I got my Amateur Radio license in 1985, primarily to experiment with data communications over VHF/UHF Amateur Radio. At that time, Packet Radio in Amateur Radio was becoming a very big deal; for a time it kind of dominated Amateur Radio.
In very simplistic terms, data communications over Amateur Radio is actually a fluid exchange of bits between four distinct elements:
- The radio - the piece of equipment which takes a baseband input (usually audio) and translating that signal into a radio frequency signal. Typically (but not an absolute given) the radio usually includes the reverse process - receiving a radio frequency signal and translating it into a baseband signal.
- The CODEC or MODEM - as we know them in 2021, radios are usually set up for analog (audio) input and output on the baseband (non-RF) side so you need a device that takes digital data that you want to transmit and codes and decodes that data. That function is sometimes called a CODEC (Coder / Decoder) or a Modem (Modulator / Demodulator).
- The Protocol Engine - The modem just handles the analog to digital to analog chore. The protocol engine is in charge of encoding the bits so they'll survive the rough journey over the air, where there is interference, fading, and other hazards. The protocol engine arranges the bits "around" the actual data. One example is adding a callsign identifier.
- The Applications - I'm vastly simplifying this element but basically once the protocol engine does its job, it hands the data (stripped of all the protocol engine bits) over to the application. One example of an application is email.
I said "fluid exchange" because the needed functionality can drift back and forth between the various elements, depending on who is actually making the elements. For example, the venerable Kenwood TM-D710GA is a pretty capable radio with a built-in modem (1200 and 9600).
Those of us that just want to play with data, like send email over Amateur Radio, would love for all of the above to be packaged up into an inexpensive appliance. Kind of like a laptop with Wi-Fi, only it works over the long(er) distances that we've come to expect with Amateur Radio VHF/UHF communications. And unlike the black box that is Wi-Fi embedded into a laptop, we do want to play at least a little bit.
In 2021, we're not there yet. By mid-decade, we might be if certain technology trends keep going the right way, like the way we keep getting better and better Raspberry Pi computers for the same $35 over the years.
Given the desire for the "data communications over Amateur Radio appliance" described above, I keep hoping. We got close, briefly, a few years ago in the Northwest Digital Radio UDRX-440 project. I told some of the story about why the UDRX-440 didn't quite make it to becoming a finished product in a previous article - Amateur Radio Digital Communications (aka ampr.org / 44net).
The bigger problem than that what the stillbirth of the UDRX-440 represented, is that Amateur Radio is just a maddeningly small market for a manufacturer to actually create, ship, and support a viable product. (Not to mention Amateur Radio being a market that is maddeningly price sensitive.) What we all want to do with our "inexpensive Amateur Radio data communications appliance" varies widely.
Thus, when I've (unwisely) voiced my quest for said appliance over the years to several people that are way smarter than me, they've given me an answer that, at first blush, was irritatingly simplistic:
GNU Radio is the answer... what was the question?
Irritating to me because GNU Radio is simultaneously an incredibly capable software package, and a near-infinite time sink when one (like me) just wants to do data communications (appliance style) and spend most of your time actually communicating data over the air.
Doubly irritating because, in the end, I've come to understand (and admit) that they're right. The fantasy Amateur Radio data communications appliance (such as the UDRX-440) simply isn't a viable product in a market as small and as price sensitive as Amateur Radio. So they're way ahead of me in recommending GNU Radio to me because anything one wants to experiment with in Amateur Radio data communications is probably already in GNU Radio.
So, if GNU Radio is the answer, how do you get started? Fortunately the beauty of GNU Radio, aside from it being open source and constantly improved, is that it's so widely used that it's already been ported to a huge ecosystem of radio hardware.
At the low end, GNU Radio supports the RTL-SDR types of software defined receivers. Advice - don't go any lower-end than buying a genuine RTL-SDR Blog unit for around $25.00 US. Those specific products pack an incredible amount of engineering and customization beyond the very generic, inexpensive RTL-SDR units; less expensive units (though they "work") just aren't worth the headaches, in my opinion.
At the high end "Tesla" class of hardware, GNU Radio supports the Ettus Research (division of National Instruments) Universal Software Radio Peripheral products. They're pricey, but Amateur Radio operators just wanting to experiment with data communications aren't their target customers.
In between those two extremes there are many software defined transceivers, but most of them suffer from various issues such as availability, cost, and manufacturer / community support. Thus I was grateful when a very knowledgeable Amateur Radio friend tipped me off that the Analog Devices ADALM-PLUTO is about the best "starter" Software Defined Transceiver for experimenting with software defined radio (as in the radio frequency hardware) for doing advanced data communications in Amateur Radio.
The ADALM-PLUTO has much to recommend it:
- Capable - RF coverage from 325 MHz to 3.8 GHz, and up to 20 MHz of instantaneous bandwidth, and has separate receive and transmit antenna ports. Regrettably, this precludes the ADADM-PLUTO from being used on the US Amateur Radio 50-54 MHz (6 meters), 144-148 MHz (2 meters), and 219 / 222-225 MHz (1.25 meters) bands.
- Continuously available by a major manufacturer (Analog Devices) and stocked by a major distributor (Digi-Key Electronics)
- Reasonably low cost ($150 at Digi-Key Electronics)
- Software support includes GNU Radio (and by extension, GNU Radio Companion - the graphical front end for GNU Radio)
- It's easy to experiment with in a lab / experiment setting - it's powered and communicated with by USB
The ADALM-PLUTO is likely to remain in production until superseded by a better unit. The ADALM-PLUTO's "mission" is to be an "RF lab in a shirt pocket" for students such as those in electrical engineering programs, and of course it's in Analog Devices' interest to get engineering students familiar with its products and thus the ADALM-PLUTO showcases several of Analog Devices' chips. Thus it's optimized for cost and functionality, not for usability by Amateur Radio operators.
One benefit that the ADALM-PLUTO has over competing software defined transceivers is that for it to be usable by students, it has to be well-documented, and that seems to be the case - see the ADALM-PLUTO Overview page. Upon first connection to a computer, the ADALM-PLUTO enumerates on USB as a drive, with considerable documentation onboard.
The major downside to the ADALM-PLUTO is that the transmit power is very low - 5 dBm which is approximately 3 mW (3 milliwatts, 3/1000 watt). (Remember, it's powered entirely by a USB connection over a micro USB connector.) Given the intended audience and price point of this product, that's to be expected. To get a more reasonable power level, you would have to implement a power amplifier, and it's tough to make a good power amplifier that works over a wide frequency range as the ADALM-PLUTO does.
Thus I'm creating a new reference page - Analog Devices ADALM-PLUTO - Reference to collect all the bits of info that I'll be gathering up about the Analog Devices ADALM-PLUTO. It's a bit sparse as I write this, but it will definitely grow as my learning curve on this looks like a steep cliff at the moment.
One more bit on the quest for an Amateur Radio Data Communication Appliance - while the ADALM-PLUTO will definitely use GNU Radio... it doesn't have to use GNU Radio. IE, you don't have to constantly be in "experimentation" mode with it. Once you have it doing what you want it to be doing, it will keep doing that (IE, appliance mode)... until you decide to change it. Thus, like a lot of other projects, once you have a successful "recipe" for it, you can clone that setup, your friends can benefit from your work, and you can spend your time communicating.
Thanks for reading!
Steve Stroh N8GNJ
Bellingham, Washington, USA
2021-04-15
Copyright © 2021 Steven K. Stroh
New web page - A Brief Survey of Technological Innovation in Amateur Radio
This is a paper I wrote for the ARRL and TAPR Digital Communications Conference 2022.
A Brief Survey of Technological Innovation in Amateur Radio
By Steve Stroh N8GNJ1
ARRL and TAPR 2022 Digital Communications Conference Charlotte, North Carolina, USA 2022-09-16 thru 18
Abstract
In recent decades, the perception of Amateur Radio within the general public has shifted from Amateur Radio being useful, innovative, and an interesting technical activity, to Amateur Radio being perceived as an anachronism and largely irrelevant (except in the direst of communications emergencies). Summarized: “Ham Radio – that’s still around?”
Amateur Radio’s service to the public for emergency communications is being supplanted by improved commercial and government communications capabilities such as improved Iridium2 satellite phones, the FirstNET3 public safety cellular system, and most recently, the nomadic capability of the Starlink4 broadband satellite system.
Amateur Radio has continuously developed unique technological innovations in radio technology, and that has not only continued in the modern era but has accelerated. However, that ongoing, unique contribution to technological society is, increasingly, unrecognized. That is unfortunate. If regulators, lawmakers, industry, the general public... and the Amateur Radio community itself understood the unique contributions to technological innovations in radio technology that Amateur Radio continues to develop, perhaps such recognition might improve Amateur Radio’s perception that it remains a valuable part of society, worthy of continued access to portions of the electromagnetic spectrum.
Keywords
Amateur, Radio, Operator, Ham, Wireless, Technology, Innovation, Spectrum, Digital, VHF, UHF, SHF, Microwave, Communications, ARDC, Techies, Makers, Hackers, Zero Retries Newsletter, Experimentation, Research and Development, FlexRadio, Steve Stroh N8GNJ
Background
For decades, I have been an admirer of technological innovation in Amateur Radio. Not just new technologies like Packet Radio emerging in the 1980s, but new techniques for old problems such as digital techniques enabling reliable communications via unreliable mediums such as the High Frequency (HF)5 (aka Shortwave) portions of the electromagnetic spectrum.
Amateur Radio’s unique culture, the varying characteristics of various portions of spectrum allocated to (or shared with) Amateur Radio operations, and the many highly capable and skilled Amateur Radio Operators, have resulted in a fertile, and welcoming “experimental zone” for technological innovation in radio technologies. Until recent decades, that culture of technological innovation was widely recognized, and encouraged. In the last few decades, the recognition of
1 Email – [email protected]
2 https://www.iridium.com/network/
3 https://firstnet.gov/network
4 https://www.starlink.com/rv
5 https://en.wikipedia.org/wiki/High_frequency
A Brief Survey of Technological Innovation in Amateur Radio
Amateur Radio’s utility and contributions to technological innovation have been deprecated to near irrelevence... at least in popular perception... by ubiquitous Internet access, mobile phones, caricatures of Amateur Radio as “Grandpa sitting in the basement tapping on a Morse Code key”, and most notably, the removal of old barriers to individuals communicating across international borders.
A primary reason that this is a concern for society is that it has become irrevocably dependent on radio technology as the primary method of communications for mobile devices, most notably cellular technology, wireless local area networks (Wi-Fi), and most recently, direct-to-user satellite communications. For many people, their mobile phone is their only method of communications and media consumption. Much of that technology has been developed and manufactured in China. Dependence on China for such a critical infrastructure function is proving to be fraught with peril. To counter that peril, the US and other Western nations must quickly develop additional expertise, and personnel, “in nation” to better develop and support this now-critical wireless infrastructure. Amateur Radio can be a “training ground” for developing familiarity and expertise with radio technology, leading to careers in developing and supporting radio technology... but only if Amateur Radio is recognized as a useful and interesting.
The rise of technology specialists, especially those trained in Information Technology (IT), the “Maker culture”6, and the “Hacking Culture”7 have breathed new life into Amateur Radio. “Techies” have discovered Amateur Radio as an enabling technology for supporting experimentation with Information Technologies (such as building hobbyist / not-for-profit wide- area microwave networks). Makers have discovered that there are incredibly interesting things that they can add to their personal knowledge base and practical projects based on capabilities Amateur Radio has long taken for granted, such as long-range communications via VHF / UHF repeaters. Hackers have discovered Amateur Radio as a fertile “playground” for their experiments and expansion of knowledge about radio technology, such as Software Defined Receivers... and Transmitters (with an Amateur Radio license).
I started the Zero Retries Newsletter8 in July, 2021 out of frustration that the totality of technological innovation in Amateur Radio wasn’t being recognized by the Amateur Radio community, its regulators, and especially the public at large. Specifically, I was worried about the growing public perception that Amateur Radio is irrelevant, or worse, an anachronism. Such a perception, if it is to continue for much longer, may prove catastrophic to Amateur Radio, most notably in the loss of Amateur Radio access to various portions of spectrum. To date I’ve published more than fifty weekly issues of Zero Retries, and each issue highlights some aspect of technological innovation in Amateur Radio.
Literally, Amateur Radio is a license to experiment with radio technology and a welcoming “innovation zone” to develop new and exciting technological innovations in radio technology. I hope to make that point with the vignettes in this paper.
6 https://en.wikipedia.org/wiki/Maker_culture
7 https://en.wikipedia.org/wiki/Hacker_culture
8 https://zeroretries.substack.com (will eventually migrate to https://zeroretries.org)
...
Read the rest of the paper at:
https://www.superpacket.org/n8gnj_dcc_2022_final_for_web.pdf
Posted by Steve Stroh on September 16, 2022 at 06:30 AM in Amateur Radio Future, ARDC, AREDN, ARRL and TAPR DCC, Conferences, D-Star, General Commentary, Growing Amateur Radio, Internet, Microwave, New Packet Radio, Packet Radio, Presentations / Talks, RadioMirror, Radios, Regulatory, Satellite, Software Defined Transceiver, SuperPacket Web Pages, TCP/IP, WSJT Modes | Permalink