KB6NU's Ham Radio Blog

KB6NU's Ham Radio Blog

Gear/Gadgets

Zero Retries Digital Conference to be held on Saturday, September 13, 2025 in Everett, WA

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I should have posted this sooner. My bad. If you’re in the Northwest and are interested in digital communications, please consider attending this conference in person. If you’re not, you can still sign up to attend the sessions virtually. There’s even an option for your club to attend virtually….Dan

We are pleased to invite you to the Zero Retries Digital Conference (ZRDC) that will be on Saturday, September 13, 2025 at the Edward Hansen Conference Center in Everett, WA. Due to the pandemic and other reasons, there has not been an in-person Amateur Radio digital conference for several years or any known plans for upcoming conferences. With GNU Radio hosting their conference at the same venue the week prior to ZRDC, Zero Retries seized the opportunity to bring back the in-person Amateur Radio Digital Conference to the Pacific Northwest. However, if people are unable to travel, there are alternative means to participate on the conference page link below and on the registration form.

About Zero Retries

Zero Retries is a unique independent newsletter that promotes technological innovations in Amateur Radio. The Editor, Steve Stroh N8GNJ, writes the majority of the newsletter with an occasional submission by one of his readers. Steve refers to Amateur Radio as, literally, a license to experiment with and learn about radio technology. He often jokes, but is serious, that radios are now computers… with antennas.

About the ZRDC

Planned presentations and demonstrations will be designed to enhance the skills and knowledge of the participants with topics such as but not limited to the IP400 Networking Project, M17 Digital Voice/Data system, MMDVM-TNC data system, ARDC’s 44Net VPN, software defined radio (SDR) and AREDN, HamWAN and other Amateur Radio microwave networking.  Attendees will have the opportunity to connect with peers, and discover innovative technologies that are shaping the future of Amateur Radio. A call for papers has been sent, which will provide the opportunity to learn from leading experts. The ZRDC 2025 will highlight the resilience and adaptability of the Amateur Radio community in the Pacific Northwest by embracing new platforms and technology that continue to foster the passion for radio communication.

In closing, I have created various ticket prices and multiple ways to participate. Please share this information as you see fit with others that might be interested. I have included the links below for registration and the conference. If you have any questions, please don’t hesitate to contact me. Thank you for your time and consideration and hope to see you at the conference.

Sincerely,
Tina Stroh KD7WSF
Business / Conference Manager
[email protected]

Zero Retries Newsletter
https://www.zeroretries.org

Zero Retries Digital Conference 2025
https://www.zeroretries.org/p/conference

Registration for ZRDC 2025
https://lp.constantcontactpages.com/ev/reg/7852x9m

The 2025 Four Days in May Symposium: An Introduction to LTspice, A Tube Transmitter for SOTA, SSB for the QMX, and more

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In years past, you could always count on a QRP-ARCI Four Days in May (FDIM) talk by Rev. George Dobbs, G3RJV. You might never know what the subject would be, however. As Bill, N8ET, put it, “He always submitted a paper for the FDIM Proceedings, but would often talk about something completely different.”

G3RJV became a Silent Key in 2019, but Jack Purdum W8TEE, Ashhar Farhan VU2ESE, and Hans Summers G0UPL have all stepped in and picked up the slack. All three have become FDIM regulars, and each presented interesting talks at this year’s FDIM. And, to round out the lineup, we were treated to talks by N8ET, WA5BDU, AI6XG, NT7S, and VK1UN as well.

Click on the video link next to each title to watch the recorded video.

The T41EP: Seven Years Later (video)

Jack W8TEE and Al AC8GY presented a short history of the T41, their software-defined transceiver (SDT) that they’ve been working on for the past seven years. Jack recalled that the T41 had its birth on the drive home from a Field Day trip in 2018. During that trip, Jack and Al hashed out some of the basic requirements, including:

  • It would be a software-defined transceiver (SDT).
  • It would have a spectrum/waterfall display capable of displaying up to 192 kHz of bandwidth.
  • It would be self-contained and not need a PC or laptop.
  • It would support CW and SSB with up to 20 W output power.
  • It would operate on the 80-meter, 40-meter, 20-meter, 15-meter, and 10-meter bands.
  • Both the hardware and software would be open-source.
  • It would be affordable for someone whose income was mowing lawns over the summer.

They explained how they made their design decisions, including how the hardware and software has evolved over the years. They also discussed some of the benefits of sticking with a project over several years. I think that this approach has certainly paid off. There are more than 1,000 T41 units currently in the field, and if this talk is any indication, there will be more in the future.

A QRP Messaging System Using FT8 Technology (video)

In this talk, Farhan, VU2ESE, described his software for passing short messages using FT8 technology. He has currently implemented this software on the zBitx transceiver, but it is still in beta mode.

VU2ESE’s paper is not, unfortunately in the proceedings, but if you’re interested in obtaining a copy, you can contact Farhan directly. Look for Farhan’s specification for his messaging software in the next issue of QRP Quarterly.

An Introduction to LTspice (video)

Nick, WA5BDU, then introduced the crowd to the wonders of LTspice, a free software package that allows you to simulate analog circuits. In addition to the analog simulator, the package includes a graphical interface that allows you to input circuit schematics and view waveforms. This software is being developed and maintained by Analog Devices and is available for Windows and Mac OS.

In his talk, Nick quickly ran through the features of LTspice using a simple transistor amplifier as an example. He also showed how to analyze crystal filters using the software.

In his paper, the author asks the question, “Is it (LTspice) hard to learn?” His answer is, “You can learn to draw a schematic and run a simulation in 30 minutes or less. You can also use it off and on for several decades and still have a lot more to learn. Sort of like electronics itself.” As this talk demonstrated, this is certainly the case.

A Project for the Decades: A SOTA CW Tube Transmitter (video)

This talk was a lot of fun. This project had its genesis in an article found in the March 1967 issue of Electronics Illustrated titled, “A 1 Bottle Xmitter for 40.” Dan Koellen, AI6XG, took that circuit and adapted it for portable operations, namely Summits on the Air (SOTA).

One of the challenges Dan faced was powering the transmitter with a 12 V battery so that it could be operated portable. The original project plugged into an AC outlet and included a power transformer to supply the 6.3 V filament voltage and the high voltage on the plate. Providing the correct filament voltage was easy—Dan used a 12AQ5 instead of a 6AQ5.

Supplying the high voltage was a bit trickier. Fortunately, he found a DC-DC converter designed to power Nixie tubes, which require a voltage of approximately 180 V. Not only did he find one—the Omnixie NCH6300HV—that could output up to 230 V, they were electrically quiet as well.

To implement the transceiver functionality, Dan used a QRP Labs QCX as the receiver and keyer, along with a T/R switch and bandpass filters that he designed for this project, Dan successfully activated W6-NC-402. He made seven 40-meter CW contacts, including two summit-to-summit QSOs. According to Dan, “The fun factor was a Spinal Tap 11 out of 10.”

A History of FDIM (video)

Right after lunch, Bill, N8ET, ran through some of the history of Four Days in May, dating back to when it started in 1996 at the Days Inn Dayton South. The organizers planned for 50 attendees, and were quite surprised when more than 100 registered! Bill attributes this to the great slate of presenters, including L.B. Cebik W4RNL, Dick Pascoe G0BPS, George Dobbs G3RJV, Gary Breed K9AY, George Heron N2APB and Joe Everhart N2CX, and Rex Harper W1REX.

The proceedings has the tables of contents for most of the symposium proceedings, and I’d encourage you to get a copy if you weren’t fortunate enough to attend the event. It’s really quite impressive the number of quality talks and projects that FDIM has supported over the years.

Beyond the ‘612 (video)

Since its release in 1987, the SA612 Gilbert Cell mixer, and all its variants, have been used in countless QRP projects. This era is, however, coming to a close. No new parts have been manufactured since 2022, and soon, new parts will be unobtainium.

This situation prompted Jason Mildrum, NT7S, to search for an alternative. His search was made more difficult because so many radios now are software-defined radios (SDRs) and don’t require mixers the way that superheterodyne radios do. Fortunately, Jason discovered the Maxim MAX268x series. Although designed for microwave applications, Jason concluded that the parts could be used for HF QRP radio projects after a fairly comprehensive series of tests. Using these parts, he built a QRP transceiver, with which he has completed several successful POTA activations.

At the end of his talk, Jason hinted that a return of Etherkit, his kit company, might be in the cards. Stay tuned for that.

Bringing SSB to the QMX (video)

Hans, G0UPL, opened his talk by apologizing for taking nine whole months to implement SSB on his QMX transceivers. I don’t know about you, but I think it’s rather remarkable that he was able to do it in such a short time! It would have taken anyone else much longer to do it.

Hans then launched into an explanation of how he was able to achieve this feat. After a review of digital signal processing (DSP) basics, he jumped into an explanation of polar modulation, the technique used in the QMX to generate single sideband. Hans’ paper in the proceedings includes references to papers which really get into the details of how polar modulation works, if you’re so inclined to read them.

Hans also got into some detail on his development process. After some initial failures, he decided to simply try the code that runs then uSDX and was quite surprised that it actually worked on the QMX. That began a series of improvements that resulted in the software that QMX users can now download and run on their radios.

I can’t really say that I understand everything that’s going on, but I think that with some review of Hans’ paper and some of the others that he references, I could get a better handle on it. I do know that his talk has inspired to complete the QMX kit build that I started months ago.

Stealth Operations from Hotel Rooms and Other Unlikely QTHs (video)

Ross Valentine, VK1UN presented the last talk of the day. It described his operations using QRP radios and short wire antennas from a number of “unlikely” locations that he’s been in around the world.

As far as radios go, small and light are the ticket. He has a selection of QRP Labs’ QCX and QDX radios, and uses small lithium batteries to power them. To run digital modes, he uses a Raspberry Pi 400 with a small LED/LCD display.

For antennas, he favors wire-wrap wire, often wound on a fishing reel. He notes that the wire is light and very difficult to see, even in bright sunlight. He tunes the antennas with a variety of homebrew tuners, including simple LC tuners, Z-match tuners, and FRI-match tuners, some using homebrew variometers for the inductors.

With this simple gear, Ross’s results have been impressive. He showed plots of his WSPR signal being spotted all around the world.

If these talks don’t inspire, I don’t know what will. I mentioned earlier that Hans’ talk has inspired me to finally get my QMX working, but I’m now also motivated to play around with LTspice, and I have some ideas for tube circuits that I want to build as well. The trick is going to be completing these projects before next year’s FDIM, when I’m sure another all-star lineup of presenters will inspire me to tackle yet more projects.

To get a copy of this year’s proceedings, contact Bill, N8ET at [email protected]  or   [email protected].

Buttons are back, baby!

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Several years ago, I got a good deal on a Flex 6400 and thought I’d give it a try. It’s a great radio, and I enjoyed using it, but after a couple of years, I decided to give it up and buy an Icom IC-7610 instead. The main reason was the user interface—the IC-7610 has real knobs and buttons instead of just a computer screen to control its functions. Maybe I’m just being old school (I am certainly getting old), but I prefer real knobs and buttons, even if those knobs and buttons are just providing digital inputs to the processor controlling the radio.

Recently, I’ve run across a couple of articles that back me up on this. The first, “Touchscreens are out, and tactile controls are back,” is an interview in IEEE Spectrum with Rachel Plotnick, an associate professor of cinema and media studies at Indiana University in Bloomington, and a leading expert on buttons and how people interact with them.

She says that while touchscreens are a useful interface, people are becoming somewhat fatigued by the use of them. “People seem to have a hunger for physical buttons,” she says, “both because you don’t always have to look at them—you can feel your way around for them when you don’t want to directly pay attention to them—but also because they offer a greater range of tactility and feedback.”

She also said something else I found interesting. “Buttons tend to offer you a really limited range of possibilities in terms of what you can do. Maybe that simplicity of limiting our field of choices offers more safety in certain situations.”

I might say that it also makes the user interface more straightforward and easy to understand and use. Take the receiver incremental tuning (RIT) control, for example. I use this control frequently on my IC-7610, I press a button to turn it on and a knob to set the offset. On the Flex, however, using the SmartSDR software, I’d have to go to the X/RIT menu, click on the RIT button on the screen, then set the offset by clicking right or left arrows or by typing in a text box. It’s just not as simple to do as on the IC-7610, so I found myself using that control less often.

ICOM IC-7610 transceiver
On my IC-7610, the RIT controls are conveniently located in the lower right-hand corner.

The second article is “Subaru is bringing back physical knobs and buttons in its cars.” The article begins, “To the relief of practically anybody who drives a car regularly, Japanese carmaker Subaru has brought back physical buttons and knobs for its 2026 Outback midsize SUV. It’s yet another sign that carmakers are finally starting to listen, ditching massive touchscreens that have taken over a vast number of vehicle controls in favor of tactile buttons, switches, and knobs.”

Of course, touchscreens are the appropriate choice for many transceiver functions. The IC-7610 touch screen not only displays the waterfall, but also lets you select a signal by touching it on the screen. That works great for me.

The lesson to be learned here is that a good user interface can help increase sales. These days, almost all of the radios from the major manufacturers are so good that the average ham can’t really detect a difference in performance. That leaves the user interface as one of the differentiating features, and you’d think that a more usable user interface would sell more radios. And, it appears that physical, tactile buttons and knobs are going to be a part of that user interface.

Will tariffs affect the cost of ham gear?

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A friend of mine asked me the other day how the proposed tariffs will affect the cost of ham gear. Not being an economics guy, I really have no clue, except to say that prices will probably go up.

Well, today I came across an email from Connect Systems, who import radios for digital communications.

Here’s their analysis:

Tariffs

The mark-up for amateur products in not very high. The following is how we figure the cost of the product:

CS750 cost to manufacture…….$115.00
Shipping………………………………..$15.50
Credit Card Cost ………………………$9.56
Tariffs at 25% ……………………….$28.75

Total out of pocket cost………….$168.81

Selling Price …………………………$239.00

Profit = 239 – 168 = $71

Now lets assume the tariffs are at 100%. The analysis is now as follows:

CS750 cost to manufacture…….$115.00
Shipping………………………………..$15.50
Credit Card Cost ………………………$9.56
Tariffs at 100% ……………………$115.00

Total out of pocket cost………….$255.06

Selling Price ………………………….$239.00

Profit = 239 – 255.06 = $(16.06)

If I don’t change the selling price, I would loose $16.06 for each radio sold.

The above analysis does not cover the cost of things such as cost of running the on-line store, salary, and other business expenses.

While I do not expect the tariffs to be set at 100%, I would be very surprised if the tariffs do not increase from the current rate.

We anticipated the tariffs and we bought a large stock of our standard products. We will keep the price the same until we run out of stock. While I cannot predict the selling price in the future because I do not know what the tariff rates are going to be, you can expect some type of increase.

When you buy direct from a Chinese company, you will not see a price increase. However, the tariffs are going to be paid by you before it is delivered.

Of course, who knows what the final tariffs, if any, will be, but this is something to keep in mind. It was reported this morning that car sales have jumped in anticipation of the tariffs raising automobile prices. Crazy times.

Videos: Single sideband, HAMNET update, HF propagation

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Introduction to SSB

This is an Air Traffic Command instructional video describing the theory behind single side band (SSB) modulation. Dig that jazzy intro music!

HAMNet Update

HAMNET (Highspeed Amateur radio Multimedia NETwork) is a fully-independent amateur radio wireless network that provides data services. It’s a wireless internet, so to speak. It covers many regions in Europe and is even now growing fast beyond its European border. Hamnet is using international coordinated IP-address space of the AMPRNet (44.0.0.0/8) and Autonomous System (AS) numbers out of the 16-bit and 32-bit private AS number space to interconnect active regions by external Border Gateway Protocol (BGP) routing.

Here is an up date on HAMNET given at the recent FOSDEM conference.

Rohde & Schwarz on HF Propagation

Rohde & Schwarz produces some of the finest RF instrumentation in the world. They also produce great videos on RF topics. This one explains HF propagation.

No more “cheap Chinese electronics” from Ali Express?

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The Washington Post is reporting that tariffs may make orders from Chinese vendors more expensive. While the article specifically calls out Shein and Temu, orders from Ali Express could also be affected. The report notes,

President Donald Trump has revoked a nearly century-old tax loophole that saved companies from paying tens of billions of dollars in fees on imports, most of which come from China. The move, which was part of Trump’s executive order Saturday to impose tariffs on China, as well as Mexico and Canada, could affect businesses from Etsy sellers and family-run footwear companies to e-commerce behemoths. In fiscal 2022, 83 percent of total U.S. e-commerce imports used the loophole, known as de minimis, according to a government report.

Without the loophole, prices on orders to Chinese companies, such as AliExpress, could go up an average of 30 percent. For example, I recently purchased a Putikeeg paddle from AliExpress for $73.20. Without de minimus, that key would cost me $95. I suppose at that price, it’s still not a bad deal, but I’m certainly glad that I bought it before the price goes up.

I just logged into AliExpress, and it doesn’t appear that the price increases have hit yet. So, if you’re planning a purchase, you might want to do it now before they do.

UPDATE 2/10/25

The BBC reported this morning that Trump has revised the order on Friday to allow tariff-free treatment for packages from China worth less than $800, and that this would remain in place until “adequate systems are in place to fully and expediently process and collect tariff revenue.” So, I guess we just wait and see if this will ever happen.

Videos: Dick Norton N6AA on the ARRL, KL7AJ on the ionosphere, new HT has 10 m SSB capability

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Dick Norton, N6AA, on the state of the ARRL

Every year, Dick Norton, N6AA, the Southwest Division Director, reports on the ARRL at Quartzfest. As one of the audience members noted, this is perhaps the bleakest report that Dick has ever given on the state of the League.

One item that you might want to especially note is that at the 25:30 mark, Dick comments on the ARRL’s shift from a membership-based organization to being a corporation. If we’re no longer a membership-based organization, why pay to be members?

Eric Nichols, KL7AJ, on the ionosphere

The ionosphere is more complex than just a simple mirror for radio waves.

New Quansheng HT has 10-meter SSB capability

OM0ET gives us a little teaser video about an upcoming release from Quansheng. The TK-11 will operate on 70 cm, 2 m, 6m, and 10 m, including SSB capability on the 10-meter band. He notes that he’s not sure whether the firmware will be modifiable as it is for the Quansheng UV-K5.

From the trade journals: The rise and fall of Heathkit, Antennas 101, circular polarization

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The Rise and Fall of Heathkit

Steve Leibson begins this six-part series with, “If you came of age in the 1960s or 1970s and then later became an EE, chances are you’re more than casually acquainted with Heathkit. Many engineers started their budding careers by building one or more kits made by the Heath Company. I certainly did.”

Since this is a ham radio blog, I’d say, “If you came of age in the 1960s or 1970s and then later became radio amateur, chances are you’re more than casually acquainted with Heathkit. Many hams started their budding careers by building one or more kits made by the Heath Company. I certainly did.”

This is a remarkable series based on an interview with Chas Gilmore. Gilmore started as a design engineer at the Heath Company in 1966 and worked at the Heath Company on and off for more than two decades. He eventually became vice president of product development, marketing, and sales.

…read more

Antennas 101

Lou Frenzel, W5LEF (SK), was a prolific writer and editor. He was also a ham. Here, he explains antennas in way that we call can understand.

He writes, “Antennas are much more than simple devices connected to every radio. They’re the transducers that convert the voltage from a transmitter into a radio signal. And they pick radio signals out of the air and convert them into a voltage for recovery in a receiver.”

…read more

Understanding circular polarization

John Dunn writes, “An electromagnetic wave or signal traveling from “here” to “there” has an electrostatic field component that we call its E-field and whose direction we assign as the signal’s polarity. Often, the E-field is either vertical or horizontal as developed by a dipole structure or a ground plane antenna, but it can also be rotary which means it can be rotating around the signal’s axis of travel. The conventional terminology for that case however is not the word “rotary”, it is the word “circular”. We thus speak of vertical polarization, horizontal polarization, and circular polarization.”

I’m still not sure that I understand circular polarization after reading this article, but take a look for yourself.

…read more

 

 

AliExpress: a toybox for radio amateurs

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Flange-mounted resistor.
My original AliExpress purchase: a 250 W dummy load resistor.

It all started last February when I was induced into purchasing a 250-watt dummy load resistor for a couple of bucks from AliExpress. Since then, I’ve been bombarded with emails from AliExpress almost daily.

Normally, I’d unsubscribe from such mailings, or send them immediately to spam, but I’ve become really intrigued by the stuff they sell. Not only are the items for sale very cheap, some of them look like they could actually be useful.

I’m thinking that I’ll start a series of posts reviewing some of the ham radio gear you can buy on Ali Express. With that in mind, here’s my first review…

A cheap (but very usable) paddle

Dual-lever iambic padddle
This Putikeeg Auto Morse Keyer Double Oars Telegraph Key was my second Ali Express purchase.

I made my second purchase a couple of weeks ago: a Putikeeg Auto Morse Keyer Double Oars Telegraph Key. The cost of this key was $77.16, including 6% sales tax. It arrived in two weeks from China.

One of my motivations for buying this key was to check out the quality. I’m always being asked about what would be a good key for a beginner, and this seemed to fit the bill. The price is right, but I was afraid that, despite the nice photo, the key would be mechanical disaster.

I’m happy to report that this key is actually well worth the money. It arrived nicely packaged in a padded box, and after unboxing the key, I spent maybe ten minutes adjusting the contact spacing, Adjusting the contacts was relatively easy as the adjusting screws have a pretty fine pitch, which meant I didn’t have to fuss around too much to get the spacing I wanted.

There are four magnets in the base, meaning that you can place the key on a metal base so that it doesn’t slide around on your desk. The magnets have rubber feet, though, and it was very stable on the silicone shelf liner that I use on my desk to prevent keys from slipping.

I made several contacts with it that evening at 23 wpm, and the key worked very well. I couldn’t attribute any of the errors I made to the key.

One reviewer on eHam gave the key a poor rating because the finger pieces on his key were kind of rough. That wasn’t the case with my key at all. Both the metal and plastic finger pieces were very smooth and had a nice feel.

This key is not a Begali, but for less than 80 bucks, it’s certainly a decent key for a beginner. I will not be hesitant to recommend it when I’m asked again.

Onward and upward

There are a lot of other things on Ali Express that I’m thinking of buying. In some cases, I’ll keep the device. In others, I’ll sell it at a hamfest. The prices shown below all include shipping.

I could go on, but it’s dinnertime, and I’m getting hungry. If you are curious about something on Ali Express, but just can’t seem to pull the trigger on it, let me know. If it’s inexpensive, there’s a good chance that I’ll just buy it and then do a review on it.

Interesting Stuff: Pico-based SDR runs standalone, texting over HF, HamClock on WiFi

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There’s so much interesting stuff out there that I’m never going to get to it all. I blog about these projects, though, so that I don’t forget about them and to let others know about them. If you’v ever built or used one of these projects, please leave a comment below or email me directly.

Pico-based SDR runs stand-alone

Microcontrollers are getting to be very powerful. The Raspberry Pi Pico, for example, feature dual core processors, running at frequencies up to 150 MHz, with 520 kB of SRAM, and 4 MB of on-board flash memory. They’re very inexpensive, too. You can get one of these microcontrollers from reputable dealers for less than $8. If you’re willing to take a flyer on Ali Express, some of them are going for less than $2.

As shown in the video, this lets one build a software-defined radio (SDR) without a PC!

Think of the possibilities. One of the things that comes to my mind is to couple this with an Si5351 module and amplifier to make a small HF transceiver.

For more information:

Chirp to send text messages

PA3FWM has developed a new digital mode he calls LongChat that uses chirp signals with an audio bandwidth 300 Hz–2700 Hz. Pieter claims that LongChat is very power-efficient and offers good performance even at very low power.

For more information:

HamClock on a Raspberry Pi Zero 2W

Small printed-circuit board connected to a laptop via a USB cable.
Adam Drake, VE7SAL, coerced this Raspberry Pi Zero 2W to run HamClock.

The September-October 2024 issue of the Surrey Amateur Radio Club (SARC) Communicator has a great article on using a RPi Zero 2W to run HamClock. The unique thing about this implementation is that is uses the WiFi capability of the RPi Zero 2W to make, in effect, a HamClock server. With this running, you could then display HamClock on your laptop, a tablet, or even your phone.

For more information, see PE4BAS’s implementation of this project.