Many thanks to Steve (KM4FLF/VA3FLF) for sharing the following guest post:
A Great Homebrew Vertical Antenna
by Steve (KM4FLF/VA3FLF)
Last spring, I was going through my many boxes of ham “stuff” looking for items to sell at our club tail gate sale. I came across a couple of Hustler SM Series Resonators (20 /40 Meters) that I had acquired. I am not sure where I obtained them, but I decided they were keepers. That decision turned out to be the first step in a year long process that has given me an awesome homebrew vertical antenna.
After doing a little research I found the resonators and accessories at most of the online ham dealers. They are used primarily as mobile and marine antennas. I had seen where a ham had used these on a ground stake as a portable antenna as well. I ordered a Hustler MO1 mast which is 54 inches tall and thought I would attempt to make a portable POTA antenna.
I had a couple of small aluminum plates that I drilled out a few holes. I cut out a notch to put a SO-239 Stud Mount on the plate as my antenna base. I now had a ground plate, connector, and antenna with resonator. By putting a stake in the bottom of the plate, I was able to get the antenna to stand up. The Hustler resonators have a hex screw for tuning that can be loosened. The antenna can be adjusted for resonance by lengthening or shortening the radiator length. After adjusting the radiator my SWR was still horrible on the two bands.
I had some 14-gauge wire laying around and attached it to the plate using carriage bolts and nuts for my ground radials. I didn’t think about the length of the wires at this point but went with three or four lines around 20 to 30 ft. I was able to use my vertical a few times with moderate success. My SWR on 20 and 40 Meters was around 2:0 to 1 at best. It was bulky and very delicate. Sometimes screwing in or unscrewing the MO1 the SO239 would slide off the edge of the aluminum plate. I put away my contraption for the winter and decided to move on to something else.
I discovered something you might have an interest in for your wire antenna deployment. Years ago when I was a building contractor, we used chalk line for floor layout. It has a very high tensile strength and is very light weight. After reflecting on this, I recently bought a 100’ spool of braided 1 millimeter chalk line and used it for a field deployment. I attached my “throw weight” to it and easily launched it about 60’ into a tree. You can see it in the attached photo holding my homebrew EFHW to my Jeep.
The magnet wire was scavenged from a HUGE transformer from a neighbor’s discarded light fixture.
I did the new installation for him and he gave me the old one. I promptly disassembled it and collected miles of 14 and 20 gauge magnet wire 😊!
I haven’t added the capacitor to this antenna yet because it is sufficiently resonant and broadbanded on 40, 20, 15, and 10 Meters. I did some testing with the capacitors though on my previous build which was the PVC tube EFHW transformer. I believe I may have sent you a photo of that in a previous message. It too was resonant in the same places, but adding the capacitor smoothed and widened the acceptable SWR range.
The attached photos are my complete antenna assembly: matching transformer (49:1), 65.5’ speaker wire, 100’ braided 1MM chalk line, and throw weight (epoxy filled lug nut with short paracord pigtail).
Compact and lightweight.
I love this, Dan! I also like how self-contained and compact it is. What a professional job, too, with heat shrink, proper connection points and tie-offs.
Do you have an antenna or radio project you’d like to share on QRPer.com? Contact me!
Until 2016, I had never purchased a commercial field antenna; I built all the ones I had ever used.
These days, I take a number of commercial antennas to the field and use them in my real-time videos and I really enjoy deploying and using them. My buddy Eric (WD8RIF) reminded me, though, that I hadn’t actually used a homebrew antenna in ages. He was right!
You see, while I believe commercial field antennas can be incredibly durable and compact, it’s important to note that antennas are one of the easiest components of an amateur radio system to build yourself. They require only the most simple of tools and are very affordable. And the best part? They can perform as well as those that are available commercially.
I also get a great deal of pleasure out of building things.
A simple goal
I’ve mentioned in previous posts that I often set a little goal that runs in the back of my mind for each park or summit activation I make.
On Monday, June 14, 2021, I made a simple goal: buy my antenna wire en route to Lake James State Park, build the antenna on site, and complete a valid Parks On The Air (POTA) activation.
A very simple antenna
I also decided to employ my Xiegu X5105 since 1.) it’s one of the most affordable general coverage QRP transceivers I own and 2.) it has a built-in antenna tuner (ATU).
One of the cool things about having an ATU is that, if it has the matching range, you can allow it to do the “heavy lifting” in terms of matching impedance.
Although I’d never put the X5105 to the test, I suspected its internal ATU would have the matching range to forgo building a 4:1 or 9:1 transformer and simply pair it directly with a random wire.
All I would need was a 28.5 foot length of wire for a radiator, at least a 17 foot length for a counterpoise, and a BNC to binding post adapter.
The antenna would benefit from multiple 17′ counterpoises, but I really wanted to keep this setup dead simple to prove that anyone can build an effective field antenna with a very minimum amount of components.
Even though I have plenty of wire lying around the house to build this simple antenna, I wanted to pretend I had none to prove that any wire would work.
And to add just a wee bit more challenge, I also limited myself to shopping for antenna wire between my home and the park without making a serious detour from my route. That really limited my options because there isn’t much in terms of commercial areas between me and Lake James State Park.
As I left the QTH, I decided that the best spot to shop was a Walmart in Marion, NC. It would only be a four minute round-trip detour at most. I had a hunch that Walmart would even have speaker wire which would be ideal for this application.
In my head, I imagined I would have at least three or four choices in speaker wire (various gauges and lengths), but turns out I had a difficult time finding some at Walmart. We live in such a Bluetooth world, I suppose there isn’t much demand for it these days. A store associate helped me find the only speaker wire they had which was basically a 100 foot roll of the “premium” stuff for $17 US.
While I would like to have paid a fraction of that, in the end it’s not a bad price because once you separate the two conductors, you have double the amount of wire: 200 feet.
Although the frugal guy in me cringed, I bit the bullet and purchased their speaker wire. To be clear, though, I could have found another source of wire in that Walmart, but I preferred speaker wire for this application. And $17 to (hopefully!) prove a point? That’s a deal! 🙂
Lake James State Park (K-2739)
Once I arrived on site, I found a picnic site I’d used before with some tall trees around it.
Here’s how I prepared the antenna:
First, I cut 28.5 feet of the speaker wire from the roll and split the paired wires so that I’d have two full 28.5 foot lengths.
Next, I stripped the ends of the wire and attached banana jacks I found in my junk drawer. Although these aren’t necessary as the binding post adapter can pair directly with the wire, I though it might make for a cleaner install. In the end, though, I wasn’t pleased with the connection to the radiator, so dispensed with one of the banana jacks on site, and later dispensed with the other one as well. The connection is actually stronger without the banana jacks.
I then deployed the 28.5 radiator with my arborist throw line, and laid the other 28.5 half on the ground (the ground of this antenna would pair with the black binding post, the radiator with the red post). I only needed 17 feet of counterpoise, but once it couples with the ground, I don’t think any extra length makes a difference (although less than 17 feet likely would).
The antenna was essentially set up as a vertical random wire with one counterpoise.
I then plugged the BNC binding post adapter into the rig, hit the ATU button, and was on the air.
All I can say is that I’m incredibly impressed with the X5105 internal battery. This was my fourth activation from one initial charge on May 16. The battery lasted for 20 minutes, taking me well beyond the 10 contacts needed to validate this park. I’ll now consider taking the X5105 on a multiple SOTA summit run!
Even thought the heat was intense and the humidity even more intense, I decided to take in a 2 mile hike post-activation. I snapped a few shots along the way.
I’ll plan to add more counterpoises to the speaker wire antenna as I know this will only help efficiency.
In addition, I’ll plan to build even more antennas with this roll of speaker wire. If you have some suggestions, feel free to comment!