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The K1YPP Magnetic Loop Antenna

May 25, 2019

The K1YPP Magnetic Loop Antenna

Note to my readers of this blog: I’ve decided to expand the blog to include various other interests I have. Up until now everything that I’ve posted has been strictly about writing and author related topics. Since I have varied interests, such as ham radio, bicycling and hiking, for example, I’ll be including topics related to those fields. This post is about an antenna that I have been researching for several years for amateur radio (also known as “ham radio”). There is a Youtube video of this project at:


I’ve been living in a home owner’s association (HOA) for some time now and have been on the air as an amateur radio operator. There are challenges, but one can get on the air in an HOA.

I’ve been experimenting with Magnetic Loop Antennas, (MLA’s) for years. They are small, light-weight, and have excellent local electrical noise rejection. For years I had avoided building one because most of the designs involved a daunting array of expensive vacuum capacitors, fancy welding and brazing, special low-resistance materials, etc.

My new antenna would have to meet three requirements:

  1. Cost $50.00 or less (excluding remote tuning devices, such as motors, hydraulics, etc.).

  2. Cover 40, 30 and 20 meters.

  3. Have a minimum power limit of 30 watts ( for CW and PSK31).

The primary challenge is to keep resistive losses to a minimum. Many MLA designs use large diameter copper pipes and silver-soldered joints. Builders favor vacuum capacitors or butterfly capacitors that have no electrical contacts or brushes because the contacts will overheat.

Based on the calculations on Steve Yates’ (AA5TB) web page Small Transmitting Loop Antennas, I settled on a four-foot diameter for the desired frequencies. My initial prototypes used folded aluminum foil on PVC pipe, but the foil was too difficult to work with, especially if outdoors in a windy location. I then tried aluminum weather-seal tape and found success.


Parts before assembly. The PVC-to-CPVC adapters are not shown.

I formed the loop with 12 feet of the flexible ¾ inch Sharkbite PVC and used two straight pieces of a larger ¾ inch diameter PVC (Lowes # 23990) to form the capacitor. ¾ Inch copper tubing fits nicely inside this particular PVC tubing, without too much “slop.” I used a continuous piece of aluminum foil tape (2 inch width) spiral wrapped around the loop and down along the two tubes that formed the “capacitor.” The tape I used was made by Nashua Corp, and has a sticky back with a blue plastic cover over the glue. I didn’t remove the plastic, it made construction easier and less messy. The only soldering is the SO-239 coaxial connector. In the first prototype, I wrapped folded aluminum foil in a spiral around the loop and then around the vertical tubes, but the spiral proved to be problematic for the capacitor. The contacts between the spiral as it wrapped down the vertical tube provided contact resistance and the resulting high currents affected the SWR. I found a solution by leaving a gap in the spiral wraps so that the foil did not overlap or touch.


The capacitor is actually a form of “Butterfly” capacitor, formed by the outer foil on one tube, the “trombone” copper tubing, and the foil around adjacent tube. When purchasing the vertical tubing, make certain the 3/4 inch copper tubing will fit inside the plastic tubing. There are many variations so careful selection is necessary to insure the copper will slide inside the plastic tubing. To adapt the CPVC “TEE” fitting to the vertical tubes, I used a PVC-to-CPVC adapter (Lowes #65322) with a small section of Sharkbite tubing inside. The parts are all held together with some self-tapping screws, glue isn’t needed. With the dimensions used, the capacitor measures about 200 µF per foot, giving a total of about 100 µF/foot for the two legs being in series. The 40 M band needs about 160 µF of capacitance, so the legs have to be about 22 inches. The good news is, since the capacitor goes through two pieces of plastic tubing, the voltage rating doubles. PVC is rated at about 140 kV/CM, so this configuration should be good for about 20 kV.

Tuning the capacitor is a matter of sliding the “U” shaped copper tubing “trombone” up or down in the capacitor to achieve resonance.

I made a small feeder loop to couple to the main loop. I soldered a SO-239 coaxial connector to common household #12 electrical wire, about a foot in diameter. I then attached the small loop at the top of the MLA and coupled it tightly to the main loop. Using an antenna analyzer, I adjusted for best SWR. This proved easier than anticipated. A loop about one-fourth to one-fifth the diameter of the main loop worked best.



Simply cut the plastic pieces to length and plug them together. You can also use duct tape during the wrapping process to hold the aluminum in place. To form the U-shaped “trombone,” notch the copper pipe with a hacksaw or “crush” it in a vice, and then bend it to ninety degrees. For a more “finished” look, one can heat the copper to red-hot, then let it cool slowly. Then, fill it with sand or salt, then bend it over a round surface. Look around on Youtube for various methods.

Wrap the foil starting at the bottom of one capacitor tube, follow up around the loop and then down the other capacitor tube. Keep a small gap between windings on the capacitor tube, about a 1/4” is sufficient.

After wrapping the foil, mount the small loop with duct tape or tie wraps, and then insert the “trombone” copper tubing. The antenna is now ready for testing.


With an antenna analyzer

I used an MFJ antenna analyzer for the testing phase. If one is not available, see the instructions below for testing with a transmitter and receiver.

To test, push the “trombone” all the way into the capacitor tubes. Search above and below the expected frequency to find a dramatic dip in SWR. The coupling loop may need adjustment to get the lowest SWR. If the dip is below the 40 M band, withdraw the “trombone” until it resonates at the bottom of the band. If it is too high in frequency with the “trombone” inserted all the way, then there is not enough capacitance. Either the aluminum is not tightly wrapped around the capacitor tubes or the plastic tubes are too short.

Once you are satisfied with the adjustment, mark the copper tubing with a grease pencil to show where the 40 M band is.

Next, pull the “trombone” out a few inches and then find the resonant location for the 30 M band. Finally, do the same for the 20 M band. If your main loop is about 44 inches in diameter, there is a good chance it will work on 17 meters as well.

Using a transmitter and receiver

Use a VERY low power transmitter and an SWR meter. Caution: the currents and voltages around the capacitor section of the antenna are extreme. Even a few watts will cause serious RF burns. Be careful.

Move the “trombone” in fully and then tune around with the receiver until noting a marked increase in noise. This is where the antenna is resonant. Slide the “trombone” until it is resonant at the desired portion of the 40 M band and then apply a small amount of power from the transmitter and check the SWR. If the small loop needs adjusting, turn off the transmitter and cautiously adjust until the antenna is working as desired. Mark the copper tubing to indicate the band.

On The Air

Once you have tuned the antenna to satisfaction, mount it where no one can touch it when transmitting. With a loop diameter of 48 inches, the bandwidth is about 129 kHz on 40 M, and 293 kHz on 20 M. This is wider than many of the commercial MLA’s, but I was more concerned about efficiency and bandwidth. A larger loop is more efficient. A smaller loop can be better at rejecting local noise, but I found the combination here to be more than adequate. A wider bandwidth eliminates constantly re-tuning the antenna.

At a future date, I will post something on how to build a stepper motor driver for this antenna. Look around the Internet for existing designs.

As for maximum power, the antenna has consistently handled 100 watts on CW without heating or voltage breakdown. Since I only tested with 100 watts, it isn’t clear what the upper limit might be.

As for performance, that is a difficult thing to judge. My experience indicates that this antenna on 40 Meters performs almost as well as a G5RV at 35 feet, and as well as the G5RV on the higher bands.

Did the antenna meet the design goals?

My original design goals were modest: the antenna needed to cost under $50.00, operate on three bands, and handle 30 watts. Yes. In fact, it exceeded all the goals, it:

  1. Costs under $20.00 to build (not counting a remote tuning mechanism).

  2. Operates on 40, 30 and 20 M. One version, a slightly smaller loop (44 inches), also functions on 17 M.

  3. Runs well at 100 watts. The upper power limit is yet unproven.

This antenna is impressive. Over the last several months, I have worked many DX stations and maintained reliable communications in long-winded rag-chewing sessions. Not only is it a pleasure to use, it has been a rewarding homebrewing experience.

A 20 meter through 10 meter version of this antenna is possible. I have one where the main loop is 32 inches in diameter (81 cm) and the capacitor tubes are 20 inches (51 cm). The capacitor tubes can use PVC pipe, such as the straight version of the 3/4 inch Sharkbite product and 1/2 inch copper tubing.

73 de K1YPP

Partial parts list

Note: Lowes will ship to store if ordered on line





Charlotte Pipe ¾ inch x 10 ft, 200PSI PVC pipe


10 feet

Lowes #23990

Sharkbite PEX flexible tubing

13 feet

Cut short pieces to connect Tee’s Lowes #998500

¾ inch copper tubing, type M


5 feet

Confirm it fits in capacitor PVC tubing, Lowes #23792

¾ inch CPVC Tee


Sharkbite should fit snugly, Lowes #23760

¾ inch CPVC to PVC adapter


Couples Tee to capacitor PVC, Lowes #65322

Aluminum tape, 2 inch x 10 yards


30 feet

Plastic backed sticky tape Nashua Corp, #322

2014 in review

December 29, 2014

The stats helper monkeys prepared a 2014 annual report for this blog.

Here’s an excerpt:

A San Francisco cable car holds 60 people. This blog was viewed about 590 times in 2014. If it were a cable car, it would take about 10 trips to carry that many people.

Click here to see the complete report.

Rest in peace, Robin Williams

August 14, 2014

Robin Williams tragic death produced unprecedented grief. I admit I was very moved by his passing. I didn’t personally know him, but in some ways, maybe I did.

Our relationship was one-way, he talked and I listened. In most relationships, that would be unhealthy, but in ours, it worked. He made me laugh so hard I sometimes had tears in my eyes. Now I have tears in my eyes, and they’re still tears of joy, as tragic as all this is. He made me laugh, I can never forget that.

As I’m getting on in years, I’ve lost many that were dear to me. Many of my buddies from my military duty in the sixties are gone. My first serious girlfriend passed away in 2003. My parents are long gone. My kid brother was killed in Vietnam in ’68. There is a long list of people that I wish were still here. They’re not. I celebrate their lives, they each gave me something.

I loved Robin Williams’ work. However, I don’t think he did. Though he found his fame with his humor, he always wanted to be taken seriously. There were two Robin Williams; the comedian, and the serious actor. In my opinion, I think he wanted to be seen as a dramatic actor. Even though he landed some very serious parts, such as in Good Will Hunting, The Dead Poets Society, and Insomnia, he’s remembered for Patch Adams, Mrs. Doubtfire, Aladdin, Hook and others. For years I’ve observed his trajectory, and he always sought out dramatic work, but the public always loved him more for the humor. It was as if he were the worlds greatest painter, and yet he was known for his electrical engineering work. We, his viewing public could never fully accept him as a dramatic actor. I don’t believe Mr Williams saw himself on a par with the great actors such as Bogart or Brando. It always seemed he viewed his humor as an affliction, rather than a talent. Humor was his ugly twin brother, attached at the hip.

In our day-to-day lives, we tend to pigeon-hole people. I have an author friend, Bill  “Skywalker” Walker, that is extremely tall, about seven feet. I don’t believe a day of his life has gone by where someone hasn’t asked him if he is a basketball player. He has no interest in basketball, but loves golf. He recently wrote an excellent book on the topic, Tall Tales: The great talisman of height.  Similarly, I imagine that not a day of Robin Williams’ life went by where he wasn’t expected to be funny. I think Robin Williams was pigeon-holed as a comedian when all he wanted to be was a dramatic actor. I can only guess here, as I said at the beginning, we didn’t really know each other.

I’ve known my share of writers that have a similar dilemma, they write great non-fiction, but really want to write novels. Dave Berry is a great example. He has dozens of humorous books and has taken a stab at a few novels, but they’ve gone nowhere. How many of us have very successful lives in one field, but wish we were something else?

We, Williams fans, wanted more humor, and he wanted more ‘serious’. His depression amplified his frustration and he is no longer with us. We didn’t betray him, we just didn’t understand this illness that is depression. Apparently, even those closest to him didn’t.

Heart-bypass patients face serious depression issues following the surgery. After my six-artery bypass, in 2007, I was fortunate: no depression. In my therapy sessions I was surrounded by people that were having serious issues. I delved into this in chapter six of my first book, Three Hundred Zeroes. It was my hope that the book would find its way into the hands of bypass patients. I often wonder, with the many thousands of copies now out there, how many readers have undergone bypass surgery. Most don’t realize it, but Robin Williams was a heart surgery patient as well. Could it have added to his depression problems?


Robin Williams showing off his heart surgery scar.

There may never be another Robin Williams, he truly was unique. He had a mind like no other. Rest in peace Robin Williams, you gave us far more than you could ever know.

Need help with depression? Get help, don’t wait, we do care:

Anxiety and Depression Association of America, ADAA

National Suicide Prevention Help Line:

  • 1-800-273-8255 (1-800-273-TALK)



Kindle book pricing and how the big guys don’t get it.

July 10, 2014

I love to read. For some reason, as a young reader, I missed many of the classics. I’ve made up for lost time over the years by “catching up.” Books like The Catcher In The Rye, Of Mice And Men, White Fang and On The Road have been books that I’ve only read in the last twenty years or so. The same goes for movies, I’ve caught up on The African Queen, Casablanca, The Godfather and others in the last few years. How did I miss them? I don’t know, perhaps I just spent so much time outside when I was younger, I just missed them. That is a subject for another time.

Yesterday, I read a news piece on CNN about an author that was gored running with the bulls in Pamplona. Bill Hillmann, author of “Fiesta, How To Survive The Bulls Of  Pamplona.” How ironic. It occurred to me that I had not read anything much by Hemingway recently, so I decided to take a look online and see if I could find his book, “The Sun Also Rises.” I figured that, surely, by now, it must be on Kindle for an inexpensive price, or perhaps, even free. Surely.

The book was published in 1926 and is famous for its depiction of running with the bulls. I started hunting around the Internet for a copy. Much to my surprise, actually, I wasn’t that surprised, the cheapest “legal” copy I could find was $7.99, for the Kindle. I could also get a paperback copy for $8.48. The publisher is Simon and Schuster and they, as well as all of the other surviving publishers, don’t “get it.” I’m not going to pay that much for a book written in 1926, I’m just not.

There are illegal means to get a copy, the bit torrent servers have it out there, but I like to do my reading legally. Yes, there is some cost to putting the Kindle version online and I’d willingly pay, perhaps, $0.99-$1.99 for a copy, but $7.99…no way. This problem exists industry-wide. Any of the better known contemporary or classic authors that are still published by the larger publishing houses do this and they’re losing money.

Eventually, I found a print copy in our local library and rode my bike over and picked it up. It is a very old copy, but that’s okay, it is an old book. The publishers lost another sale of an e-book. I wonder how long it will be before they catch on?

Please do comment. Am I being weird or a curmudgeon? How much are you willing to pay for e-books?

Preaching to the choir.

March 13, 2014


Sometimes, preaching to the choir can be productive. Last night, I gave a presentation at our local authors club, The Authors Connection. This club was instrumental in getting my book published. The club was formed by Susan Klaus and is going strong. Susan’s latest work is Secretariat Reborn. If you’re a thriller reader, check it out.

My book came to be published because a speaker at the club, Ron Klein, did a presentation about using to publish your book. I was hooked. In no time at all, my book was in print, and the rest was history. It was my turn to “give back,” to the club.

I talked about book trailers. As I’ve noted many times before, on this blog, I detest most book trailers  (Jan 16, 2012 and Jun 30, 2011). It isn’t that I dislike trailers, I just dislike how many of them totally suck. The presentation last night was intended to show a few good ones and show the members how to create a “low budget” yet effective trailer. The intent wasn’t to show the authors things that they could mimic. The purpose was to give them ideas. They’re creative people, most of them will come up with something even better.

The very first thing I did in the meeting, was record a short two-minute book trailer. It was the simplest kind: an author talking to the camera. I chose discussing why the reader should read Three Hundred Zeroes. The purpose wasn’t so much to make a trailer as it was to demonstrate how to record the video, put it on the computer, and then upload it to Filming this live was a gamble. A slow link could take 15-20 minutes, but fortunately, it only took about a minute. My fallback plan was to start the upload, and then play a few favorite book trailers while we waited. I didn’t have to.

The pressure was on me, as the presenter, to nail the video correctly, the first time. There was no time to do a retake. Luckily, it went well, although my trailer was a little “stiff.” You can see it here: 


Prior to the meeting, I posted the notes at: Book Trailers for Sarasota Authors Connection. My intention was to give the audience an interactive page where they could view the trailers in more detail and my comments on why I chose those trailers. This eliminates their having to take notes and get web addresses incorrectly. Following the meeting, I included a link to the book trailer we did on location (which I obviously had to add later!).

I cannot attest to the quality of any of the books, I was merely interested in their trailers. They all had something that I liked about them, but perhaps not everything. Look that page over, watch some of the trailers and let me know what you think. Do you agree, or disagree? Do you know of a book trailer that you REALLY like or dislike? Post a comment, we’d like to hear from you.

Photo is Creative Commons, courtesy of Boston Library.

The fine print in writing contest submittals.

February 5, 2014
The Trader: Man With No Face, by RK Mann

The Trader: Man With No Face, by RK Mann

Rachel Mann, a local Florida author, is our guest blogger today. Rachel authors Sci-Fi thrillers. Her latest, The Trader: Man With No Face, reminds me of the George Lucas Star Wars series. 
Today, Rachel offers up information and cautions on getting involved with publishing contests. She specifically investigates the Amazon Novel Contest. 
Amazon has a novel contest for works that have not been published or have been self published. Submissions begin in February, 2014. You can view the terms at:
I read the terms and  the only prizes seem to be reviews in Amazon and (at the top) Publisher’s Weekly, plus Amazon publishing contracts. I was floored by what I found in the fine print. Look closely at section 5. Grant of Rights: 
you agree to negotiate the terms and conditions of a publishing agreement exclusively with Amazon Publishing for a period of 30 days after you receive notification from Amazon Publishing. If you and Amazon Publishing have not reached agreement after 30 days, you may offer the work to other publishers on the condition that before you enter into an agreement with another publisher, you will afford Amazon Publishing the last right to publish your Entry on the same terms and conditions offered by any other publisher, plus an advance against royalties 10% greater than the other offer… 
then check out section 9. Prizes:
…Amazon Publishing will determine the royalty rates to be paid under the publishing contract. If you are the Grand Prize Winner, you may not negotiate the publishing contract with Amazon Publishing, and you must sign it “as is” upon receipt of the executable contract (as described in Section 11 below) if you wish to enter into the publishing contract being awarded… 
The same applies to the first place winners.  If you read the posted contract details they don’t reveal much except the advance.Though they say in section 5. you can negotiate, in section 9. they say you cannot. Worse,  if you decline their deal, they have the right of first refusal – their terms being you must submit another publisher’s contract and they may match the contract and increase the royalty by 10%.  
In other words, if you don’t do their unknown deal, you will be negotiating in bad faith with anyone else. And since this contest is probably well known and Amazon’s terms are posted on the web, other publishers will know about it. Thus, why would any other publisher bother to even offer a contract, since they would know Amazon has the right to top it? Amazon claims the option to offer you a publishing deal, even if you don’t win, and bind you by the same first right of refusal. 
As I read it, Amazon can prevent you from ever getting another publishing deal on your work by just entering their contest. And they haven’t even paid you a dime. 
Of course, if you don’t care about your copyright, other rights to your work (film, tv, etc.), sequels and royalty rates, Amazon will give you a cash advance and reviews (presumably good) if you win. 
– Rachel Mann

 Thoughts? Comments? Have you ever entered a contest? Did you win, or place? How was your experience?

Some pointers on publishing in 2014

January 9, 2014

As is obvious, I’ve been absent from this blog for some time now. Being a “one-man show,” there is only so much time in the day to accomplish things. I believe that most modern-day authors, well know this. Some things have to give way to higher priority items. I gave a speech, about a year ago, on the state of publishing today, and what it means to aspiring authors. Here is a video of that speech. It is about twenty-minutes long and sums things up pretty well. Get a cup or tea, or coffee, sit down and enjoy…

Amazon recommends Three Hundred Zeroes:

August 1, 2013

Amazon recommends Three Hundred Zeroes:

Away, but not lost.

July 14, 2013

One of the difficulties of being an author that writes non-fiction is doing the research. True, fiction writers have the same challenge, but often they can use data that already exists. In my case, since I write about personal experiences, ones that are somewhat recent, I have to go out and “have” the experience.

I’m currently doing just that, and have been since the beginning of May. Jane and I started off on a cross county bicycle ride across Spain, from Barcelona to Santiago de Compostela. It went okay for about 500 miles (800 km) and then she had a crash. Her knee needed twenty-plus stitches and she was told she wouldn’t be able to ride her bike for at least a month or more. She could walk just fine, so we shipped the bikes home and are now walking around Europe.

Jane has been keeping an excellent blog on our adventures at:

Thus far, we have hiked across Portugal on the Portuguese Camino, about 600 km and now we’re in England. We walked about a week on the South West Coast Path, in Cornwall. The scenery there is stunning and I hope to one day come back and hike the whole 1000 km. Another book, who knows?

Anyway, this short update is to inform you that I am still alive and will return by mid-October or so with more data and research information to fuel more books. I’m investigating my Dad’s adventures over here during World War II. He was in the 82nd and 101st Paratrooper divisions and I’m finding it is quite a story. He would have been 100 years old this year.

Stay tuned.


Things just keep getting more and more complicated.

March 11, 2013
Technological marvels.

Technological marvels.

A few days ago, I received a problem report ticket from Amazon:

Text in your book is unreadable for readers using black or sepia color schemes.”

It is a rather cryptic message and didn’t give any details about solutions. It did give a link to the Kindle formatting page: Guide to Kindle Content Quality. The guide gave very little useful information about the issue.

Ultimately, I went off on an Internet search and eventually discovered that I wasn’t alone, others had received emails such as mine, but there were no real solutions. The original problem, which wasn’t readily apparent, is the newer Kindles, such as the Fire, can display the book with a black background with white text. Several authors took the attitude that viewing a document with white-on-black letters was so “80’s.” I didn’t exactly see this as a healthy attitude or solution to the problem. We authors can’t always know the reasons our customers do things.

I originally wrote and published my book using Microsoft’s Word. I no longer have Word, it proved too arcane and difficult to use, not to mention, expensive. I’ve since migrated to and their Writer tool. It is user friendly and offers all the same bells and whistles as MS Word, and is free! (they DO appreciate donations)

For reasons I won’t go into here, when I first published Three Hundred Zeroes, I was able to upload the document to Amazon’s Kindle site as a MS Word document. Recently, I had to make some changes to the document and decided to do all the work in HTML (a language used to write web sites). The tools I have are not very robust for such work, but I’m sufficiently comfortable with HTML at the source code level and can fix things where needed.

In January, I did an update of the Kindle version of the book, uploaded it to Amazon’s KDP site (their Kindle interface) and thought I was done. Then came the email, I wasn’t done, apparently.

I couldn’t find a solution in any of the OpenOffice forums, so I posted my problem. Usually, within an hour or two, someone will respond with a solution. I waited. Nothing. I then decided that I had to dig in and find the problem. It occurred to me that the HTML for the book has various “styles” defined. The styles guide the electronic viewing equipment (computer, Ebook, Iphone, etc.) with instructions on how to display the information.

After diving into the HTML code I found that it did indeed have some CSS definitions, and in there, I did find a few that explicitly defined that the text should be “black,” using code #000000. Black text, on a black background means a black screen!

The definitions defined the basic text (P)and a few of the headers (H2, H3 and H4) as black. I fixed just the “P” (for paragraph) and loaded it back into my Kindle simulator. Sure enough, I was now able to read white text on a black screen for the paragraphs and the H1 headers. Problem solved!. I went back and fixed all of the parameters to use “automatic” colors, instead of “fixed” colors.

It has since been posted and updated on Amazon. If you already have a copy of the book, pester Amazon for the updated version (11 March, 2013.) They probably haven’t sent out word about the fix yet, but if they get enough requests, they will.

Several technological areas collided to cause this problem. First of all, when I first wrote and published this book on Kindle, it wasn’t capable of being displayed in this fashion. Since I originally posted it with MS Word, it probably would have worked in the newer units, since I didn’t have CSS code defining colors. When I saved the file in OpenOffice as an HTML file, it wouldn’t allow me to turn on the automatic color feature, which means, let the viewing device control color. In spite of all of this, I’m really surprised that the Kindle code doesn’t inspect the CSS to see if there is a request for black print, on a black background. It should, and it should force the text to white under those conditions, that just stands to reason.

These technical devices we use these days are extremely complicated and I can only imagine that these sorts of problems will continue to crop up. They are designed by humans, and we’re not infallible.

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