Tag Archives: Antenna

A Vertical to Go

By Shel Radin KFØUR

Years ago when I started operating QRP portable, I was in search of the “right” antenna.

But let me first describe my definition of QRP Portable, as it can mean so many things. In my case, it is hiking with a small backpack for the day on the Colorado Rocky Mountain trails near my QTH in Colorado Springs. I’ll hike for an hour or so, find a place with a beautiful view (required!), set up quickly and operate for a number of hours.

My antenna requirements were relatively simple (at least in my mind). They included:

  • Cover 10-40 meters
  • Be easy to set up and tear down…especially tear down as I usually wait too long to clear out when thunderstorms are approaching and need to make a fast exit.
  • Be lightweight and easy to carry, so I can keep the overall backpack weight down, and have room for another bottle of water and peanut butter and jelly sandwich.

An internet search led me to a plethora of possibilities, but the one that caught my eye was a design by Phil Salas, AD5X. Actually after Phil’s original design was published, there were a number of variants found.

It was basically a 12 foot tall vertical, center loaded (coil in the middle), and some radials on the ground. I liked the simplicity of it.

As I recall, the original design used plastic sprinkler risers as the vertical part, as they just screw together. Wires were run up their sides to make the radiating part of the antenna. Other variants used metal rods screwed or clamped together, instead of plastic risers.

So I built one of the metal rod versions. It worked, but I didn’t like the number of pieces involved. It didn’t fit my requirement of easy set up. And there were pieces that could be dropped and lost. I’ve witnessed too many times that a dropped screw or clip seems to get absorbed by the earth, never to be seen again.

Fast forward a bunch of outings and I came up with a solution that met all of my criteria, and by the way, works very well. I think I built 4 versions before I settled on this one.

Antenna Description

It’s still a 12 foot antenna, center loaded…but it’s built with fewer components.

The bottom 66” is a heavy duty telescoping whip from BuddiPole. It has a 3/8 x 24 thread on the bottom, which is very handy.

The top 6 feet is a light duty telescoping whip, the kind you used to find at Radio Shack for $6. I don’t think they sell them any longer, but should be available elsewhere. At the time of this writing, Buddipole sells one similar with a ¼” x 20 threaded bottom.

The coil in the center is a 2 inch diameter coil, 10 turns per inch. I used a coil length of 5”, but this could be shorter as I’ve never used all of it on any band.

To hold the whole thing up, I used a PVC tee from the local home improvement store (Home Depot in my case). This sits on a 12” rod that you bang into the ground using a nearby rock, or instead Velcro to small bush or branch. I always have some Velcro with me.

Let’s take a look at the details of how it’s put together.

Antenna Construction

The first thing to know is that there is nothing critical with any of these parts. This is what I found at the store when I went looking. Feel free to substitute just about anything, including the size of the coil.

There are only a few things to build. Here’s a quick overview:

There’s a base made from a ¾” PVC Tee. Figure 1 shows it put together. Figure 2 shows it piece by piece. The 66” BuddiPole whip screws into the top into the brass fitting. It already has the correct 3/8” x 24 threads.

KF0UR Vertical: T-connector

Fig. 1

The components of the base, shown in Figure 2 are as follows:

KF0UR Vertical: Base Unit

Fig. 2

Here’s the center coil which is supported by a small dowel and some brass tubing.

KF0UR Vertical: Center Coil

Fig. 3

STEP-BY-STEP CONSTRUCTION

The Base

1. Solder leads to an RF connector. It can be an SO-239 or BNC. I use a BNC because my LMR-100 or RG-174 coax has BNC connectors on it.

2. Mount the RF connector on the PVC Plug. You can solder the leads after you mount it, but I found it easier to get the leads on first.
3. Insert the Plug into the side of the PVC Tee. If it’s a smooth plug (not threaded), put a drop of PVC cement on it to hold it in place. Not much is needed. Note: every time I look, the design of these plugs change. Remember…nothing is critical in the design.

4. Solder the lead connected to the center of the RF connector to the brass fitting. I just used a 100 watt soldering gun and soldered it to the end of the brass fitting.

5. Screw the brass fitting into the PVC adapter.

6. Solder the lead connected to the ground of the RF connector to a lug.

7. Make a ground ring as shown and connected it to the ground lead from the connector.

KF0UR Vertical: Ground Ring

Fig. 4

8. Slide the ¾” to ½” PVC bushing into the bottom of the PVC Tee. Use a drop of PVC cement to hold it in place. This bushing has ½” threads on the inside.

9. Screw the 4” x ½” nipple into the bushing at the bottom.

10. Drill a hole in the end cap that screws on the bushing. This is so it fits over the support rod that you bang into the ground and holds up the vertical. The rod I used is 3/8” threaded, so I drilled a 3/8” hole.

11. Screw the end cap with the hole onto the end of the 4” x ½” nipple.

The Coil

1. Cut a ¼” dowel 5” long.

2. Cut two 2¼ “ pieces of 9/32” hollow brass tubing. This tubing fits over the end of the Buddipole whip snuggly. And the 6 foot light duty whip fits inside the tubing nicely. I found the tubing at a local hardware store (not a home improvement center). If you use something a bit bigger, you can always put a few dimples in it to make it more snug.
3.
4. Place a brass piece onto each end of the dowel, so that the dowel is about halfway into each brass piece. Glue or epoxy it in place. In the end, you have a dowel with brass tubing on each end and the overall length, tip-to-tip is approx.. 8 ¼”.

5. Solder a 6”-7” lead onto one of the brass tubes. This will be the bottom of the coil assembly. I used small ground braid for its flexibility.

6. Put some kind of clip on the end of the lead (mini-gator, easy-hook, etc.). This will clip onto the coil to short out turns as needed for each band.

7. (optional) take a screwdriver and push in every other turn on the coil. This just gives you more room for the clip.

8. The coil I used is 5” long, 2” wide, and 10 turns per inch. Unravel about 1.5 inches of lead from the coil from each end. Place the dowel and brass assembly in the center of the coil and solder each unraveled end of the coil to the brass tubes. Now the dowel is in the center if the coil, and is supporting the coil as each end is soldered to the brass tubing.

The Rest

Cut some radials. There are as many articles on radial length and number as there are types of wire. I used six 12’ radials because I read someone else used them with success. Six radials are a manageable number and fits the requirement of easy set up and tear down. I chose bright yellow so they are easily seen and a jacket that does not kink (it might be Teflon). But feel free to experiment.

Put a clip (alligator, mini-gator, easyhook, etc.) one end. When deploying them, simply clip them to the ground ring on the PVC base.

Get a rod to stick in the ground. I use a 12” x 3/8” threaded rod, with one end ground to a point, to make it easier to bang into the ground.

Putting it up on site

1. Bang the 12” rod into the ground. A nearby rock makes a great hammer. Leave about 4” sticking up out of the ground. Or sometimes I just Velcro it to a small bush.

2. Thread the 4” x ½” PVC nipple with the end cap onto the bottom of the PVC base. Place the PVC Tee assembly, nipple first, over the rod.

3. Screw the 66” BuddiPole whip into the brass fitting on the top of the PVC base.

4. Slip the brass tube on the bottom of the coil on to the top of the BuddiPole 66” whip.

5. Slip the 6’ light duty whip into the brass tube on top of the coil assembly.

6. Clip the shorting lead on the coil to the approx. position for the band you are going to work.

7. Extend both whips fully.

8. Lay out the radials and clip them to the ground ring on the base.

9. Attach the coax.

10. Tune the antenna by moving the shorting lead on the coil as needed. Some experimentation is required to find the right spots. Once found for each band, I marked them with my XYL’s fingernail polish. This will change somewhat as you move locations and the ground conditions change, but it’ll get you close every time.

That’s it. There’s not much to it, and nothing very technical. Feel free to experiment with other construction ideas. Note that when the antenna is up, it’s not absolutely vertical. This is OK.

KF0UR Vertical: Mounted in small bush

Fig. 5. Vertical Velcro’d to a small bush on Spruce Mountain, CO.

KF0UR Vertical: Vertical mounted to fallen branch

Fig. 6. Velcro’d to a fallen branch on Mt. Herman, CO. Note the radials clipped to the ground ring. I put a small piece of Velcro on each radial to keep them tidy when put away.

KF0UR Vertical: On Mt. Herman

Fig. 7. Vertical in use on Mt. Herman. That’s Dan KØUIF enjoying the view and the QSOs.

KF0UR Vertical: Compact Storage

Fig. 8. Here’s how it all gets compactly stored.

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A Vertical With a Difference

By Peter Inskeep NO2D

Almost everyone is familiar with vertical antennas. Long, thin poles that reach skyward. They promise omni-directional reception and transmission. They take up very little space. They are ideal for small plots of land. However, they do have some downsides. If ground mounted they invariably require an extensive network of radials. The more, the merrier, they say. Sometimes buried and sometimes laid out on the surface with hopes that no one will trip on them or mow them down. Multi-band designs can get quite complicated. Another common complaint about verticals is that “they radiate equally poorly in every direction.” That last quote is direct from a sales person at a well known amateur radio retail dealer. Generally speaking, because of their low radiation angle they are not that good for close in work.

Figure 1. Peter Inskeep NO2D’s homebrew HF vertical is on the right corner of his deck.

So, why bother with verticals? A good commercial built vertical can provide multi-band operation without the need for a tuner. A good commercial vertical can also be very expensive. Some commercial vertical companies claim that their verticals do not need radials. Take that with a grain of sand. Home brew verticals, on the other hand, can be built very inexpensively, especially if one wants to use it only on a single band. To get around the need for dozens of radials a vertical can be mounted above ground, when it will require only a few (4 will do) radials. Mounted above ground it is generally called a ground-plane vertical.

Taking the positives and the negatives into account I decided to build a home brew vertical to see how well it might work. Rather than go out and buy aluminum poles to act as the radiator, I decided to just use a piece of 14 gauge wire. My design frequency was 14.035 MHz. Think of a wire sixteen plus feet long. Pieces of wire that long usually don’t stay up in the air by themselves. How could I support this wire vertically?

Fortunately, there were some fiberglass poles in the garage left over from my defunct Lightning Bolt Quad, which bit the dust a few years ago in a violent wind storm. The quad had 16 fiberglass spreaders. Three of the spreader poles when fit together made a mast about 20 ½ feet long. By the standard formula (468 / Freq in MHz.) half wave dipole resonant at 14.035 MHz. should be 33.345 feet long. To determine the length of a quarter wave vertical, simply divide 33.345 by 2 to arrive at 16 feet and 8 inches, the appropriate length for the quarter wave antenna. The formula above is for a half wave dipole, so just divide it by 2.

Figure 2. Attaching the feed line to the antenna components. Upper hose clamp holds the bottom of the driven element. Lower hose clamp connects the radials to the ladder feed line.

Strip the 14 gauge wire and cut it to 16’ 8”, plus a few more inches. Tape one end to the top end of the fiberglass poles, ie., mast. Run the wire down the mast, taping it for support at various places. The bottom end of the wire was about 4 feet from the bottom of the mast. Tuck the bottom end of the radiator under a hose clamp to make it secure. Then attach another hose clamp to the mast about an inch under the upper hose clamp. Stick a short piece of 14 gauge wire through that hose clamp, making sure it does not touch the antenna radiator. This is used to connect the ground radials, and one side of the ladder line. Cut 4 radials from the same spool of 14 gauge wire. Strip any insulation that may be on the wires, as insulation can lower the resonant frequency. All should be the same length as the radiator, 16 feet and 8 inches, plus some surplus for tying them off to insulators. Solder one end of each radial to the short wire below the lower end of the radiator.

As this antenna is designed to be a ground-plane, it must be mounted above ground. It should be mounted high enough so that the radials do not inadvertently hit someone walking underneath them when extended. I chose to mount this 20 ½ foot long pole to the railing of my back deck. Since this was an experimental antenna I just used rope to tie it to the railing of the deck. (This step requires permission from the boss, which I managed to obtain.). I connected a feed line made of window line. It can be whatever length is necessary to reach from the antenna mast to the rig tuner. A tuner is required for this antenna. One side of the window line is soldered to the radiator stub at the upper clamp. The other end is soldered to the short wire that connected with the 4 radials at the lower clamp. At this point envision a long non-conductive pole with a wire running vertically from the top down to the feed line. Also imagine 4 radials spread out around the deck in roughly 4 directions so no one would run into them.

In my case the window line went in through a back basement door to the tuner in my shack. Getting window line into a house can be difficult. Some folks will terminate it with a 4:1 balun outside the house. Then they run coax from the balun in to the tuner. Either way, some ingenuity is required to get the feed line into the shack and to the tuner.

A properly constructed vertical antenna can be fed directly with 50 ohm coaxial cable. Almost all are, commercial or otherwise. They should work on their design frequency. They won’t work well, or at all, on other bands, unless they are designed as multi-band verticals. Using window line (or ladder line if you have the patience and skill to build it), on the other hand, allows the antenna to be used on other bands than the one for which it was designed.

One of my tuners is an LDG AT100 ProII. The window line terminates in a small 4:1 balun, which is then connected to the LDG tuner with a short piece of coax. Using this setup, it tunes very easily to 1.0:1 on the bottom end of the 20 meter band. It also tunes to 1.0:1 on both 17 and 15 meters. 12 meters is not so good, at 1.7:1. 10 meters does great at 1.0:1. Would you believe that it also tunes on 30 meters? Actually, it does get down to 1.3:1 SWR on 10.115 Mhz. It even tunes down to 1.0:1 on 40 meters. I doubt that it does very well on that band, though, so I seldom use it there.

On 20 meters it often equals, or out performs, my doublet up at 30 feet, or my dipole, also at 30 feet. Sometimes it is better, and sometime not. On the other bands the story is more mixed. It occasionally works better, but more often than not the doublet, tuned through the same LDG auto-tuner, will outperform it.

It might be an ideal inexpensive antenna for someone who wants to operate several bands but does not have the room or physical supports for a long wire antenna. It gives me another weapon, especially when I am searching for DX. They say that the main strength of a vertical is its low angle of radiation, which is good for hunting DX. A dipole or doublet, on the other hand, especially at a low height of 30 feet, does not really have a very good low angle of radiation, and may not be as effective as a vertical for DX.

Figure 1 shows an overall view of the vertical attached to the corner of the deck. The radials are difficult to see, but stretch out, generally speaking, from the mast just at the height of the deck rail, well above head level. Spread the radials out as equally as you can.

Figure 2 shows how the window feed line is attached to the mast. Note that the end of the radiator, coming down the pole, goes under the hose clamp and then directly to one end of the feed line. The other end of the feed line goes to the short 14 gauge wire that is under the lower hose clamp. There is no connection between the upper hose clamp or the radiator, and the lower hose clamp, which serves to secure the 4 radials as well as the other side of the window line.

This is not a difficult antenna to build if one can find a suitable mast. Crappie fishing poles are said to be effective for this purpose. If you have or can get a 17 foot long piece of aluminum or copper, by all means use that instead of the wire. It should work even better.

The two keys are first, design it as a ground plane vertical to avoid having to lay out dozens of radials. Second, use window line, or build your own ladder line so that it can be a multi-band antenna. My best DX with this antenna so far? South Cook Islands, Croatia, Germany, Belgium, and Chile. All with 5 watts or less. In some cases my dipoles or doublet will outperform the vertical. In other cases, the vertical wins. Nice to have all three to choose from.

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