Archive for the ‘antennas’ Category

My You Can Think of the Darndest Things While in a Hospital Bed…

Listeners to the ICQ Podcast where I appear monthly as a Presenter probably heard me say that I was successfully treated for a highly aggressive prostate cancer (adenocarcinoma, Gleason 8) almost two years ago at the Mayo Clinic. While in Rochester for two weeks, I had a lot of time in bed recovering from the surgery before being released for home back in Mississippi. For me, I tried to keep my mind on things besides the cancer treatment as I had the top prostate cancer hospital in the U.S. treating me and the top robotic surgeon, Dr. Igor Frank, at the helm. So what does a ham think about in this circumstance? Let me tell you…

Antennas! I worked out plans for a half dozen portable antenna designs that had been smoldering in my brain before the unexpected diagnosis and biopsy. Don Field, Editor of Practical Wireless, expressed an interest in first dibs on each manuscript resulting from my experiments with portable HF antennas. Here are a few that are published or in-press as of this writing. And more to come.

Eiffeltenna

Based on the almost whimsical Youtube video by Jim Heath W6LG (now sk), I considered the photography lighting tripod, ubiquitous in the camera industry. Jim put together a quick-and-dirty (unusual for him) vertical antenna based on a type of tripod construction that electrically isolates the three legs from the telescoping vertical part. Brilliant! They are inexpensive so I bought a few from Amazon or eBay to experiment with. I paired the tripod with a 17′ telescoping whip and an inductor coil, finishing off the “fine French dining” concept with a tablecloth underneath of Faraday Cloth. Following my focus on making each section having a low resistance electrical connection when extended, it works very well. Very quick to set up, take down, and pack. It appeared in the October 2025 issue of PW. Bon appetit!

Delta Vee AutoLoop

Loop antennas of all designs have fascinated me since I was a teen building classic ones for AM BCB DXing. I have a sort-of horizontal loop around the edges of my roof due to HOA restrictions. )I have also written about that in PW-see March 2023 issue.) When Chameleon released their Tactical Delta Loop, I took a look at my friend, Steve KM9G’s take on it (see Temporarily Offline on Youtube). He found it was very flat across most HF bands. Hmm. Lawrence Cebik’s earlier models of loops, including the Delta geometry, showed that it has harmonics based on the design band and that height above ground places a significant part in the feedpoint impedance. What antenna magic have the Chameleon engineers come up with? Whatever it was, it priced out at over $400 USD.

From watching TO’s channel and the brief review of Michael KB9VBR, it appears that they use a fixed 5:1 balun to get the impedance down to the 50 ohm ballpark. I don’t understand TO’s flat SWR but antennas nearly on the ground can do funny things. So my take on the problem here was we can choose to optimize the balun wind for a certain band with some higher band harmonics working against a tuner for a reasonable match or just have a single band antenna. But wait. Why not use an ATU at the feedpoint to optimize the match across most HF bands? This only becomes practical with a light-weight battery-powered, RF-sensing ATU mounted directly at the “bare wires” from the loop’s geometry. That’s what I did here to create what I call the Delta Vee AutoLoop. I use a $40 used surveyor’s tripod without the head made by Manfrotto. It was purchased at a local electronic recycling center but I bought another on eBay for the same price. The head is what surveyors want so one without it is far cheaper. It has a standard bolt that I connect to an adaptor for the mount point as explained in the PW article.

Randy K7AGE says he’s building one to use on his parked truck when out doing POTA or other portable operations. This antenna appeared in the January 2026 issue of Practical Wireless.

Random Copper Stick

I had been puzzling over these carbon fiber masts since they came out. My friend George KJ6VU cautioned to me that they wouldn’t load up and they played havoc with his Packtenna wire antennas if they come in contact with them. So, bah humbug! Then I ran across Ben VE6SFX’s Youtube video on an experiment with on using Faraday tape on the outside of the carbon fiber mast. He said it worked as a random wire type of antenna! So, after working my brain for months on an angle for this, Ben’s experiment gave me a direction.

The Random Copper Stick was built by using a carbon fiber telescoping mast and copper tape—both 1 inch and 1/8″ widths—applied from the bottom to the top for each section of the disassembled mast. The very top section was removed as it was way too small to hold the tape. This gave me a reasonable length for a random wire antenna. My experimental measurements with a 17′ wire (20 meter measurement) showed a fairly clear phenomenon that Ben didn’t get into in his Youtube video. As shown below in a slide from a talk that I give to clubs on these experimental antennas, the carbon fibers disturb the relationship between the physical and electrical lengths of the wire as they are closely connected to the mast. (Score one for George KJ6VU’s observations!) Thus, using a 9:1 Unun with the mast works very well with an ATU at the transceiver. To quote my lawyer friend, Mike N5DU, I was shocked and amazed at how an antenna that I was convinced would not work turned out so well.

If you fancy taking a walking stick to operate portably, consider the RCS. It’s very easy to build, back and put up. I built one for my friend Scott K0MD to take with him on his trips to pair with his Icom 705. My article on the Random Copper Stick appears in the February 2026 issue of Practical Wireless.

Wave Caster Vertical

It is scheduled to appear in the April issue of PW but that should coincide with Spring Break weather at the beach. You can build the Wave Caster to Hang Ten while working some HF bands, lol. This one is also very easy to setup if you have anything in the portable site environment to clamp the mount. in the Wave Caster, I use an idea that Chuck KK6USY published on his Youtube channel in a coujple of videos. Particularly, he solved the problem of winding an antenna wire around a spool without it getting too much stress and eventually breaking. Chuck used a small resin reel with a ring terminal to solve this problem. Well, that solved a problem I wrestled with on ways to multiply antenna designs using these inexpensive carbon fiber masts with wire that wouldn’t take much time for the portable operators. (Not all have a half day to go to a POTA site that can be far, far away with a lengthy setup.)

With a Super-C photography clamp, almost any sturdy surface can be used to “brace” the vertical so it stays up while the temporary operation plays out. Just don’t forget it when you leave because I can tell you it is easy to do! This one is scheduled as of this writing to appear in the April issue of Practical Wireless magazine.

I have a couple of other designs that I am finalizing as the wild weather in the South permits. They may appear in PW but I’ll post a notice here if they do.

My time at Mayo Clinic was well spent. I cannot overstate how positive the medical treatment there was. Mayo treats 26,000 prostate cancer patients per year and have been rated #1 for many years. There was never a moment where I felt like I was a number on a lengthy list. I was fortunate to get connected with Dr. Igor Frank there as the “top gun” on robotic prostate cancer removal. I gave him a small momento as an expression of my appreciation as I was discharged. I understand that it may have made an appearance at the Department Christmas Party.

EiffelTenna is in Practical Wireless

My bespoke portable HF antenna, called the EiffelTenna, is featured in the October issue of Practical Wireless. I was inspired by a video of Jim W6LG on his Youtube Channel as well as the further work of Jason VE5REV via Twitter (X). It’s a fun build, inexpensive, is very portable, and works 40, 20, 15 and 10 meters. I use Faraday Cloth for the counterpoise and place the tripod directly on it.

The 40 meter operation works as a center-loaded vertical, something I posted on regarding the inductor coils recently. If you intend to build the EiffelTenna, check out that article too. The EiffelTenna base alone would be good for Technicians since it works on 10 meters without a whip or coil. A stainless steel whip on top of the tripod makes for a solid vertical with its own mounting base. For windy conditions, I use some 1lb ankle weights attached to each tripod leg using the built-in velcro straps.

Shown below is the EiffelTenna deployed for testing on my driveway. (Click for full image) It is setup for 40 meters using a JPC-12 inductor coil. Others work as well or better so this was just the option used here because it’s adjustable. The RF sweep has the coil bypassed using KB9VBR’s trick for use on 20 meters. Nearly 50 ohms with SWR of 1.06 at 14.154 MHz. Note how relatively small the counterpoise cloth is in this picture.

This full antenna system packs down into an inexpensive camera tripod bag ($16 via Amazon). A RigExpert antenna analyzer is underneath the Faraday Cloth for matching in the field. Coax from RG-316 with a ferrite bead choke is wound on a wire winder printed by my public library for the cost of resin ($4). Blue ankle weights were purchased at Academy Sports while on sale.

The EiffelTenna uses traditional vertical antenna concepts with unexpected objects serving as both a ground mount and a radiating element. Thanks Jim W6LG and Jason VE5REV for the inspiration!

Get a load of this…

Ground-mounted verticals are all the rage these days in portable HF operations. This is particularly true in POTA activations. We all like to get extra mileage out of our verticals in terms of their frequency range and efficiency, no?

One method is to add an inductor to the radiating element to extend what its length looks like for RF resonance. Some versions of this are to bottom-load the vertical (Wolf River Coils does this with their Sporty Forty coil) as well as center-load it (as does Chelegance does with some of their JPC line of verticals). There are top-loaded designs, too.

An issue the portable HF operator might face if they create their own vertical antenna system is determining the value of the inductor coil. I’ll walk through this briefly to illustrate one problem that many vendors create for them in their product offerings.

Shown above is a center-loaded vertical that I’ve designed. It’s called the Eiffeltenna because of the similarity to the Eiffel Tower from the tripod legs. The details will be forthcoming once it is fully tested but the focus in this article is is that it is center-loaded as the inset photo illustrates.

What inductance value should I use? It all depends on the band, height before the coil’s insertion, and the total height of the vertical itself. Oh, and the ground and counterpoise element can play a role as well. Here, I’m using a 42″x35″ sheet of Faraday Cloth on a washed gravel driveway next to my garage. While this is far from good ground conditions, it functions very well as shown in an RF sweep below.

There are a number of calculators to help hams answer these questions. One is from 66pacific.com. I’ve placed a screenshot of the calculations for this test antenna below. The design goals are for the 40 meter band (7.0 MHz). But I also want to get 20 meters available, too. The total height of the antenna is specified as 16.75′. The coil is inserted at 7.5′ so what is the value of the required inductor to make a 20 meter vertical resonant on 40 meters here? According to this calculator, we need a coil that measures 12.1 micro-Henries.

One option is to simply build a fixed (non-adjustable) coil for this value. There are many online coil calculators for this. It is a desirable option unless there might be another band or the ground counterpoise system is very different or something else that changes things here. The other option is to purchase a coil from a number of vendors. One gotcha: very, very few actually tell the customer the inductance value for their coil (or the range if it’s an adjustable one)! They usually just say it’s “for 40M” referring to their own commercial antenna product for which it is an accessory.

Since I have several coils like this, I used one of my calibrated bench LCR meters (HP 4275a @ 200 KHz) to measure the value or range of values for several commercially available inductor coils. The results are in the table below. I have included three adjustment settings for the variable coils and the Q value. One definition of Q is “The quality factor (Q factor) is defined as the ratio of reactance to resistance, indicating efficiency at a given frequency.” For us, the importance of Q is “A higher Q value signifies lower losses and better suitability for high-frequency applications, as it implies a smaller ratio of resistance to inductive reactance.” So Q is an additional measurement about that inductor’s value that shapes how effectively it works.

While the MFJ open-air coil is no longer being manufactured, it is in wide circulation in the amateur radio community. It has a wide range, from 0.4 to 17.1 uH with corresponding Q values of 0.5 to 5.8. While the Mad Dog adjustable coil (sturdily built, I might add) has a wider range (0.73 to 28.3), it has somewhat low Q values (0.3 to 0.6). The Chelegance JPC-7 also has a wide range of inductance settings, from 0.5 to 22.8. Like the Mad Dog coil, the JPC-7 Q values are not great at 0.33 to 0.18 (double checked this figure). Here’s where one coil, larger than the rest, shines in this table. The Wolf River Coils Silver Bullet 1000 has values from 2.73 to 80.3, allowing a larger frequency range for loaded vertical antennas. Equally impressive is that the Q values range from 4.3 to 13.5 at the same time. All of these adjustable coils would fit the requirement of adding a 12.1 uH value at the center point of the vertical antenna shown above.

I included another coil from Wolf River, their fixed value Sporty Forty. They don’t tell the buyer what value it is, just that it’s an accessory for their ground-mounted whip antennas to get them to also work on 40 meters. I have two and they’re well built. Their value is 8.3 uH. There is a clone from China that is also 8.3 uH. Perhaps because of different manufacturing processes, the WRC coil has a much higher Q value at 8.6 than the clone from China has at 2.5. For these fixed value coils, it is key to realize what inductance value they have because neither would work in the center-loaded vertical example used here.

There is a very neat “bypass” trick created by Michael KB9VBR, published on his Youtube Channel. My version is shown at left. It’s simply a set of pigtails attached at the top and bottom of the coil with Power Pole connectors on each end. Plug them together, the coil is bypassed. Unplug them, and it’s in the driven element. Takes about 15 minutes or so with materials that you likely already have it you’re an antenna builder. If not, these parts are very inexpensive via online vendors.

This bypass trick can be used with any inductor coil so keep it in mind if you build a center-loaded vertical like I’ve done here. I don’t have to bring down the full vertical whip by unscrewing it, physically removing the coil, and replacing the whip. I can just reach up, plug or unplug the pigtails, and the vertical is either on 20 or 40 meters. This assumes that I’ve already done two things in the case of the Eiffeltenna center-loaded vertical.

Getting it tuned spot-on for 20 meters is fairly easy using the Faraday Cloth for the counterpoise field. It is a precursor for switching in the adjustable coil, such as the JPC-7, as shown above in my driveway. This is so that the coil can than then be adjusted to the correct uH value to load the antenna for 40 meters using an antenna analyzer. Once this is accomplished, marking the coil makes the process almost automatic during setup in the field. Checking it with an antenna analyzer, though, is always a good thing (ask me how I know, lol).

These vertical antennas can be configured in many ways but I hope that this article is useful to the portable operator who wants to operate with multiple band options using a quick setup vertical antenna. The Eiffeltenna, inspired by a tripod experiment published by Jim W6LG on his popular Youtube Channel, and further work by Jason VE5REV, fits that bill. Extend the tripod, add the coil and whip, placed it on the Faraday Cloth rectangle, connect the ground wire to the Cloth and the coax, and you are largely ready to go.

I’ll be publishing more about this very portable antenna once I’ve completed testing it. However, getting a load of the principles in this article applies to many, many vertical antennas. Get a the load of the coil you’re buying before the purchase!

Five-band HF Linked Dipole [updated January 2025]

An improved build

This antenna was first described in the November-December 2023 Communicator. After a year of using it, I’ve developed some improvements. - Updated January 2025

I appreciate inexpensive but effective antenna design. Sure, you can spend hundreds of dollars to buy a multiband antenna for POTA or GOTA but they are so simple to build, why would you want to? You can enhance your skills and communication capabilities by constructing custom antennas.

One popular and versatile option is the multi-band HF dipole antenna often called a segmented or linked dipole. This antenna design allows for effective communication across multiple HF bands by connecting or disconnecting sections along its length making it an inexpensive asset for ham radio operators, particularly outdoors enthusiasts and those needing a light, packable wire antenna that can be erected almost anywhere, and with good results—better than an end-fed, because each segment of the antenna is pre-tuned during construction, and can be used safely even when no antenna tuner is available.

Ideally it is hung from a pole or tree branch at 20 feet (6m) as an Inverted V, with the center point high and the dipole legs spread at least 110-120 degrees. I have worked the globe with this set-up on sideband and 20 Watts.

 

Oly one side of the dipole is shown 

As before, each of the five sections is cut to the band so no tuner is required. It is a marvellous POTA antenna, far better than any vertical, Hamstick or commercial antenna that I have tried.

You can read/download the updated article at: https://bit.ly/LinkedDipole

~ John VE7TI



Long Duration M-Class Flare, and More (Livestream)

This livestream recording is from September 1, 2024 – the NW7US Radio Communications Channel Livestream.  We do this livestream every Sunday at 21:15 UTC.  Here is the link to the livestream from this past Sunday:

The livestream list is here:

https://www.youtube.com/@nw7us/streams

I hope to see you in our livestream live chat, during the next session on Sunday, at 21:15 UTC.  See you there!

 

Livestream: Space WX, Propagation, Amateur Radio – Sundays

Join us, every Sunday at 21:15 UTC (5:15 PM, Eastern Daylight Time, 4:15 PM Standard), for an informal livestream chat session about:
– current space weather — the Sun/Earth connection — including sunspot activity, solar x-ray flares, and geomagnetic activity, as well as,
– current radio signal propagation conditions on the shortwave (high-frequency, or HF) radio spectrum. We also discuss,
– amateur (ham) radio, shortwave radio, and other related topics such as HF antennas (dipoles, doublets, Yagi antennas, and so on).
You can ask questions, and we will discuss some of them now, and some of them in upcoming videos.
Join us every Sunday for Livestream at 21:15 UTC

Join us every Sunday for Livestream at 21:15 UTC

Don’t forget to click ‘Subscribe’, ‘Join’, then, set the Alert Bell to “All” – so you don’t miss any session! You can ask your questions early, on this post.
Every livestream is posted here, so bookmark this link:  https://www.youtube.com/@nw7us/streams
See you there!

Exploring Shortwave Radio Signals: A Peek into Non-Local Communications

Curious about what you can hear on shortwave ham radio? This video is a brief survey of the diverse world of communications on the shortwave spectrum. Expand your radio horizons and enhance your emergency communication preparedness by tuning in to the world of shortwave ham radio.

If you’ve started delving into radio communications beyond local stations and channels, like VHF and UHF, you’re in for a treat. Shortwave radio opens up a whole new realm of signals to explore, including emergency communications vital during natural disasters.

[embedyt] https://www.youtube.com/watch?v=pIVesUzNP2U[/embedyt]

Shortwave radio covers a range of radio frequencies from 3 kHz to 30 MHz. This spectrum is home to a diverse array of radio signals that cater to various communication needs, making it a hub of activity and connectivity.

Within these high frequencies, you can tune in to a multitude of transmissions, from transoceanic air traffic control communications to the chatter of ships navigating the vast seas. Imagine hearing the voices of fishermen, much like those on your favorite reality TV shows about high-seas fishing adventures, along with military communications and the vibrant world of amateur radio enthusiasts.

One of the remarkable features of high-frequency (HF) radio is its ability to propagate signals over long distances, transcending line-of-sight limitations. This means that HF radio enables communication between different regions and even continents, fostering connectivity across vast distances.

During times of crisis and natural disasters, shortwave frequencies become invaluable for emergency communications. When local infrastructure falters or is disrupted, shortwave radio serves as a vital lifeline, facilitating critical two-way communications in and out of disaster-stricken areas.

Explore the fascinating realm of shortwave radio, where distant voices blend with essential information, bridging gaps and connecting communities in times of need. Uncover the power of HF radio to transcend boundaries and provide lifelines when they are needed most.

In this video, I give you a glimpse of the voice and data transmissions I pick up on my high-frequency amateur radio transceiver (in this video, an Icom IC-7000). In later videos, I will dive deeper into specific types of HF communications, such as aeronautical trans-oceanic signals.


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