In a previous post, I mentioned an antenna of mine that went missing. The antenna in question was a variation of my old Dollar Store Special. After I built a replacement, I found the original in my truck. No problem; as the name suggests, it wasn’t a huge monetary investment. This antenna is just another example of what can happen with some extra speaker and too much time on my hands.
The original Dollar Store Special (circa 2005) was the first of several projects to see if I could build a usable antenna from a 50-foot length of inexpensive speaker wire. The resulting antenna was a 50-foot radiator and some counterpoise wires configurable for 40M, 30M, and 20M. I used one of these for years as a backup antenna. As with all random wire antennas, it requires a tuner and, of course, some way to get one end up in the air.
For this version, I went with a 50-foot radiator and two 25-foot radials. Besides being more simple to construct, it adds a little more flexibility. Space permitting, I can use the 50-foot wire in an inverted L, inverted V, or sloper configuration. When I need a quick way to get on the air, I can use a 25-foot radiator with a 25-foot counterpoise. (Elecraft documentation often recommends the 25-foot wires as a simple field antenna. )
I refer to this antenna—with tongue firmly planted in cheek—as the Dollar Store Special 2.0. That makes it sound like a bigger deal than it actually is. I should also note that I can no longer get speaker wire at my local dollar store. I have to spend a few dollars more now, but I kept the name anyway.
Construction is as easy as it gets:
Get a 50-foot length of two-conductor speaker wire. I use some inexpensive 24 gauge wire.
Separate the two conductors.
Cut one of the 50-foot wires in half.
I added a spade lug on one end of each wire and made a small loop in the other end.
I also added some Goop® sealant/adhesive to hold the end loops together and provide some strain relief to the spade lugs.
The 50-foot radiator and two 25-foot radials cover 60M through 10M using my KX3’s internal tuner. Feeding it through a 4:1 unun, I can cover 80M through 10M. A 9:1 unun works well with this length also.
With a 25-foot radiator and a single 25-foot radial, my KX3 covers 40M through 10M with no problems. Adding in a 4:1 unun makes this a Rybakov 806 antenna that covers 60M through 10M. If you’re so inclined, you could partially unroll the 50-foot wire and use it as a second radial.
These results, of course, are highly dependent on the tuner you’re using. There’s nothing special about the 50-ft length. You can trim the radiator back to a length that provides an easier match. I stayed with the 50-foot length since I wanted to make use of the entire pool of speaker wire for these projects. Go with whatever works for you.
I’ve had good results with both configurations, and I have been impressed with the 25-foot radiator and 25-foot radial configuration. Although it’s slightly compromised on 40M, it seems to get out pretty well.
There’s nothing at all magical about this antenna; after all, it’s just three pieces of cheap wire. However, it makes a decent backup—or even a primary—antenna kit for portable use.
As I was writing this, I jotted down two more ideas for speaker wire antennas. Somebody stop me!
I’ve been intrigued by the half-square antenna for some time now. I don’t have the real estate to put one up at home, so I built one for portable use. Like my other speaker wire projects, this antenna is built from a 50-foot length of cheap, two-conductor wire.
You can think of the half-square as two quarter-wave verticals spaced a half-wavelength apart. It provides some gain over a quarter-wave vertical and has a low take-off angle. The half-square has a bi-directional pattern with lobes broadside to the antenna and nulls off of the ends.
Normally, the half-square is fed with coax at the top of one of the vertical elements and functions as a single-band antenna. The coax should be kept perpendicular to the vertical leg, to avoid interaction. That arrangement, however, would be somewhat awkward for a portable antenna.
For expediency in the field, I went in a different direction. I decided to feed it at the bottom of one of the vertical legs, which is a high impedance point. I use a 9:1 unun to reduce the high input impedance to something easier for a tuner to handle.
I designed this antenna for the 20M band, but I wanted to use it on other bands as well. By using the 9:1 unun to feed the bottom of the antenna, I’m able to squeeze some more bands out of it. A tuner is required, of course.
Refer to the accompanying diagram to help make sense of the following steps.
Separate the speaker wire into two 50-ft wires
On one of the wires, install a spade lug at one end. This will be the connection to your matching device)
From the spade lug, measure up 16′ 7.2″ and make a small loop using two small zip-ties.
From the second wire, cut a length that is about 16′ 9″ or so.
Strip and splice the smaller wire to the end of the larger wire. After soldering it, I covered the splice with heat-shrink tubing.
Next to the splice, make another small loop, using two zip-ties.
At the end of that wire, twist the wire to form an attachment loop. When you do this, make sure you have 16′ 7.2″ from the splice to the attachment loop.
I applied some Goop® adhesive to the loop at the end of the wire to hold it together. I also added Goop® to each of the other attachment loops.
As is my usual practice, I added some Goop® to where the wire enters the spade lug to add some strain relief.
At this point, the antenna is finished. You can, however, cut the leftover wire in half to make two radials for 20M (approximately 16 feet, give or take). I installed a spade lug on each of these wires and twisted the other ends to make a small loop. You guessed it; I put Goop® on these wires, as well.
[Update (6/17/2020) – After initially publishing this post, I received some great feedback from readers. As a result, I have updated, clarified, and expanded this section.]
For my first couple of outings with this antenna, I used a 9:1 unun as a quick and dirty way to get it on the air. I run about 18 feet of RG-8x coax from the unun to the radio. There’s nothing particularly critical about the coax length, but I would recommend a minimum of 16-feet for 40M and up. The exact length of the radials isn’t critical either since they’re laying on the ground. In fact, you can probably use the antenna without them. In this case, you’re relying on the coax shield for the counterpoise.
While the 9:1 worked fine, there are more efficient ways to match this antenna. I plan to continue experimenting with other methods to match the high-impedance input on 40M and 20M.
I haven’t tested them myself, but the end-fed halfwave tuners from Pacific Antenna and QRPGuys should work on 20M and 40M. They use a parallel resonant circuit and are designed to match an end-fed halfwave (EFHW) antenna.
An EFHW transformer, like the ubiquitous 49:1 transformer, should also work. You will likely need to do some pruning on the antenna to get the SWR where you want it.
Finally, a simple L-Match antenna tuner with a tapped inductor in series and a variable capacitor across the output looks like it may be the best solution for me. It should handle the high impedances on 40M and 20M, and work on other bands like a random wire tuner. This will definitely be part of my next round of experiments.
Deploying this antenna is a snap and takes me about 5 minutes. I use two collapsible poles to support it. I attach one corner to a partially-extended 28-foot Jackite pole. The feed point of the antenna is about 3 feet off the ground.
I use a 20-foot Black Widow pole (actual length about 19.5 feet) to support the other end. I support this pole with an appropriately-sized screwdriver shoved in the ground. The handle of the screwdriver fits snugly inside the bottom section of the pole. After attaching the other corner of the antenna to top of this pole, I extend the pole and remove the bottom cap. Next, I walk the pole back until the horizontal section is taut. Then, I just shove the screwdriver in the ground and place the pole over it.
With appropriate trees nearby, you might be able to eliminate one or both of the poles. I’m not usually that lucky.
Results of Field Testing
I was pleased with the results of my initial field tests with the half-square. The internal tuner in my Elecraft KX3 was able to load the antenna from 80M through 6M. (Since the antenna’s input impedance is low on 80M, I wouldn’t recommend using the 9:1 there.) The SWR was 1.2:1 or better on all bands with the tuner.
During my first outing with the half-square, I was able to make contacts on 40M, 20M, and 15M at 5 watts with no difficulty. The antenna is a half-wavelength on 40M, and it appears to play well on that band. I had numerous Reverse Beacon Network spots on 40M showing a signal-to-noise of 20db or better.
I also used it in the field during a recent QRP contest with similar results. Signals were strong on 40M, and I worked Georgia and Quebec on 20M.
This was hardly a rigorous scientific evaluation, but I’m happy with this antenna so far. One of these days, I’d like to do some modeling to see what the radiation patterns look like on the various bands. In the meantime, I’ll do some more experimenting with impedance matching.
This was an easy and fun project. It certainly made good use of a roll of cheap speaker wire. After using this antenna in the field a couple times, I have officially added it to my arsenal of portable antenna options.
I haven’t been posting much here lately. The COVID-19 pandemic and other family obligations have been cutting into my ham radio activities. Nevertheless, I do have a few projects in the works.
A few weeks ago, I started another project in my ongoing series of speaker wire antennas. This one will be a variant of the bi-square antenna. This antenna has the potential to be a little more field-friendly than the delta loop I tested last month. It’s all built; I just need to get out somewhere to set it up and see how it works.
I’ll file my next project under the category of Old Dogs/New Tricks. Back in December, I bought a Kenwood TH-D74a HT. That gave me the ability to reach a nearby D-Star repeater. This week, I purchased an MMDVM hotspot to go along with it. I plan to spend some time in the coming days getting it set up. I’m hoping to be able to eventually connect to the DMR talk groups used by my ARRL section and local ARES-RACES groups. Fortunately, my local group has some experienced hotspot users I can consult if I run into any snags. Wish me luck.
Sadly, our camping season with our little QRP Camper is off to a late start. State park campgrounds in our area have been closed due to pandemic. We have reservations at a state park in Maryland next month, however, and it looks that might be our first trip of the year. I’m looking forward to a little QRP-portable operating from the camper.
My local QRP club has started making plans for Field Day. We have a set of social-distancing guidelines we’ll be following this year. We’ll be limiting the number of participants, keeping our tents at least 10 feet apart, and eliminating common eating areas. Also, we won’t be sharing stations and equipment. This year’s Field Day will be different, for sure.
Other than that, I’ve been active on our local ARES-RACES nets, and I have been checking into the Pennsylvania NBEMS Net on Sunday mornings.
You can also find me on 40M or 80M CW in the evening. I usually hang out around the SKCC watering holes.
I’ll be posting more on all of this stuff in the coming weeks. Until then, stay safe, and I’ll see you on the air.
[This is an updated version of an article that originally appeared on my QSL.NET website.Although it’s twenty years old, I still occasionally hear from people who have built similar tuners.]
Antenna tuners (more accurately referred to as “transmatches”) make great homebrew projects; they are reasonably simple to build and, when finished, provide a useful piece of equipment. Every shack should have (at least) one. I built this one a couple of decades ago, and it’s still in use.
For this project, I decided to try my hand at building a Z-Match tuner from scratch. This type of tuner has been around for a while. While the Z-match can take on several variations, what distinguishes it from other circuits is that it is a resonant circuit that uses a fixed inductor.
Z-Match tuners became very popular within the QRP community years back, thanks primarily to articles in QRP journals by Charlie Lofgren W6JJZ and the emergence of Z-Match tuners in kit form. Emtech sold its wildly popular ZM-2 kit commercially and the NorCal QRP Club began selling their BLT tuner kit (a W6JJZ design) like hotcakes.
Some Pros and Cons
Why the popularity? Here are some advantages that the Z-match design offers:
Matches balanced loads without the use of lossy baluns.
Being a parallel resonant circuit, the Z-match can provide some band-pass filtering for your receiver and harmonic attenuation for your transmitter.
A well-designed Z-match tuner has a high Q and is more efficient (less lossy) than other types of tuners.
The fixed inductor simplifies construction (no taps or rollers needed).
Using a toroid inductor and some small poly-film variable capacitors, the Z-match can be built into a very compact package. This sort of thing usually appeals to QRPers.
There is, of course, no free lunch here. Here are some disadvantages of the Z-match design:
Tuning is usually very narrow and can be a bit touchy sometimes to tune up
The range of impedances that can be matched is not as great as in other designs, such as the “T” configuration.
Design and Construction
I make no claims of originality for anything in my version of the Z-match. I based it on a classic design which was first appeared in SPRAT #84 (see the G3YCC web site for a schematic of the original design). This design, by the way, is similar to the one used in the Emtech ZM-2.
I incorporated a few modifications in my version, based on an article by W6JJZ (“The Z-Match: An Update”, QRP Quarterly, July 1995, pp 10-11). First, instead of the T-200-2 toroid specified in the SPRAT article, I used a T-200-6 core. W6JJZ recommends the Type-6 core over the Type-2 because it provides a higher Q over most of the HF range. The number of turns has to be adjusted for the Type-6 core, due to differences in permeability. Here again, I went with W6JJZ’s suggested turns count. Another reason for choosing the T-200-6 core was that I happened to have one in my junk box. How convenient!
The coil was wound using some #22 solid hookup wire (from Radio Shack) which I had laying around. The secondary winding is wound between the turns of the primary to ensure tight coupling. I added a toggle switch to ground one side of the secondary winding to accommodate single-ended loads (like a random wire). A piece of styrofoam was glued to the bottom of the enclosure to provide some support for the toroid and to keep it away from metal surfaces.
Another W6JJZ modification I used was the inclusion of a DPDT (center off) toggle switch to provide some flexibility with the input capacitor. Using this switching arrangement, I can select between one section of the capacitor, both sections in parallel, or both sections in parallel with a fixed 470pF mica capacitor. The extra input capacitance can sometimes be helpful on the lower frequencies.
The capacitors are poly film variable capacitors (2 sections @ 365pF each), which were originally purchased from Mouser Electronics. Unfortunately, Mouser no longer carries them, and I don’t know of another commercial source. I should have purchased a truckload of them when they were available! Similar capacitors with smaller values are still available if you look around.
The SWR bridge I used is a Dan Tayloe LED SWR indicator from a kit that was offered years ago by the Arizona scQRPions. It uses a resistive bridge circuit with a single LED to indicate a null when the bridge is balanced. For the 50-ohm resistors in the bridge, I substituted 2 100-ohm, 1-watt resistors. The bridge will handle a typical 5-watt QRP rig without flinching and could probably handle a bit more than that.
The whole thing was packaged in an enclosure which measures 3 x 5 x 2 inches. It certainly could have been built into a smaller package, but I had this enclosure on hand and decided to put it to use.
On the Air
To use the Z-Match, adjust the capacitors for a null in the background noise in your transceiver. That will get you close to a match. Then, switch in the SWR bridge, apply some RF, and tweak the capacitors for minimum brightness on the LED. There may be some interaction between the two capacitors, so you might have to go back and forth between them a time or two.
For an initial test, I hooked it up to the famous—in my mind, at least—WB3GCK Downspout Antenna. The little Z-match loaded up the downspout on 40 through 10 meters with no problems. On most bands, I could get the LED indicator to go completely out. On one or two bands, I couldn’t get it completely extinguished but it did give a definite null. Double-checking with a second SWR bridge indicated that the SWR was 1.5:1 or less in this condition. While tuned up on 40 meters, I had a quick QSO with a station near Chicago from here in southeastern Pennsylvania with 3 watts.
This little Z-Match tuner was one of my favorite—and most useful—projects. It’s a great accessory for QRP rigs that lack an internal tuner or SWR meter.
Here’s an example of what can happen when you have a hunk of cheap wire and a little too much time on your hands.
Years back, I did a write-up on a simple, random wire antenna made from a 50-foot roll of speaker wire from a local dollar store. I nick-named it the Dollar Store Special. I had a similar roll of wire in my junk box, so I set out to see if I could build another useful portable antenna from it.
This time out, I wanted to build something more elaborate than a random wire. After some sketching with a pencil and paper, I came up with this simple portable delta loop.
There are certainly better ways to construct a delta loop. However, I just wanted to see if I could build a functional antenna using only cheap speaker wire. So, with that in mind, here’s how I did it.
The antenna I built was inspired by a portable delta loop designed by Doug DeMaw, W1FB.  Doug’s multiband delta loop was designed for the 40M band and used a 300-ohm balanced feeder.
According to Doug’s book, this type of antenna should work well on the fundamental frequency and higher. For the next band below the fundamental, he suggests connecting the feeder wires together and using it like a random wire. I figured I’d just try loading it up as is to see what happens.
Given that I constrained myself to a 50-foot roll of speak wire, I scaled my antenna for the 20M band. Using the formula, 1005 divided by the frequency in megahertz, I calculated a total length of 71 feet (21.6 meters) for the center of the 20M band. That would leave some of the two-conductor wire for an improvised balanced feeder.
Feeding the delta loop in a corner (with the apex of the loop pointing up), gives the antenna vertical polarity with a low take-off angle. As with most antennas, higher is better. However, this antenna is still quite useful at practical heights in the field.
Since a tuner will always be necessary, I expended no effort trying to optimize the design.
If you’re a visual person like me, refer to the diagram to help make sense of the directions below.
Measure off 35.5 feet from one end of the speaker wire. Place a small zip-tie around the wire at this point.
Separate the 35.5-foot end of the speaker wire into two separate wires.
Strip and solder the loose ends of the 35.5-foot wires together. Put some electrical tape or shrink tubing over the splice.
Make 3 small loops in the wire, as shown in the diagram. You can see an example in the accompanying photo. These are going to be the attachment points. I used some Goop® adhesive on the zip-ties to help hold things in place.
Finally, install some spade terminals on the ends of the shorter conductors. These will be used to attach the antenna to your tuner or balun.
For my initial tests, I used a 28-foot Jackite pole to support the antenna. I only partially-extended the pole, such that the bottom of the antenna was about 4 to 5 feet off the ground. I used some nylon twine and a couple of tent stakes to tie off the two bottom corners.
The setup was somewhat more complicated than most portable antennas I use. It took me about 20 minutes to get it set up, but I suppose that wasn’t too bad for my first time.
I used a couple of large tent stakes to keep the feedline off the ground. I connected the antenna to my KX3 using a 4:1 balun and a 1-foot piece of coax.
I first did a quick check to see what bands the KX3’s internal antenna tuner would handle. I found that I could load it up on every band from 60M through 6M, although I couldn’t get the SWR below 2:1 in the low end of 40M. That’s not surprising for a 20M loop, I suppose. I did have a usuable match between 7.030 and 7.060, where I normally operate.
I was only about 50 yards away from some powerlines, but the loop seemed quiet on receive.
On 20M, a French station answered my third CQ. I also made contacts with Missouri and wrapped up with yet another French station.
From the signal report the last station gave me, this antenna appears to do reasonably well with DX on 20M running QRP. It was a chilly and windy day, so I didn’t stay out there to try for contacts on other bands.
Although my initial outing with this antenna was promising, I need to spend some more time using it on bands other than 20M. In any event, it was a fun—and cheap—antenna project.
73, Craig WB3GCK
 DeMaw, D. (1991). Technical Bits & Pieces. In W1FB’s QRP Notebook (2nd Edition, pp. 157–161). Newington, CT: QST.  DeMaw, D., & Aurick, L. (1984, October). The Full-Wave Delta Loop at Low Height. QST, 24–26.
In a recent post, I covered some (very) basic information about the venerable doublet antenna. This time around, I’ll cover some practical examples. These are antennas I have used and one unique design I know of.
Doublet Fed with TV Twinlead
My go-to portable antenna for several years was a simple doublet fed with 25 feet of that cheap, brown TV twin-lead. For the radiating elements, I used some #22 stranded hookup wire.
I first built the antenna as a 40M dipole fed with RG-174 coax. After a while, I wanted to cover multiple bands, so I removed the coax and replaced it with the twin-lead. I used a small piece of fiberglass perf board for the center insulator.
I have often used my homebrew Z-match tuner to load it up, although a 4:1 balun and a short run of coax to my rig’s internal tuner works fine, too. The whole antenna weighs next to nothing, and fits in a sandwich-sized Ziplock® bag.
Nothing fancy but it works great.
Up and Outer
The Up and Outer is simply a doublet with one vertical leg and one horizontal leg. I had done some experimenting with this old-time antenna and decided to build one to use while on vacation in the Outer Banks of North Carolina.
I planned to support the vertical leg with a 28-foot Jackite pole, so I made a simple modification to a 44-foot doublet I had on the shelf. I spliced 6 feet of additional wire to each of the elements down to 28 feet each, and I was in business. Like my 40M doublet, the Up and Outer is fed with TV twin-lead and uses a perf board center insulator.
This antenna always goes with me on our annual Outer Banks vacation. I’ve used it from numerous beach rental houses, and it’s perfect for use on a second story deck. I used it last summer with great results, connecting it directly to my KX3. And, if I need to, I can use it as a normal horizontal doublet.
Appalachian Trail (AT) Dipole
This design is the brainchild of my friend, Ed Breneiser WA3WSJ, and goes back about 20 years. Rich Arland K7SZ, wrote about it in his QRP column in QST  back in 2001 and devoted a few pages to it in one of his books .
In simplest terms, it’s a 40M doublet made from #26 copper-clad stealth wire. Ed used a 3/4-inch PVC end cap for the center insulator (see photo). After soldering wires to an SO-239 socket and routing the wires through the end cap, the inside of the end cap is potted with epoxy. This makes it pretty much bomb-proof.
The antenna is fed with 300-ohm ladder line, which is soldered to a PL-259 UHF connector. The PL-259 probably causes a slight imbalance, but in the field, you’ll never notice it. You can also feed it with coax and use it as a normal 40M dipole. Pretty cool, huh?
When I built mine, I went with some #22 stranded hookup wire I had on hand. Although I departed from Ed’s design a bit, this doublet has been a reliable portable antenna over the years.
WV0H Park Doublet
Myron WV0H designed a unique doublet that he dubbed The WVØH Park Portable Doublet. He uses two 50-foot pieces of wire to create a 60-foot doublet fed with a built-in open-wire feeder. I won’t attempt to offer a detailed description here; Myron’s blog post provides all the details you need to build one. Go check it out.
While I’ve never used Myron’s unique antenna, I can vouch that it works. I worked Myron a few years back while he was out in a park with his doublet. I can attest that it puts out a great QRP signal.
Well, that’s about it. If you need a reliable, easy-to-build, multi-band antenna, give the time-tested doublet a try.
73, Craig WB3GCK
References:  Arland, R. (2001, July). QRP Power – Antenna Time. QST, p. 100.  Arland, Richard K7SZ, Low Power Communication – The Art and Science of QRP, The American Radio Relay League, 2nd Edition, 2004, Chapter 6, pp. 6-36, 6-37
I was recently going through my stash of portable wire antennas and came across one of my old favorites—the doublet. I don’t see too many references to this type of antenna these days, but the doublet provides a great portable antenna option.
What is it?
The doublet, simply put, is just a dipole. The difference is that you feed it with a balanced feeder, rather than coax.
Hams have been using doublets for many years. The earliest reference I could find in the ARRL QST archives was from September of 1929. In this write-up, Clair Foster W6HM describes a 40M doublet fed with twisted wire lamp cord used for receiving.
Advantages of the Doublet
The balanced feeder provides some advantages. Depending on how it’s constructed, it can withstand higher SWR with lower losses than coax. Because of the low losses at high SWR, you can use the doublet as a multi-band antenna.
As a portable antenna, it’s hard to beat, especially as an inverted vee. Use a tree branch or telescopic pole to hoist up the center, tie off the ends, and you’re in business. 
This multi-band capability comes with some disadvantages, though. Fortunately, none of them are insurmountable.
First, you’ll need a transmatch that can handle balanced feedlines. Typical commercially-available feedlines have either 300 or 450-ohm characteristic impedances. For open-wire feedlines, the impedance can sometimes be 600 ohms or more.
You can also use a balun to transition from the balanced feedline to 50-ohm coax. While this isn’t an optimum approach, it works. Textbooks often recommend a 4:1 balun, and that’s a good starting point. If you go this route, I recommend keeping the coax as short as practical. If you run into matching problems on some bands, try another balun ratio (e.g., 1:1), or change the length of your feedline.
The second drawback is that you need to be careful of how you route balanced lines. You need to avoid getting it too close to metal or laying it on the ground. Both can upset the line’s balance. This can cause it to radiate or introduce losses. If you have excess line, don’t coil it up. Operating outdoors, I found these restrictions aren’t very difficult to work around; you just need to be mindful of them.
Building the doublet is pretty simple. Many folks suggest making the doublet a half-wavelength long at the lowest band you intend to use. I’ve built one for 40M and it worked well on 40M and higher. Depending on your tuner, it may also be usable on the next lower band.
L. B. Cebik W4RNL (SK) popularized the 44-foot doublet for 40M-10M. According to Cebik’s analysis, this length produces a more consistent radiation pattern across the bands.
Regardless of the size of the doublet, you should try to avoid certain feedline lengths. One rule-of-thumb suggests avoiding combinations of feedline electrical length plus one leg of the radiator that are odd multiples of an eighth-wavelength.  If you run into matching problems, you can try adjusting the length of either the feedline or the radiating elements.
You have several options here:
Commercial 450-ohm or 300-ohm ladder line. These are commonly available, and they work great.
Homebrew open-wire feeders. This is the most efficient option. If you do some Internet searching, you’re likely to find lots of ways to build open-wire feeders. SOTABEAMS has a great example on their website.
TV twin-lead. I’ve used the cheap, brown stuff quite a bit for portable doublets. Unfortunately, it’s nearly impossible to find these days. If you come across it somewhere, stock up!
Lamp cord or speaker wire. This works and I’ve seen folks use it for portable antennas. However, it can be lossy, compared to window line or open-wire feeders.
If you want more technical details on this antenna, information abounds on the Internet and in antenna books. In particular, Cebik wrote some great articles that are worth searching for.
In a future post, I’ll cover some practical examples that I have come across or used in the field.
73, Craig WB3GCK
References:  Foster, C. W6HM (1929, September). Experimenters’ Corner: The “Doublet” for Receiving. QST, p. 39.  DeMaw, D. W1FB (1991). Technical Bits & Pieces. In W1FB’s QRP Notebook (2nd Ed., pp. 157–161). Newington, CT: QST.  Heys, John D., G3BDQ (1989). Center-fed antennas using tuned feedlines. In Practical Wire Antennas. Bedford, UK: Radio Society of Great Britain, p 7.
[NOTE: This is an updated version of an old article from my QSL.NET website. In the interest of full disclosure: My local dollar store no longer sells the speaker wire I used. While it’ll probably cost you a few more bucks to build one, it’ll still be a cheap antenna. Although the original article has been on my website for 15 years, I still get the occasional email from folks who have built one.]
I love rummaging through our local dollar store. One of the biggest bargains in our local dollar store is speaker wire. You can get 50 feet of two-conductor speaker wire for a buck. Not too shabby. I always keep a bunch of the stuff on hand for antenna experimentation.
Using a single 50-foot roll of dollar store speaker wire, I made a simple 50-foot random wire antenna with counterpoise wires to cover the 40, 30 and 20-meter bands. I stashed the whole kit in a zip-lock sandwich bag and always keep it on hand as a backup antenna system whenever I operate in the field. With a simple antenna tuner of some sort, this will get you on the air in a pinch, should your primary antenna fail.
Here’s all you have to do:
Separate the conductors so that you now have two separate 50-foot wires.
For the radiator, take one of the 50-foot wires and crimp a small ring lug to one end—right over the insulation. This gives you someplace to tie a line to hoist it up. On the other end, just strip off a half-inch or so of the insulation. You can leave it bare or add whatever kind of connector you want; whatever works best with your tuner.
For the counterpoise wires, take the remaining 50-foot wire and cut it so that you have a 33-foot wire and a 17-foot wire. If you only want to work 40 and 20 meters, you can stop right here. You now have counterpoise wires for both of these bands.
To provide a counterpoise wire for 30 meters, take the 33-foot wire from Step #3 and cut it so that you now have a 23-foot wire and a 10-foot wire. Strip off about 1/2-inch of insulation from one end of the 23-foot wire. Install a quick-disconnect connector of some sort on the other end, so that you can join the 23-foot and 10-foot wire sections together. The idea here is that, with the two wires connected, you have a 33-foot counterpoise wire for 40 meters. With the two sections separated, you now have a 23-foot counterpoise wire for 30 meters.
[Note: If you only plan to operate with the radials laying on the ground, cutting them to resonance isn’t too important. You can simplify things a bit by going with just the 33 and 16-foot wires. I think two 25-foot wires would be sufficient, as well. Three 16.6-ft radials is another option to consider. Feel free to experiment here and see what works for you.]
In operation, just hoist one end of the 50-foot radiator up in a tree or other suitable support. Connect the other end to the hot side of your tuner. Connect the 33-foot and 17-foot counterpoise wires to the ground connection on your tuner and lay them out on the ground. When you want to work 30 meters, just disconnect the quick-disconnect on the longer counterpoise wire. Pretty simple, eh? Any type of simple L-tuner should work fine for this.
Please note that I wouldn’t recommend using this wire for a permanent outdoor antenna. It’s not suited for that kind of use. But for temporary outdoor use, it’ll do just fine. Besides, if the wire goes bad, you can always replace the whole thing for a dollar!
Here’s yet another quick little hack. I raided my junk box to cobble together a ground mount for my portable vertical. While this solved a couple of specific issues I had, it might only be of interest to a few of you folks out there.
I often support my 19-foot vertical with one of those inexpensive fishing poles from eBay. (I paid around $10 USD for my 7.2M pole.) I had been using a simple method for ground mounting. I shove a screwdriver in the ground, take the bottom cap off of the pole, and place the pole over the screwdriver. Voila!
While the screwdriver technique is a useful way to support my vertical, there are two issues with it. First, the screwdriver method places the bottom of the pole in direct contact with the dirt. This can gunk up the threads on the bottom of the pole. (Ask me how I know.) Next, since my homebrew 19-foot vertical takes up the entire length of the pole, the matchbox ends up too close to the ground for my liking. I made a simple little gizmo that addresses both of these issues.
From some scraps and junk I had on hand, I used the following:
Duct tape (optional, for a better fit between the 1/2-inch PVC and the bottom of the pole)
A dab of Lock-Tite thread locker
[Note: The PVC pipe I used works with the particular pole I use. If the bottom of your pole has a different inside diameter, you might need to use a different size pipe.]
I joined the two pieces of PVC pipe together with the PVC reducer. Then I glued the two end caps together, back-to-back. Next, I drilled a 1/4-inch hole through the center of the two end caps. I fastened the stainless steel rod with two nuts and a lock washer. I also used a dab of thread locker for good measure. I had to do some sanding on the 3/4-inch pipe to allow the end caps to slide on and off easier. At this point, you might want to put a layer or two of duct tape on the 1/2-inch pipe for a snug fit inside the pole.
In the field, I place the end cap assembly on the 3/4-inch pipe and shove the rod into the ground. The pole goes over the 1/2-inch PVC pipe, of course. This places the bottom of the pole about 8 inches above the ground. With lightweight poles, guying is unnecessary. For travel, I flip the end cap assembly around so that the bolt stores inside the pipe. This prevents poking holes in my backpack or bicycle pannier bags.
The threads on the end of the stainless steel rod pick up some dirt in use. It’s not a major problem but I might cut the rod off just above the threads. I haven’t decided yet.
That’s all there is to it. I’m hoping the accompanying pictures clarify how I built it.
This is another one of those little hacks that takes longer to describe than to build. Some time ago, I stumbled on a clever idea online that has been useful in my ham radio activities.
I used to use ball bungee fasteners in a variety of sizes as temporary fasteners. While they are handy, they have limitations for my uses. On occasion, I found that the sizes I had available were either too small or too large for the task at hand.
A year or two back, I found a great video on the MOD YouTube Channel. The video described how to make these simple, adjustable cable ties. I made up a few and found them handy for several ham-related applications.
These little devices have a multitude of uses but my main use is for antennas in the field. I use them to fasten a BALUN or UNUN to a telescopic pole for portable verticals.
I also found they are also handy for lashing odd items to the MOLLE loops on my backpack. In a recent post, I showed how I use them to secure a 19-foot telescopic pole to my sling pack.
Of course, they make great cable ties. Their ability to adjust allows them to fit a wide variety of cables.
I use 4mm diameter shock cord most often to make these. For some smaller, light-duty applications, I have used a thinner 2.5mm shock cord. I have found that the cord locks seem to hold better with the larger 4mm shock cord.
Construction is super simple.
Cut the shock cord to the desired length. Be sure to singe the cut ends with a lighter to prevent fraying.
Put the two ends through the holes in the cord lock.
Holding the two ends together, tie a simple overhand knot and snug it down.
To use them, place the bungee around whatever you need to fasten. Place the loop end over the cord lock to hold it. Press the button on the cord lock and pull the ends to cinch it down.
That’s all there is to it. In the time it took to write and edit this post, I could have made a ton of these things. It’s not an Earth-shattering thing but sometimes it doesn’t take much to amuse me.