Easy-to-Build Homebrew Portable Vertical Antennaby Charles Kight, AI4UN

https://ai4un.wordpress.com/April 3, 2018

In preparation for a “Domestic Field Day Expedition” to Syracuse, NY in 2017, I needed to find an effective antenna to operate from an area about 25 by 25 feet square. In doing my research, I came across the FXTenna (TM) Portable Antenna by Dave Land, KD5FX (http://www.kd5fx.com/FXportable/fx_portable_antenna.htm) that will operate on 20-6 meters. Many thanks to Dave for all of his hard work. Over the last year, I have built andtested 4 different versions based on Dave’s original design focusing on making changes to the base and increasingthe ease of deployment. For those interested, a version history of my first three versions is provided at the end of this document.

The following description and instructions are for my fourthversion. This portable antenna is a normal quarter waveresonant vertical on 20-6 meters and uses sixteen groundmounted radials. Band changes are made by collapsing aspecific number of sections. With an appropriate radial system,this version provides very good performance on 20-6 metersand will also work well on 30 and 40 meters with inverted Lextensions. It will easily handle 100 Watts and probably muchmore. The following are some additional advantages, features,options, and disadvantages:

• Inexpensive◦ less than $150 using new parts

• Easy to Build◦ minimal skills and only simple tools required◦ no soldering required◦ only 3 radio specialty items required◦ good beginner project

• Easy to Use◦ short and relatively stable – less than 18 feet tall◦ since the radiating element is telescoped rather than tilted, it may be used in a group of trees or other

obstructions with a small vertical opening (But Never near overhead wires!)◦ no guying required so it may be used on concrete or asphalt ◦ antenna is lightweight and may be constructed to be easily storable/shippable◦ self supporting V shaped mast stand is integral to the design◦ bright color radials and quick release alligator clips makes setup easier and minimize trip risk

• Extra Cost Options◦ 40 and 30 meter inverted L extensions (if space allows)◦ perimeter barrier for special events◦ carrying case

Disadvantages:• must be readjusted when changing bands• too large and heavy to be easily back-packed• takes about 20-30 minutes to set up – not suitable for very short deployments• ground radials may limit use in public, in heavily traveled areas, or around pets or children• over time, the alligator clips and radial ring may corrode unless protected • inverted L extensions must be used with caution to avoid bending the vertical element• no tuner is generally required, however, a simple built in 3:1 tuner may be needed for some bands, for

some radial lengths, if the antenna is slightly miss-adjusted, or if ground conditions are poor

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DISCLAIMER

This antenna is not a kit; you have to procure the components and build it yourself. It is intended only for temporary portable operation. It may not suit your needs. The information in this document is provided at no cost, “as is”, and with no warranty as to its accuracy or to its appropriateness for your situation. Always follow accepted safety standards. Read this entire document and consider all options and risks before deciding to purchase components or to build this antenna.

Detailed Antenna Description

The base antenna consists of four main parts: whip, mount, PVC mast and triangular base assembly, and radial assembly. Options include an inverted L extension, perimeter barrier, and case.

1. MFJ-1979 stainless steel telescoping whip. This is the vertical radiating part of the antenna. There is currently no substitute for this item. While I am not generally fond of MFJ products due to a poor reputation for both quality control and customer support, this item appears to be an exception. I have purchased 3 of these, and those that I have ordered were of good quality. Eham currently shows 16 reviews with a 4.7 average. The whip is available from a variety of sources, but is frequently out of stock, so check around. I ordered mine from http://www.randl.com/shop/catalog/product_info.php?products_id=68253. When you receive the whip, extend it completely, measure it, and inspect it carefully (it should be 17 feet tip to tip).

While this whip works very well, it is thin and the top will bow slightly if the whip is not perfectly vertical. This will happen in the wind or if the ground is not level. This is not a problem, just an observation. However, if an inverted L extension is used, it will bow considerably, so care must be taken to make sure that it is not over-stressed.

2. Compatible Mobile Mount. I recommend using the Firestik 3-Way CB Mount (Model SS-64A). Whileyou may use substitutions, it is not recommended. The Firestik is an excellent quality stainless steel mount at a very reasonable price. It will fit the preferred 1” PVC pipe and fittings, so if you use another, you might have to change those items.

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I ordered my Firestik 3-Way CB Mount from https://www.rightchannelradios.com/collections/cb-antenna-mounts/products/firestik-3-way-cb-mirror-mount, and I was VERY pleased with both the processand the product. The email communications were timely, informative and even entertaining.

I do not recommend the use of an MFJ mount such as the MFJ-342T. I first purchased and tried an MFJ-342T, and the SO-239 socket was so tight that a short coax patch cable used for testing got stuck and was ruined when removed. This mount will also only allow the use of 1/2” PVC pipe and fittings, so the base for this mount will be weaker if it used. In a month long exposure test, the bolts for the MFJ-342T also showed signs of corrosion. While I ultimately repaired the MFJ mount and am using it in my back-up antenna (it is used in some photos), the Firestik mount is considerably better for this project.

Although the bolts that come with the MFJ mount are long enough to use with 1/2” pipe, the bolts that come with the Firestik are not long enough for any size PVC pipe, so if you use the Firestik you will needto get longer bolts from you local hardware store. I suggest taking the mount with you to make sure that the bolts will attach it to chosen size PVC pipe. Make sure that you get stainless steel bolts, and make sure that the nuts that come with the Firestik will fit the bolts that you purchase.

3. PVC Mast and Triangular Base Assembly. The base assembly is constructed of schedule 40 PVC pipe and fittings. The 1” size is preferred for both strength and weight but requires using the Firestik mount. The MFJ will only accommodate 1/2” pipe and fittings. You will need at least 10 feet of pipe, 3 caps, and a Side Outlet PVC Elbow. You will also need 2 or more couplers if you cut the legs for transport. Velcro strapping with a screw is needed if you use the stress relief strap. The base looks awkward, but is stable and works well since the location of the mount between the legs and the weight of the legs keeps the center of gravity well within the triangular base. While the ground does not have to exactly level, uneven ground should be avoided – mostly level and even ground is preferred.

The assembly consists of the following:

1. An appropriately sized Side Outlet PVC Elbow PVC fitting (available atLowe's and other hardware stores): This is the main part of the assembly.Make sure that you can get this item before committing to the other parts of theantenna since it is sometimes difficult to locate. My local Lowes store had thesein stock. Make sure that all openings are the same size and DO NOT have screwthreads – the mast and legs need to slip into it.

2. A PVC mast with PVC Cap: You will attachthe mount to this part. It needs to be at least longenough to attach the mount and the cap and toinsert the mast into the Side Outlet PVC Elbowbase. If you intend to use an inverted Lextension, I recommend making it 12” long sothat a stress relief strap may be installed near thetop.

My stress relief strap used two-sided hook andloop strapping and was attached to the whip sideof the mast using a screw through one layer ofstrap between the mast and the whip. Afterattaching the whip, the strap was wrapped andadjusted to make the sure that the whip wasvertical. You will probably only ever have to adjust the strap one time. The whip is easy to remove without unfastening the strap. The mast with stress relief strap shown above uses 1” pipe and the Firestick mount.

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3. Mast legs with end caps: These need to be at least 4 feet long (longer for extreme conditions or for smaller size PVC pipe) and may be cut for transport or storage if PVC couplers are used to put them together when deploying the antenna. If you get 10 feet of pipe and cut a 1 foot mast, that will leave 4.5 feet for each leg.

IMPORTANT: No glue is used in the PVC Mast and Triangular Base Assembly. All parts are pressure fit for ease of disassembly for transport and maintenance.

4. Radial Assembly. A 1/4 wavelength vertical antenna’s effectiveness is only as good as its radial system. While a small number of elevated radials (counterpoises) are very effective, they have to be cut for a single band, make the antenna higher, and require additional elevated attachment points. As such, they are not appropriate for this antenna. This antenna uses ground mounted radials. Ground mounted radials can be used for multiple bands but their length and number significantly effect performance. For permanent installations, 32 radials that are at least 0.20 times the wavelength of the lowest frequency to be used is generally considered to be cost and performance effective. For this portable antenna, 16 radials that are at least 0.1 wavelength long is probably the most convenient and cost/performance effective. For 40 meters (using the inverted L extension), 13 feet is a good compromise length. Sixteen 13-foot radials perform about as well as my 130 ft long end-fed antenna that is about 40 feet up at each end. Sixteen 5-foot radials are only about 70% as effective and are the shortest that I recommend due to SWR and RFI/common mode current concerns. Due to space limitations, I use sixteen 8-foot radials for most deployments resulting in performance that is about 80-85% as effective as my 130 ft long end-fed antenna.

The radial assembly for this antenna consists of: a radial ring, sixteen easy-to-deploy radials with alligatorclips to attach to the radial ring, mount connector wires that connect the mount to the radial ring, and a method of holding down the ends of the radials.

1. Radial Ring: While anything that allows the sixteen radials to beelectrically connected together and then to the mount will work, themost effective and inexpensive thing that I have found is a 12” pieceof 8 gauge bare copper ground wire from the hardware store. Theends are bent in short hooks with needle nose pliers and then thewire is hand formed into a loop and the hooks connected together tokeep it from spreading out when deployed. I attached a small pieceof orange barrier tape to keep the ring from getting lost in the grass.The ring shown at right has two of the 16 radials attached.

2. Sixteen Easy-to-Deploy Radials: I chose to use brightly colored 20 gauge solid insulated copper wire for my radials. The bright color minimizes trip risk, and the solid 20 gauge size facilitates attachment of the alligator clips (especially the screw on type). It also makes it easy to pack the radials for storage. While the ends of solid wire are more susceptible to breakage, they are also easily repaired by simply striping a little more insulation off the end and re-attaching. For this application a few inches will generally not matter much. Twisted red and white bell wire, or optionally pet boundary wire or similar bright, solid 20 gauge wire may be used. If twisted bell wire is used, it will have to be untwisted prior to cutting and installation. You will want to determine the length of your radials and whether you are going to use inverted L extensions when determining how much wire to purchase. While using the same color will work, using at least 2 different colors of wire will make deployment easier.

Each radial has an alligator clip installed to connect it to the radial ring. While they have some disadvantages when it comes to corrosion, alligator clips will make deployment MUCH easier, especially on your back, since they may be attached the radial ring using one hand by just briefly bending over.

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The alligator clip type that you use is up to you. I tried several types that I found on Amazon and determined that the 2” long screw type using plated steel was the best for me. If you use the screw type make sure that they come with the proper screws and have teeth that will grip the radial ring. While a soldered connection would be more reliable, screws are almost as reliable, are easier to attach, and allow maintenance in the field when a soldering iron is not available. While I tried to find stainless steel clips in an attempt to minimize corrosion, the only stainless steel screw type that I found did not have screws, and I could not locate stainless steel screws that would fit well. While I did not try it, soldering to stainless steel is said to require a special flux and technique to work well, so I do not recommend that type of clip.

I performed a month long corrosion test on several clips by leaving them submerged in simulated ocean water, and while there was some corrosion on theplated steel clips where they would attach to the wire andring, most of that corrosion could be easily removed byrinsing with clear water and wiping with a paper towel(see the picture on the right). All clips, including thestainless steel ones that I tried, exhibited corrosion of thespring inside the clip, although the spring still workedwell. Since this antenna is designed for temporaryoperation, corrosion should not be much of a problem.However, inserting a disposable plastic plate below the radials to elevate them above ground moistureand then covering the radial ring and clips with a cover such as a 9” cake pan should prevent much of the corrosion. Since the clips are inexpensive when purchased in bulk, buying enough to replace the clips in the future might also be a good idea.

The amount and color of wire to purchase depends on the length of the radials and how many colors of wires that you wish to use. While having all of the wires the same color can be cheaper if you purchase the wire in bulk, it can also make deployment a bit more confusing. Two colors of wire make deployment easier, and three even more so.

While radial layout does not need to be exact to be effective, I suggest laying out the radials in pairs, one across from the other, so that they will make a straight line. This helps to prevent confusion.

As shown in the picture to the right, radials are laid out inthree phases: 1) lay out 4 radials at approximate rightangles to each other (two pairs), 2) layout 4 more radialsbetween each of the initial 4 radials (bisecting the 90degree angles), 3) layout the remaining 8 radials betweeneach of the first 8 radials (bisecting the 45 degreeangles).

In the first row, all of the radials are the same color,which can make laying out the last 8 radials a bitconfusing if you are not careful.

In the second row, twisted red and white bell wire thathas been untwisted and separated is used with the first 8radials being white and the last 8 radials being red; thismakes layout much less confusing since you simplymake sure that there are no radials with the same color next to each another for the last 8 radials. This also means that you use the same number of red and white radials, so there is no waste.

Using three colors as in the third row example might also be a good idea. All of the red radials go between the white radials, and no two yellow radials are next to one another.

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3. Mount Connector Wires: I used two one-foot wires each attached to one of the bolts on the mount and attached an alligator clip to the other end. These wires are attached to the radial ring after both theradials and the triangular base assembly with attached coax have been put into place. While only one of these is really needed, I chose to use two for redundancy. If you only have one them, and if the connection breaks or the clip slips off, then the only radial you will be using with be your coax which will result in both poor SWR and poor performance and will also likely result in RF getting into your radio. It may still work, but it is not fun (I know this from experience).

4. Holding Down the Ends of the Radials: I formed a smallloop at the end of each radial. When deploying the radials onground I insert a brightly colored golf tee through the loopwhile standing up and then push the tee into the ground.Bright colored tees make it easy for you to make sure that allhave been picked up when you take down the antenna (teesare not good for lawn mowers). I used golf tees to minimizethe trip hazard since they pull up easily if tripped on. I recommend using short tees for hard ground and long tees for soft ground or sand. On hard surfaces like concrete, rock, or very hard dirt, I used zip lock bags filled with small pea gravel. Sand should also work, but could be more messy if a bag breaks especially during transport. I suggest using heavy duty bags to minimize breakage risk. Small containers of bottled water also work on level ground and my be used for drinking afterward.

5. Inverted L Extensions for 30 and 40 Meters (Optional). I desired theability to operate on 30 and 40 meters, so I constructed two extensions.The 30-meter extension used 11 ft of wire and the 40-meter extensionused 21-23 feet of wire depending on radial length. Make sure that youhave enough space to use these. While this is a bit longer than thecalculated length, it was necessary to achieve acceptable SWR readings.As shown in the picture to the right (with intentionally shortened wirefor photo purposes only) I used a rectangular piece of wood to attachabout 30 feet of mason line (red-orange) that was then attached to awire tie used as an insulator and then to the antenna wire (yellow). The antenna wire was then attached to an alligator clip that is used to connect the extension to the whip.

To use the extension, first collapse all of the sections. The top section ofthe antenna is then extended just enough to attach the alligator clip asshown in the picture to the right. Keeping the top section mostly insertedinto the next to the top section provides greater strength and should helpprevent permanent whip bending or kinking; it also keeps the clip fromslipping down the whip. All of the other sections are then extendedcompletely before gently stretching out the extension with the masonline/string. Next, the wood is then put over a low support. There is noneed to tie it off as the weight of the wood should be sufficient; just let it down to the ground gently and the shape will keep it from rolling. If no support structure is available, the rectangular piece of wood may be placed on the ground as far away as possible. It is important toremember that this extension places a considerable stress on a verythin antenna, so only use light weight materials for the extension andextend it only enough to get it away from the main antenna; you arenot trying to make it straight. Remember that while the extension doesradiate, its primary purpose is impedance matching, so it does not needto be very high or straight. Even with light tension, the antenna will bowconsiderably; this is OK as long as you do not permanently bend or kinkthe main antenna, so be very careful. When you have finished using theextension, be sure to release the tension in the line before collapsing thewhip. The picture on the right shows an example of what I found to bethe maximum acceptable bowing.

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6. Perimeter Barrier for Special Events (Optional).While the antenna works well, it can be a potentialtripping hazard. To help avoid this especially inpublic, an inexpensive barrier can be put up aroundthe entire installed antenna if needed. This methodwas used in a busy parking lot during the SolarEclipse QSO party and worked well except for oneadult who intentionally decided to duck under thetape (You can’t make anything fool-proof). I built 3short stands using 1/2” PVC pipe using a side outletelbow at the base, a tee fitting at the top to put thetape through, and caps at the ends of the legs to keepwater out (top left picture). The pipes are 2 to 3 feetlong. I also built one special taller stand with a crossconnector in the middle so that I could attach themason line of the inverted L extension if needed (topright picture). The stands were then positionedaround the antenna so that it and the inverted Lextension were enclosed and the tape was routedthrough the tees at the top of the short stands and thecross connector on the tall one (lower photo). Youmay want to modify this a bit to make sure that youcan have easy access to the antenna area foradjustment without having to duck under the tape.

7. Carrying Case (Optional). Ease of assembly is no good ifyou have to go looking for something or if you leftsomething at home, so you probably will need some typeof storage for the antenna. Since the whip is over 2 feetlong, finding something that everything will fit into can bea bit challenging. As shown in the picture to the right, Iused a bat bag that worked well. You may be able to useone of those long package wrap containers generallyavailable around Christmas time. FedEx sells a long boxfor transport that also might be useful for shipping. Thebags that are used to hold folding lawn chairs may also beused. In some cases, the container that was used to shipyou your whip might work.

As shown by the picture on the right, the container thatholds my back-up antenna is a long, low, translucentcontainer that also holds my perimeter barrier and still hasroom for a roll of coax should the need arise. While notshown, make sure to include the band chart and setupinstructions so you can adjust your antenna in the field. Itwould also be a good idea to include a container checklistto make sure that you have everything that you need whenyou need it.

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Radial Selection Considerations – Performance, SWR, and SWR/Band Chart

I only have test data from 3 different radial lengths: 5 feet, 8 feet, and 13 feet. The performance of each configuration was determined by comparing the configurations to my 130 foot end-fed antenna that is 40 feet in the air at the ends. While the comparison is somewhat subjective, it is based on comparing my typical percentile ranking in SKCC Sprints. Using ranking in the sprints eliminates band conditions as a performance variable since all participants had similar band conditions. Under these circumstances, the 5 foot radial configuration was about 70% as effective as the end-fed, the 8 foot (actually 7.75 foot) radial configuration was about 80-85% as effective,and the 13 foot radial configuration was about the same, or maybe a little less, than my end-fed antenna. The 8-foot and 5-foot versions received the most testing since I could leave them up longer. Since I have to put the 13-foot version on our parking pad, I could not leave it up for long which limited testing time.

The following summary chart was created using the SWR meters in a Ten Tec Eagle and a Yaesu FT-450D with the internal tuners disabled and a Diamond SX-200 meter utilizing the indicated lengths placed directly on ground/concrete. Remember that coax length, ground conditions, and nearby objects can impact the SWR.

Collapsed setting means to collapse the topmost number of sections indicated. For example, to set the antenna for 15 meter operation, collapse the top three sections, extend the fourth section completely, and then collapse the fourth section half way. All other sections are then extended fully.

As you can see from the charts, there is some variability in some of the collapsed lengths, inverted L extension lengths, and the SWR readings depending on the band and radial length. The SWR shown was the worst SWR measured in the segment of the band indicated. This antenna is very broad-banded and the SWR for each band segment indicated does not generally vary more that a few tenths. Note that the 13-foot radials were tested on a concrete parking pad and the ground conditions there were obviously a little different; this may explain the poor SWR on 40 and 10 meters even with whip/extension length changes. A built in tuner may be needed for some radial lengths, for some bands, or if the antenna is miss-adjusted or if the ground conditions are poor.

When using this antenna, always test the SWR at low power during initial testing and after any adjustment. Even with good band charts, it is very easy to miscount the number of sections when making adjustments. It is also veryeasy to fail to extend a section completely. To avoid this, I suggest that you hold the lower section with one hand while using the other hand to fully extend the section above. This also keeps the antenna from lifting off the ground if you have to pull up too hard.

While the radial length that you use is up to you (you can always make more radials later if you wish), I recommend starting with 8 foot radials as a good compromise in space requirements, performance, and SWR.

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Acquiring the Parts and Constructing the Basic Antenna

The Bill of Materials below is for the basic antenna with no options using sixteen 8-foot radials and the Firestik mount. Each leg is cut in half for easy transport. Prices for those things not included in the total should only cost $10 to $20 dollars more if you do not already have them. The price for the 40 and 30 meter extensions should alsoonly be a few dollars more, especially if wire is the only thing that needs to be purchased. Adjust your Bill of Materials to your requirements.

While the assembly of this antenna will be mostly intuitive for some hams, newcomers and those that like detailedinstructions might find the following helpful:

1. Order the whip, mount, and alligator clips. You will need at least 18 clips for the base antenna and another2 for the inverted L extensions. Buying more clips is a good idea in case one is defective, you have to replace one, or if you decide later to create another set of different length radials. If you cannot locate a local source for the appropriately sized Side Outlet Elbow, order it as well.

2. Take the mount with you to the store to purchase the long replacement bolts to make sure that they will connect the mount to the PVC mast. Purchase the other items on the list. Remember to get more wire if you are going to build the inverted L extensions; 24 feet of two conductor bell wire should be enough for both extensions.

3. Use a hacksaw to cut 12 inches off of the 10 foot PVC pipe to use as a mast. Cut the remaining 9 feet into four equal lengths (27 inches long) for the legs (My local Ace Hardware actually cut this for me for free).

4. Put one cap on the mast, and one cap on the ends of two of the half-legs.5. Put a coupler on the end of each of the two remaining half-legs.6. Insert the mast into one opening of the Side Outlet Elbow.7. Replace the two short bolts that come with the mount with the two long bolts in the materials list and

securely fasten the mount onto the mast using the lock washers and nuts that came with the mount. Make sure that the SO-239 connector is facing down. Insert the bolt with the screw/bolt head on the SO-232 side of the mount; this will minimize scraping your knuckles when attaching the coax later. See the picture on page 3.

8. Attach the mount with the two long replacement bolts about an inch above where the mast fits into the Side Outlet Elbow. Make sure that the mount is oriented between the other two outlets on the Side Outlet Elbow.

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9. If you are using a strain relief, attach about a foot of double sided Velcro strapping with a screw to the mast next to the end cap on the mast on the mount side of the mast. Note: the screw just holds the strap in place so it will not slip up and down the mast.

10. Assemble each leg by inserting one of the capped end half-legs into one of the end half-legs with the couplers attached and then completely insert each of the completed legs into one of the available Side Outlet Elbow openings. While you want the legs to be able to be removed easily, if you do not insert themcompletely into the elbow and the couplers, they may work their way loose and cause the antenna to lean or even fall over if a leg completely slips out.

11. For testing, put the completed base assembly on level ground and attach the whip by hand. 12. Extend the whip carefully and test the base for stability.13. If a strain relief is used, wrap it around the whip until it is slightly snug against the whip and the whip

appears to be vertical.14. Cut the radial wires to the proper length, and untwist and separate if using red and white twisted pair bell

wire.15. Strip about an inch of insulation off of one end of each radial and attach to an alligator clip as shown in

the picture on page 5. Of course, your clips design may be a little different, but if it is like mine, you can bend a small curve in the bare end to get it into the rear of the clip and up through the small hole and then wrap it clockwise around the screw before tightening. Needle nose pliers are good for wrapping.

16. Put a small loop at the other end and make sure that a golf tee will fit well.17. Hold the clip in your hand and gently wrap all but about a foot of wire around your hand.

18. Remove your hand from inside the wrapped radial, flatten the circularloop, and wrap the remaining wire around the radial bundle. The enddoes not need to be secured since the stiff wire will keep it mostly inplace and prevent most tangling. Then just put the radial in a zip lockbag for storage (Quart size is good for 5 and 8 foot radials, but you willwant to use a gallon size bag for the 13 foot radials).

19. Create the two mount/radial ring attachment wires by doing thefollowing:1. Cut two one foot wires.2. Strip 2 inches off the end of each wire and 1 inch off of the other end of each wire.3. Attach an alligator clip to each of the 1 inch stripped ends.4. Loosen one bolt at a time on the mount and snugly wrap the two inch stripped end in a clockwise

direction between the nut and the mount and re-tighten. 5. Wrap the wires loosely around the mast section to keep them out of the way during storage and

transport.20. To create the radial ring, use needle nose or similar pliers to bend a hook

about an inch long at the each end of the 8 gauge ground wire. If possible,bend the hooks at right angles to each other – it makes hooking themtogether easier.

21. Bend the ground wire by hand into an approximate circle and hook thetwo ends together. Attach something bright like orange marking tape to thering to help keep you from loosing it in the grass.

Enough information to construct the optional Inverted L Extensions and thePerimeter Barrier is contained in those sections above.

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Homebrew Vertical Set-Up Instructions

1. Position the copper radial ring in the center of the radial area (with the protective plastic plate beneath it ifdesired).

2. Attach the radials to the radial ring using the attached alligator clips. As each radial is removed from the storage bag and attached to the radial ring, unwind and straighten it before attaching. Radials should be attached in pairs with one across from the other to keep them in a straight line.1. Attach the first group of 4 radials (2 pairs) to the radial ring at right angles to each other and secure

the ends with golf tees.2. Attach the second group of 4 radials to the radial ring in between the first group of 4 radials (bisecting

the angle formed by the first group of radials) and secure the ends with golf tees.3. Attach the remaining 8 radials to the radial ring between the first 8 installed radials (bisecting the

angle formed by the each of the first 8 radials) and secure the ends with golf tees.3. Assemble the 2 mast assembly legs. The caps should be on the ends of the legs (with the couplers in the

middle if used).4. If the radial attachment wires attached to the mount are wound around the mast assembly center section

for storage, then unwind them to free them.5. Layout the coax with one end near the radial ring.6. Attach the coax to the mount on the mast assembly center section. It is easier to do this now than later

since it may be done while standing up. 7. Insert the 2 mast assembly legs into the openings in the side outlet elbow that is used as the bottom of the

mast assembly center section. Make sure that these are secure.8. Place the completed mast assembly with attached coax next to, but not on top of, the radial ring with the

ring between the V formed by the legs.9. If inverted L extensions are to be used, position the legs so that the extensions will be directly between the

V formed by the legs.10. Make sure that the mount is directly between the 2 legs, and that the coax is not under a leg.11. Attach the 2 radial attachment wires to radial ring using the alligator clips on the end of each.12. Insert the whip through the stress relief strap at the near the top of the mast and screw it into the mount by

hand.13. If desired, cover the radial ring and attached alligator clips to protect them from the weather.14. If using 20-6 meters, extend the whip to the length shown on the band chart. To make sure that a section

is completely extended, remember to hold the section below in one hand while firmly pulling them apart.

15. If using a 40 or 30 meter inverted L extension assembly, then do the following:1. Unwind the wire/wire tie/mason line assembly leaving the mason line attached to the wood block and

position the alligator clip near the mast and the other end (with the block attached) away from the mast and between the two mast legs.

2. If using a low support structure, toss the block over the support and let it fall to the ground.1. Extend the upper whip section just enough to attach the alligator clip and attach the clip.2. Carefully extend all of the other sections of the whip.3. Carefully wind the excess mason line onto the block just enough to pull the extension wire away

from the whip; DO NOT PULL THE LINE TIGHT.4. While holding the mason line in one hand, drop the block and it will unroll. DO NOT TIE OFF

THE MASON LINE.3. If no low support structure is available, then:

1. Extend the upper whip section just enough to attach the alligator clip and attach the clip.2. Carefully extend all of the other sections of the whip.3. Stretch out the block with attached mason line just enough to pull the extension wire away from

the whip and leave it resting on the ground; DO NOT PULL THE LINE TIGHT.16. Attach the antenna to the radio and check for low SWR before starting to transmit.

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Version History

Version 1

This was a proof-of-concept prototype using the MFJ whip. All other parts were in my junk box. It used four 7-foot radial assemblies with each assembly made from 3-conductor rotator cable (12 radials total). While the antenna worked reasonably well, the aluminum box center section was not strong enough to be useful (the box would bend in even a light wind). This version was disassembled and the parts reused.

Version 2

This version was very robust and was used in the “Domestic Field Day Expedition” to Syracuse, NY in 2017. It did not use a special whip mount. Instead, a bolt of the correct size and thread pitch was used to attach the whip. Abulkhead mount was used to attach the coax. Four pairs of 12-foot speaker wire radials were used (8 total radials) using soldered ring terminals attached to a single ground connection bolt. The ground connection bolt was connected inside the large PVC body using a jumper to the coax mount ground connection. The center pin of the coax mount was connected to the whip attachment bolt inside the body using jumpers. While this version was robust and reliable, it more expensive that I would have liked (the large PVC fittings cost more). It had a large number of parts, and it was much more difficult to fabricate involving considerable soldering and working in tightspaces. This antenna is still in use in Syracuse.

April 3, 2018 Easy-to-Build Homebrew Portable Vertical Antenna-4th Version Page 12 of 13

Version 3

Since version 2 worked much better than I had anticipated, I wanted to see if I could create a 3 rd version that would also be easy-to-build. This version uses the same V shaped mast as the 4 th version, differing primarily in theradial assembly. In the 3rd version, eight 20-gauge solid insulated radials are attached to the mount attachment bolts. 4 radials were connected to each bolt using 2 extra washers and a wing nut. No special connectors were used; the wires were just stripped about an inch, bent into U shaped hooks, and then hooked over the bolt betweenthe extra washers. When all 4 radials were hooked, the wing nut was tightened. While this version was very easy to build and the least expensive of my versions, its was not as effective as I wanted and the 4 radials per bolt appears to be about the limit before radials started slipping off the bolt both before or as the wing nut was tightened. Also, the radials had to be routed under the legs to keep them close to the ground, and this and the attachment process required getting down on the ground and a considerable amount of bending over, often requiring the use of both hands at the same time. This made deployment stressful and uncomfortable.

In an effort to provide a more effective antenna, I created an alternative 16 radial version using a stainless steel sink stopper. While this worked, it was very difficult to both deploy and store (I used an empty coffee container for a storage support). This 3rd version led to the 4th version that was designed to be both effective and easy to deploy. The 3rd version parts were re-used in the 4th version.

Special Note: While not especially relevant for a portable antenna, using the stainless steel sink stopper version might be useful in a semi-portable installation where the radials are permanently buried, provided that stainless steel nuts and bolts are used. The sink stopper could then be covered with something like a fiberglass rock or other lawn art. An irrigation valve box or similar item would also allow installing it flush with the ground.

Conclusion

While no antenna is perfect, I believe that this design can be useful in many situations both in the field and for those with limited space requirements. Any suggestions or comments that would help to improve this antenna design or these instructions would be appreciated.

73,Charles Kight, AI4UNai4un@arrl.net

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