with no external antenna

RSSI: -90 to -86 dBm.SINR: -3 to 2 dB.Speeds: 2-5 Mbps DL, less than 0.3 Mbps UL.

Results with the DIY antenna

RSSI: -77 to -72 dBm.SINR: 12 to 17 dB.Speeds: 15-23 Mbps DL, 5-8 Mbps UL.

The results are promising. I expect further performance gains by mounting the antenna higher and outdoors. Again, this older version ofVZAM seems to display fewer bars for the same RSSI and SINR as compared to the newer versions. I always run a speed test to be sure.

During these tests, the antenna was plugged into the modem's normal antenna port (the one near the SIM card), and not the MIMO/diversityport. 3Gstore.com calls the normal antenna port the "3G port" and the MIMO/diversity port the "4G port." If you plug the antenna into the

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MIMO port, the modem should theoretically use the internal and external antennas in a MIMO configuration. However, this will work only ifyour internal antenna has a decent signal to begin with. In my setting, as you can see from the above results with no antenna, the signalwas quite poor to begin with, so plugging the antenna into the MIMO port gave me about the same DL speeds, but it didn't help the ULspeeds.

With that in mind, I have experienced even better results with using two of these DIY antennas in a MIMO configuration (i.e., using bothports of the VL600 or UML290). I hope to post some MIMO results in the near future.

Notes on Mounting, Cables, and Coax Connectors

There are always hidden costs to every DIY project, and this project is no exception. Here, the culprit is connectors, cables, and mountinghardware. The topic of mounting this antenna could benefit from its own DIY article. In regards to cables and coax connectors, there aremany good online resources for this topic. Here, I provide some brief notes on these topics.

Notes on mounting

At the present, I have not yet explored ideal mounting options. This topic deserves its own DIY article.

Although EMT conduit is a fairly lightweight, I recommend supporting the antenna from its midpoint or at two equidistant pointsaway from the midpoint.

One of the advantages of using EMT conduit for the boom is that you can readily find many clamps, elbows, and connectorsdesigned specifically for EMT at your local hardware store; and, they're cheap. Muffler clamps are also cheap or can possibly besalvaged locally. You'll have to experiment and be creative if you plan to pursue DIY mounting hardware.

Of course, the quickest and easiest solution is to purchase an antenna mounting kit, e.g., from your local RadioShack. If you don'talready have a mast or other mount on your roof (e.g., for a TV antenna), then you'll need some form of mounting kit to getstarted.

If you don't have a metal roof, consider mounting the antenna in your attic. You won't get the best signal possible, but at the sametime, you won't have to worry about rust, lightening, or wind.

Notes on the long run of coax

If you have RG6 already in your walls, or you have a long run of spare RG6 available, then by all means, use it. Yes, there will bean impedance mismatch. However, in my experience with both the UML290 and VL600 modems, the difference in performance isinconsequential (I have not tested other modems). I've tried both RG6 and LMR400 at 50 ft lengths, and I've come to the conclusionthat there's more fluctuation due to weather or tower traffic than there is due to the slight impedance mismatch. LMR400 has a bitlower loss than RG6 (see here), but the cost and labor needed to run a new length of LMR400 is something to consider.

If you have RG59 already in your walls, then I'd suggest replacing it with either RG6 or LMR400. If you don't already have a long runof spare RG6 available, then go with LMR400. Although I've never tried a long run of RG59, it's reported to have a much greater lossthan the other two types in the LTE frequency range (see here).

If you don't already have cables in your walls, and you don't already have a long run of spare RG6 available, then go with LMR400.If you have to buy cable, and you have to spend the time to fish it through your walls, then you might as well use LMR400.

Notes on connecting the antenna to the long run of coax

How you connect the antenna to your long run of coax depends on what you used for the antenna's pigtail cable.

If you used RG58 for the antenna's pigtail, then it probably has a BNC male connector. Assuming your LMR400 cable uses N-typemale connectors, search online for a BNC-female to N-female adapter. These are readily available online for around $7 withshipping. Or, better yet, buy your RG58 with an N-female connector.

If you used RG59 or RG6 for the antenna's pigtail, then you can easily find an F-type barrel connector at your local Walmart, Lowes,or other store. A 2-pack at Walmart runs for $3.

Notes on connecting the long run of coax to your modem

To attach the other end of the long run of coax to your modem, you will need to purchase a short adapter cable designed for yourparticular modem. There's no easy way to avoid this purchase. Both 3Gstore.com and Verizon Wireless sell these adapter cables foraround $10-15, and both of these places ship quickly. Your local Verizon Wireless shop may also have some in stock.

These short adapter cables almost always have an FME male connector to connect to the long run of coax. You will need to find anFME-female-to-? adapter, where ? depends on your long run of coax.

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If you used LMR400 for your long run of coax, and assuming it uses N-type male connectors, then you will need to search for anFME-female to N-female adapter. These are readily available online for around $10 with shipping.

If you used RG59 or RG6 for the antenna's pigtail, then you will need to search for an FME-female to F-female adapter.Maxmost.com sells an an FME-female to F-male adapter here and on eBay here for around $10 shipped from NY. You can then usean F-type barrel connector to change the gender. Of course, you can get creative and use intermediate adapters; below is what Iused during my tests (I'm actually surprised it works as well as it does).

Acknowledgements

A special thanks to Jim Klitzing (W6PQL) for providing an excellent QST journal article from which much of the material on this page isbased, and thanks to John Drew (VK5DJ) for the Yagi Calculator software. I am also grateful to the following resources for providing muchguidance on antennas and related mobile-broadband topics:

EVDOforums.com and 3Gstore.comVerizon Wireless forums at DSLReports.comJim_in_VA's excellent EVDO Tips siteHomemade 3G/NextG Yagis for all bands site from our friends down underVHF/UHF Yagi Antenna Design site from Martin E. Meserve (K7MEM)Jealous Brothers' blog post on the Wilson 4G LTE amp and antennasMilkwood's blog post on DIY remote area internet

User Comments

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25 Comments Sort by

David Berry · University of self taughtDamon. Prepping to build this for our vacation place in the U.P. Of Michigan using an AT&T UniteHotspot, Freq. B17. Anybody build one for AT&T 4G LTE yet?Like · Reply · Jul 2, 2015 5:41pm

Krystal Mae Suarez · Flight Attendant at Philippine AirlinesHi sir i'm trying to create this with 1800Mhz frequency can you send me a datasheet which include allcalculations,i'm planning the same material to use..thnks in advance.Like · Reply · May 4, 2015 9:49am

Pravin Kumar · Toranagallu, Karnataka, IndiaI made one last week but didn't test it till yesterday. I think I am doing something wrong because therewas signal drop instead of an increase. can you help me out a bitLike · Reply · Apr 15, 2015 11:59pm

Chris Adams · Manager/Personal Trainer at Norton Fitnessi am trying to create one for sprint 4g lte, they run off of 800, 1900,2500MHz can you send me a datasheet or the information used for the data sheet to calculate it? i will be useing the same materailesyou used and i am looking at the 800MHz

Like · Reply · Apr 1, 2015 11:26am

Damon Chandler · Stillwater, OklahomaHi Chris: Do you know the exact frequency range of Sprint's 800 MHz LTE?

Like · Reply · Apr 1, 2015 10:57pm

Chris Adams · Manager/Personal Trainer at Norton FitnessDamon Chandler 814-849 MHzLike · Reply · Apr 3, 2015 3:46pm

Chris Adams · Manager/Personal Trainer at Norton Fitnessi have cage wire and hangers which one would you recommend the cage wire is 3.68 mmdiameterLike · Reply · Apr 3, 2015 3:48pm

Show 2 more replies in this thread

Tou Viravongsa · Works at Dragon DinerHi Damon I just finished building one it was working just fine untill 2 hour later i experirned signal dropand my signal kept disconnecting could you help me find out what went wrong with my antenna thanks

Like · Reply · Feb 16, 2015 9:15am

Damon Chandler · Stillwater, OklahomaHi Tou: Sorry for the late reply. Were you eventually able to resolve this?

Like · Reply · Apr 1, 2015 10:56pm

Damon Barber · Big Bend Community CollegeHi Damon! Im Damon. I work with a Damien, but thats another story.? Building a Yagi antenna forthe SeaHawks game tomorrow. The signal is about 70mi away, so we shall see! Great tutorial, andwonderful relation of the directors to the magnefying lenses. BTW I hear there may be another JasonBourne Movie on the horizon, and original director.Like · Reply · Feb 1, 2015 12:37am

Damon Chandler · Stillwater, OklahomaHi Damon! (Wow, I don't think I've ever typed that before.) Thanks for the feedback. Hopethe build worked out for you. Cheers!

Like · Reply · 1 · Feb 15, 2015 8:16pm

Chad HugginsFinished building one this weekend. Works great! Didn't take any before or after speed data, but canreally tell a difference.

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