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:

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

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.

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 Yagi antenna. Remember, I've built only three such antennas. Some sacrifices were made in the interest of cost and simplicity. Don't hesitate to experiment 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'll most 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:

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

 

The Design Software
The design software

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

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

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 or 1850-1990 MHz (again, with gaps in the middles). I did not provide a datasheet for the 1850-1990 MHz range because the dimensions of the resulting antenna are much smaller. It's certainly possible to create a Yagi for this range; just use the software to create your own datasheet and 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 the design frequency, but drops more slowly for frequencies below the design frequency. Thus, if your elements' lengths are a bit off during construction, you should still have a usable antenna. Although I have not tried it, you might want to experiment with a design frequency somewhere 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 contact tends to shift the antenna's sensitivity to a higher frequency range, the Yagi Calculator software has compensated for this effect by slightly lengthening the elements. The amount of compensation depends on the boom's diameter (and possibly also the elements' diameter). For this reason, 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 to use the software to create your own datasheet. Similarly, if you plan to use a non-metallic boom, or you plan to mount your elements insulated 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) [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, but you'll pay about the same price for a 5 ft length vs. a 10 ft length. 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, just borrow a hacksaw from the Tools section of Lowes/Home Depot and cut it yourself in the store. Or, ask an employee to cut it for 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 solder EMT as long as you sand-off the finish at the intended soldering point. (EMT does not accept solder as readily as copper, so it's still 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's elements (reflector, driven element, and directors).

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

You can buy a galvanized steel tomato cage from your local hardware/garden store for $2-3. This metal is well-suited for outdoor use. Alternatively, 7-8 metal coat hangers will suffice. I purchased an 8-pack from Walgreens for about $2.50 (shown on the 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 that can be soldered. If you can't find coat hangers or a tomato cage, you can use an old grill, thick copper wire (6-12 AWG), welding rods, or some form of metal tubing, perhaps from an old TV antenna. In fact, using larger-diameter metal is supposed to increase the Yagi's bandwidth, which may lead to better results.

The total length of metal that you'll need depends on the number of elements you intend to put on the Yagi. For the 14-element Yagi shown in this tutorial, we need about 9 ft (2.7 m) of metal.

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

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

The driven element is the only element that's physically connected to the coax (and thus to the modem). The driven element needs to be electrically isolated from the boom; all other 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, for example, 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" hose repair coupling are better choices if you plan to mount your antenna outdoors.

Here, I will demonstrate the use of a 1/2" PVC T-fitting as the plastic 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 the balun and pigtail connection for the antenna.

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

  • If you're using 50-Ohm coax such as LMR400, then use RG58 for the antenna's balun/pigtail.

  • If you're using 75-Ohm coax such as RG6, then use RG59 or RG6 for the antenna's balun/pigtail.

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

RG58 is 50-Ohm coax; RG59 and RG6 are 75-Ohm coax. 50-Ohm coax is theoretically matched to the impedance of the antenna and the modem. But, in practice, the impedance of the antenna varies within the 4G LTE and 3G frequency ranges, so there's no way to be perfectly impedance-matched across the entire band of interest.

The antenna's balun/pigtail is very easy to construct. There's no harm in trying RG59 or RG6 if you already have some on hand. You can always replace it later with the RG58 version. (Click here for more notes on this topic.)

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

 

Building the Yagi

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

 
The following tools and supplies are needed to construct the antenna:
  • Hammer
  • Drill with 3/32" bit (or anything large enough to accommodate the elements)
  • Hacksaw
  • Metal file and coarse sandpaper
  • Center punch (or nail punch, or awl, or strong nail/screw)
  • Wire strippers
  • 4-ft or longer straight edge (ruler or level or other)
  • Ruler with cm scale and mm tick marks
  • Soldering iron (40-80 W preferred); plus solder and flux
  • Permanent 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-ft sections. You'll only need one of the halves, so set the other half aside for another project.

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

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

Again, one of the 5-ft sections of conduit will serve as the antenna'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 the boom, one line on the top, and one line on the bottom. These lines will serve as guides to help ensure that the elements are aligned (see Figure 2).

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

To determine the location of the bottom line, use your ruler to measure 18 mm down from the top line (the diameter of 1/2" EMT conduit is 18 mm). Mark this location. Then, flip the boom over and use the straight edge and marker to draw the bottom line--starting at your mark--in the same fashion used for the top line.


Figure 2: Draw top and bottom guidelines along the length of the boom.
   
Step 3: Mark the positions of the elements
The next step is to mark the position of each element on the boom.

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

Note: The idea is to have marks...
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Figure 3 shows a screenshot of the datasheet for 4G LTE with the element positions highlighted in yellow.

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

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

Note: Unless you happen to have a metric ruler...
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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 four elements based on the 4G LTE Yagi datasheet.


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

   
Step 4: Drill the holes for the reflector and directors
The next step is to drill holes through the boom for the reflector and directors. (No hole is needed for the driven element because it won't be mounted through the boom).

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

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

As you drill the opposite-side hole for each element, run the drill bit briefly though both holes to remove metal shards (Figure 7, right). If your drill bit is too small, you can rock the bit in a circular motion to slightly enlarge the hole (but, don't overdo it--remember, you want a tight fit so that the elements 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
The next step is to measure and cut the reflector and directors according to the Yagi Calculator datasheet.

Figure 8 shows a screenshot of the datasheet for 4G LTE with the 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 the length of each director (again, you can round these to the nearest millimeter).

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

Use a pair of metal-cutting dikes or a hacksaw to cut your elements. You can remove bends by gently pounding them out with a hammer.

Be sure to cut each element a bit long, and then file the element down to the correct length. This filing also helps remove 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 Director 1, which has a length of 178 mm. Figure 10 shows the reflector 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 the boom diameter (9 mm for 1/2" EMT) away from both sides of the midpoint; see Figure 11. These marks will later serve as guides when mounting the elements to the boom. The particular element shown in Figure 11 is the reflector, which has a length of 198 mm, a mark at the midpoint of 99 mm, and flanking marks at 90 mm and 108 mm.

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


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


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 used as the driven element.

The driven element is arguably the most crucial piece of the entire antenna. It's the only element that's directly connected to the coax feed; all other elements serve to focus the signal onto the driven element. The driven element's length will affect the antenna's frequency tuning, and its shape and placement will affect the antenna's impedance.

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

For the 3G version of the antenna, the lengths will be shorter because the design frequency is higher--refer to the actual datasheet PDF.

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

Note: Unless you have specialized bending tools...
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Figure 14 shows the resulting folded dipole, which I created by bending the coat hanger around the spindle of my vise. It's not perfect shape-wise, but it's extremely close to 183 mm length-wise. Also, note that I used a brass-looking coat hanger for this folded dipole only because I already had a spare cut to a total length of 410 mm. You can use the same metal as used for the other elements.

Note: The bend diameter and gap...
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Figure 12: Screenshot of 4G LTE Yagi datasheet with most important folded 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
Now that all of the elements have been created, the next step is to mount only the directors to the boom. (The reflector and driven element will be mounted later.)

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

Now, for each director:

  1. Place the element through its hole in the boom.
  2. Ensure that the element is centered by using the 9-mm-away-from-midpoint marks drawn previously in Step 5 (see Figure 16). You can also measure the amount by which the element protrudes from each side of the boom. It's centered when these protrusion amounts are equal.
  3. Apply a generous amount of flux around the joints.
  4. Solder the element to the boom. To do this, first touch the iron to the joint, wait several seconds for the joint to heat-up, and then feed the solder onto the joint.
Warning: The elements will get hot...
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Figure 17 shows a close-up of one of the solder joints. My soldering job in Figure 17 is poor. There is way more solder than is needed. However, I had a weak 25 W soldering iron that would not stay hot for more than a few seconds after contact with the boom/elements. I had to let the iron reheat for 15-30 seconds after each application, and thus the messy soldering job. It helps to have a more powerful iron or a propane torch.

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


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


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


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


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. This means no metal-to-metal contact and a vertical separation of at least half a boom diameter away from the boom (as a rule of thumb). Thus, to mount the folded dipole, we need some form of insulated standoff.

Figure 19 illustrates how the folded dipole will be positioned around the boom. Because our folded-dipole's bend diameter is 37 mm, and because the boom diameter is 18 mm, the required standoff height is 9.5 mm. A slight deviation from this height is OK (e.g., 10-11 mm instead of 9.5 mm); it will simply result in the folded dipole not being perfectly centered. I have done this in the past with no measurable effect on performance.

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

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

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

  3. Slide the folded dipole through the drilled hole as shown in Figure 21 (you may need to temporarily unfold the dipole to get it around the curves).

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

  5. Bend the folded dipole as needed to be as straight as possible, and then apply epoxy to the hole through which the folded dipole goes through the fitting (see Figure 22).

As you can imagine, there are numerous way to secure the folded dipole to the boom in an insulated fashion. Experiment on your own to determine the technique that you find best, given the parts that you have available.

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

 


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


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


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


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, mount and solder the reflector to the boom. Figure 23 shows the result. (Again, the soldering job is not great.)

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

Note: The only reason the reflector...
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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 coax pigtail to the antenna.

The Yagi Calculator software creates a picture of the balun and pigtail, which is shown in Figure 24 for RG59 coax with polyethylene insulation. Here, I will demonstrate using RG59 because I had a remnant piece with a pre-attached F-type connector.

Note: You can choose the coax type...
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To construct the balun and coax pigtail, first cut and strip the pieces as shown in Figure 25. The top piece will be used to create the balun, and the lower piece will be used for the pigtail.

Note: The length of the balun's loop...
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Next, as shown in Figure 26, simply solder the connections to match Figure 24's diagram. If you're using RG6, you won't be able to solder the outer braid because it's most likely made of aluminum. In this case, just twist the outer braids together and secure them with a crimp fitting.

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

The construction of the antenna is now complete! Figure 28 shows a photo of the completed antenna.


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


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've tested the antenna only in my attic. However, I have tested a 10-element version of this antenna made with a PVC boom, and it yielded impressive 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:

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

  • Software: Verizon Access Manager version 2.6.3.4. This older version of VZAM was used because, unlike the later versions, it displays the RSSI and SINR without going to the diagnostic screen. However, this older version seems to display fewer bars for the same RSSI and SINR as compared to the newer versions.

  • Location: Mid-level in my attic of a one-story home in Stillwater, OK. I would estimate that my attic is about 15 ft above 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 VZW coverage maps. But, I'm within a mile of a regular 4G zone. The LTE 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 same direction.

 
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 of VZAM 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/diversity port. 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 MIMO port, the modem should theoretically use the internal and external antennas in a MIMO configuration. However, this will work only if your internal antenna has a decent signal to begin with. In my setting, as you can see from the above results with no antenna, the signal was 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 UL speeds.

With that in mind, I have experienced even better results with using two of these DIY antennas in a MIMO configuration (i.e., using both ports 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 mounting hardware. The topic of mounting this antenna could benefit from its own DIY article. In regards to cables and coax connectors, there are many 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 points away from the midpoint.

  • One of the advantages of using EMT conduit for the boom is that you can readily find many clamps, elbows, and connectors designed specifically for EMT at your local hardware store; and, they're cheap. Muffler clamps are also cheap or can possibly be salvaged 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't already 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 get started.

  • 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 same time, 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 be an impedance mismatch. However, in my experience with both the UML290 and VL600 modems, the difference in performance is inconsequential (I have not tested other modems). I've tried both RG6 and LMR400 at 50 ft lengths, and I've come to the conclusion that there's more fluctuation due to weather or tower traffic than there is due to the slight impedance mismatch. LMR400 has a bit lower 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 run of 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 loss than 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-type male connectors, search online for a BNC-female to N-female adapter. These are readily available online for around $7 with shipping. 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 your particular modem. There's no easy way to avoid this purchase. Both 3Gstore.com and Verizon Wireless sell these adapter cables for around $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 an FME-female-to-? adapter, where ? depends on your long run of coax.

  • 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 an FME-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 use an F-type barrel connector to change the gender. Of course, you can get creative and use intermediate adapters; below is what I used 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 is based, and thanks to John Drew (VK5DJ) for the Yagi Calculator software. I am also grateful to the following resources for providing much guidance on antennas and related mobile-broadband topics:

 

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Copyright 2012, Damon Chandler and EnCoded Communications Group