antennas

This follows the EFHW Fail article. There are a lot of ways to configure an End Fed Half Wave antenna. The earlier article explored a variant that sort of works, but not as well as expected … and certainly not as well as this one.

This EFHW variant is very common, a 49:1 transformer, bridged with a 100pf capacitor, and about 67 feet of wire. It is designed for 40M and higher. Once assembled, the wire is cut to a length that produces the desired resonance points, and there are several with this design.

About design… There’s a well known chart for Random Wire Antenna Lengths. It shows all sorts of lengths to use for antennas that are (1) random length, (2) are not resident on any band, and (3) always require the use of an antenna tuner. There must be some good rationale for such a thing, but it befuddles me why anyone intentionally always wants to use part of their RF output to warm up coils in a tuner. Aren’t antennas resonant at the desired frequencies a lot more efficient? OK, let’s set that aside… the chart is also, maybe unintentionally, helpful for offering the good lengths for EFHW antennas that have multiple natural resonance points. Just use the parts of the chart marked in red that the chart labels “Lengths to avoid.” They are EXACTLY the ones we want.

That blue oval is my addition to the chart, and the starting point for this antenna’s length. The actual length, trimmed as I like it, is 66 feet, 5 inches.

The design is so popular that a number of hams sell kits for building a 40m version. These are the people willing to gather all the parts, package them nicely for us, and save us the effort of finding each individual piece. Just try buying one BNC connector and paying shipping for it, then the wire, then the capacitor, then the torroid, etc. etc. One of those kit packagers is Jason Oleham, KM4ACK. His kit sells for about $40 and is often out of stock because of its popularity. The KM4ACK EFHW kit was the starting point for my EFHW adventures. It worked better than many other wire antennas I experimented with over the past year. As advertised, it is naturally resonant on 40M, 20M, 15M and 10M. With careful trimming, I made mine happy to work very well in the CW portions of those bands. BTW, it works with NO counterpoise, and is not sensitive to feedline length.

Below are NanoVNA screenshots for 3-20Mhz, 40M, 20M, 15M and 10M. In all the charts, the marker shows the QRP hailing frequency in the CW portion of the band.

Interestingly, the tuner built into the Penntek TR-45L can tune this antenna on 80M and 30M, but definitely not on 17M. I haven’t actually made contacts with the tuned results on 80M and 30M, but have on the other bands. I’m very pleased with the results, a good step toward frequency resilience for this HOA ham. Next, let’s see what it does when placed under roof.

Under roof update: My original idea was to use this successful antenna as an indoors antenna, in the attic space of our home. That didn’t work out so well. Due to a local prohibition against wandering around in the attic, I hired a wiring firm to do the job. With little antenna experience they installed it, but not as high as I wanted, and “folded” into a tortuous path. It’s a failure in any but the last-chance alternative.

Next, let’s look at a couple of WSPR runs for the bands I use most, 20M and 40M. I’ll get to WSPR runs for the other bands soon. In the meantime, I’ll mention that my first contacts on 15M and 10M with this antenna were TX and AZ.

Living in an HOA area, my constant quest is for a stealthy, multiband, effective antenna. When I arrive at a good one, I plan to install it in the attic. That installation will reduce the everyday setup and teardown of the “backyard” portable antennas. Over the past year, I’ve tried many antennas and my antenna junk box is full of “spare parts.” I added more to the pile yesterday. It actually is a workable antenna, but one that fails to be as good as others, and fails to meet my expectations.

The antenna is an EFHW that I found in an issue of CQ magazine from several years ago. I won’t be more specific, because I don’t want to cast blame. The thing might work very well for someone else. Like all EFHW designs, this one is a transformer and a wire. The transformer is 36:1, the wire about 65 feet (later cut to trim for 20M), and has an RC network about 1/3 of the way along the length.

My test rig for such an antenna is putting it up in an inverted vee form using a 17 foot collapsible mast as the center support. That form sort of mimics the roofline of the house, for when I move it into the attic. Measurements are made with a NanoVNA.

There’s another EFHW that does better. We’ll see it shortly…

It is common knowledge that a dipole antenna, at sufficient height, is an efficient antenna.

I’ve been exploring a dipole as an option for a permanent antenna. My explorations are currently constrained by two factors. First, I have no outside supports, poles, trees, etc. for hanging a dipole, nor will they fit within the HOA restrictions. Second, I have not yet decided to place anything in the attic space. Many advise that the space is difficult to navigate, mostly because of air-conditioning / heating ducts.

My first proof of concept idea was to hang a dipole inside the lanai (screened in back patio). A half-wave dipole fits in that space by wrapping about 1.5 feet around at each end. I made a simple dipole of speaker wire and positioned it at the top of the lanai, about 10 feet above ground. As with all my antenna experiments, I cut it to optimal length for resonance at 14.060 Mhz.

My first paragraph mentioned “at sufficient height.” We’re not there yet. I can gain more height by putting it inside the attic as an inverted vee. …sometime in the future…

My earlier Ham life, way back in the 70s, was in an area with no antenna restrictions and I never gave them much thought.

I set the hobby aside long ago for career and family reasons. Eventually retirement happened and we moved from snow country to sun country. A year or so after moving to The Villages in Florida in 2020 the ham bug bit hard and I became aware of the area’s antenna restrictions. They basically say “no antennas of any type.” It is very understandable that large or grotesque antenna structures are out of place in most neighborhoods and can be detrimental to property values. I agree whole heartedly.

Good neighbors

The general consensus of the several hundred hams in The Villages, and their many neighbors, is “out of sight” is generally acceptable, especially “can’t see it from the street.” As I re-started this hobby, I set up a “backyard portable” vertical (Wolf River Coils 17′) I also talked with the closest neighbors about the ham radio hobby and what I was doing. Both thought it interesting and had no objections. One even offered to help. (Thanks Jim!)

For the time being, I’m using “backyard portable” as a way to experiment in search of effective antennas. One might be a candidate for a full time, permanent installation, suitably hidden. The good news is that I’m discovering what works and what doesn’t (and collecting lots of parts from failed experiments). The bad news is needing to set up and tear down every day. I take everything down near nightfall because there are critters in that marsh behind us that will carry anything away that’s not permanently nailed down. That’s OK for POTA, a daytime activity, but I’m missing the opportunity to work all the night owl hams. Tryin’ to fix that … working now to find someone able to crawl the attic and tack up an EFHW wire that has proven worthwhile. (Update: see Noise in the attic?)

A variety of solutions

The Villages Amateur Radio Club, TVARC, has several hundred members, many of which are very active. A recent meeting offered a presentation by 11 members on how they deal with the antenna restrictions. They published the presentation as a PDF here. Beware: it is a sizeable download, 51MB, 92 pages. Prominent among the solutions were flag poles; a bit more on those shortly. Other solutions included nearly invisible wires, attic installations, rain gutters and others.

Flagpoles

There is a provision in the published covenant which says, “The Location of any approved device will be as previously approved by the Developer in writing.” The single “approved device” in The Villages is a flagpole … as long as it is no taller than 22 feet and doesn’t look like an antenna. The real origin of this solution is in a Florida Statute, Chapter 702 Section 304. That law describes the right to display flags. It says nothing of antennas within flagpoles or flagpoles themselves being used as antennas, but does say that HOAs shall not prohibit flagpoles or the display of flags. Read it yourself: Florida Statute, Chapter 702 Section 304

A lot of hams have flagpole antennas. There are several interesting variants. One variant uses a PVC pipe that is large enough in diameter to contain a multi-band vertical, often the popular Hustler 6BTV. Another variant uses a split metal pipe flagpole with a base pipe firmly fixed in the ground but extending only a few feet. Above the ground the metal pipe is electrically separated from base by a PVC core, and the upper part is tuned to the desired band by very broadband tuners. A third variation, that I saw just recently, uses the pole to support one or more nearly invisible external vertical wires similar to the DX Commander. Yet another uses the pole to support very lightweight, barely visible, wires running off in useful directions and lengths. It seems that many flagpole installations, especially the ones that use the metal pole as a radiating element, use remote tuners (hidden in the shrubbery), and I’m guessing that most who use that type of antenna are also running 100 watts or more. I’m not there yet. The obvious place for a flagpole on our property is already occupied, and I’m not at all enthusiastic about needing either high power or a tuner.

I’m not yet ready to install anything permanent in the backyard, or push the boundaries on size and types of structure. In fact, I’m spending a lot of time experimenting and working toward a goal of having a virtually invisible antenna farm available 24/7. My challenge is how to fit HF antennas in small spaces, and how to create efficient antennas that work well within QRP power, 5 watts. Thus, the focus of most articles on this site.

The Shark HamStick monoband antennas perform fairly well for me. Like all of my “backyard field day” antennas, the downside is that I need to set them up in the morning and bring them in at night. There’s all sorts of wildlife in that wetland behind us and I don’t need a gator or wild pig dragging away my stuff. Although it takes only a few minutes, how about something more permanent?

Idea! One of the hams around here uses a couple of tarheel screwdrivers attached to the structure at the back of his home. That structure has a large metal framework that he uses as a ground plane for the antennas. I don’t have that same sort of structure, but I do have a full surround of rain gutters and the downspouts run into the ground. Hmmmm, wouldn’t they be a good ground plane?

Nope, nada, no way José! As a feasibility test, I took a HamStick up to the gutter, using a WRC base mount, clamped it in place, set a grounding wire from the base to the gutter structure, and tuned it a bit. The best I could get was an SWR of 2.3:1. The tuner in the TR-45L is definitely not happy with that … and the grounded rain gutters are certainly not a ground plane.

Why HamSticks when I already have a perfectly useful Wolf River Coils antenna? Simple: frequency resiliency. When I want to change bands with the WRC, it’s a matter of getting out the NanoVNA and adjusting the coil, and usually adjusting whip length. I like to run as much as possible with NO TUNER. The TR-45L has a tuner that works well, but I’d rather use my meager RF to heat the antenna instead of the tuner. So, I tune the antennas. It’s a procedure that usually takes a few minutes to get right. Instead, a quick change of HamSticks (each already tuned for its band) is substantially faster.

Update – best configuration

There are as many ways to configure HamSticks as there are imaginative hams. While originally intended for vehicles, we see HamSticks in many uses other than mobile.

The configuration shown above has things stacked up from the ground in this order:

• buried radial field
• Wolf River Coils aluminum tripod, clipped to the radials via a banana plug
• Two 24 inch aluminum extensions (again, WRC parts)
• The Shark 20M HamStick with the “stinger” tuned for the best SWR at 14.06 Mhz

Now, what if I removed one of those extensions? Can I get a better SWR? Yes, definitely!

• The version with 2 extensions, stinger length 18 1/2 inches, has an SWR of 1.411 with 34.76-J1.12Ω impedance.
• The version with 1 extension, stinger length 22 3/4 inches, has an SWR of 1.087 with 54.15-J1.25Ω impedance, clearly BETTER, and the transceiver is happier too. …BEST…

Of course, the next question is, what about no extensions … with the HamStick directly on the tripod?

• The version with no extensions, stinger length 26 9/16 inches, has an SWR of 1.24 with 61.1+J5.0Ω impedance, better than the 2 extension version, but not the best.

UPDATE – May 6 2024 – I’ve been running the 20M HamStick for some time directly atop the WRC tripod attached to the radial field. The NanoVNA consistently reports that configuration as having 1.02 to 1.04 SWR. BEST YET!