A New Digital Mode For Radio Amateurs

There used to be a time when amateur radio was a fairly static pursuit. There was a lot of fascination to be had with building radios, but what you did with them remained constant year on year. Morse code was sent by hand with a key, voice was on FM or SSB with a few old-timers using AM, and you’d hear the warbling tones of RTTY traffic generated by mechanical teletypes.

By contrast the radio amateur of today lives in a fast-paced world of ever-evolving digital modes, in which much of the excitement comes in pushing the boundaries of what is possible when a radio is connected to a computer. A new contender in one part of the hobby has come our way from [Guillaume, F4HDK], in the form of his NPR, or New Packet Radio mode.

NPR is intended to bring high bandwidth IP networking to radio amateurs in the 70 cm band, and it does this rather cleverly with a modem that contains a single-chip FSK transceiver intended for use in licence-free ISM band applications. There is an Ethernet module and an Mbed microcontroller board on a custom PCB, which when assembled produces a few hundred milliwatts of RF that can be fed to an off-the-shelf DMR power amplifier.

Each network is configured around a master node intended to use an omnidirectional antenna, to which individual nodes connect. Time-division multiplexing is enforced by the master so there should be no collisions, and this coupled with the relatively wide radio bandwidth of the ISM transceiver gives the system a high usable data bandwidth.

Whether or not the mode is taken up and becomes a success depends upon the will of individual radio amateurs. But it does hold the interesting feature of relying upon relatively inexpensive parts, so the barrier to entry is lower than it might be otherwise. If you are wondering where you might have seen [F4HDK] before, we’ve previously brought you his FPGA computer.

Bidirectional IP with New Packet Radio

There are a few options if you want to network computers on amateur radio. There are WiFi hacks of sort, and of course there’s always packet radio. New Packet Radio, a project from [f4hdk] that’s now on hackaday.io, is unlike anything we’ve seen before. It’s a modem that’s ready to go, uses standard 433 ISM band chips, should only cost $80 to build, and it supports bidirectional IP traffic.

The introductory documentation for this project (PDF) lays out the use case, protocol, and hardware for NPR. It’s based on chips designed for the 433MHz ISM band, specifically the SI4463 ISM band radio from Silicon Labs. Off the shelf amplifiers are used, and the rest of the modem consists of an Mbed Nucleo and a Wiznet W5500 Ethernet module. There is one single modem type for masters and clients. The network is designed so that a master serves as a bridge between Hamnet, a high-speed mesh network that can connect to the wider Internet. This master connects to up to seven clients simultaneously. Alternatively, there is a point-to-point configuration that allows two clients to connect to each other at about 200 kbps.

Being a 434 MHz device, this just isn’t going to fly in the US, but the relevant chip will work with the 915 MHz ISM band. This is a great solution to IP over radio, and like a number of popular amateur radio projects, it started with the hardware hackers first.

Es’hail-2: Hams Get Their First Geosynchronous Repeater

In the radio business, getting the high ground is key to covering as much territory from as few installations as possible. Anything that has a high profile, from a big municipal water tank to a roadside billboard to a remote hilltop, will likely be bristling with antennas, and different services compete for the best spots to locate their antennas. Amateur radio clubs will be there too, looking for space to locate their repeaters, which allow hams to use low-power mobile and handheld radios to make contact over a vastly greater range than they could otherwise.

Now some hams have claimed the highest of high ground for their repeater: space. For the first time, an amateur radio repeater has gone to space aboard a geosynchronous satellite, giving hams the ability to link up over a third of the globe. It’s a huge development, and while it takes some effort to use this new space-based radio, it’s a game changer in the amateur radio community.

Friends in High Places

The new satellite, Es’hail-2, was built for Es’hailSat, a Qatari telecommunications concern. As satellites go, it’s a pretty standard machine, built primarily to provide direct digital TV service to the Middle East and Africa. But interestingly, it was designed from the start to carry an amateur radio payload. The request for proposals (RFP) that Es’hailSat sent to potential vendors in early 2014 specifically called for the inclusion of an amateur repeater, to be developed jointly by AMSAT, the Radio Amateur Satellite Corporation.

The other kind of networking. His Excellency Al-Attiyah (A71AU). Source: Al-Attiyah International Foundation for Energy and Sustainable Development

The repeater aboard Es’hail-2 was developed as a joint effort between the Qatar Amateur Radio Society (QARS), Es’HailSat, and AMSAT-DL, the AMSAT group in Germany. The willingness of Es’HailSat to include an amateur radio payload on a commercial bird might be partially explained by the fact that the QARS chairman is His Excellency Abdullah bin Hamad Al Attiyah (A71AU), former Deputy Prime Minister of Qatar.

The repeater was engineered with two main services in mind. The first is a narrowband transponder intended for phone (voice) contacts, continuous wave (CW) for Morse contacts, and some of the narrow bandwidth digital modes, like PSK-31. The other transponder is for wideband use, intended to test Digital Amateur Television (DATV). The wideband transponder can carry two simultaneous HD signals and a beacon broadcasting video content from QARS. Both transponders uplink on the portion of the 2.4-GHz reserved for hams, while downlinking on the 10.4-GHz band.

Es’hail-2 was launched aboard a SpaceX Falcon 9 from Cape Canaveral on November 15, 2018. The satellite was boosted to a geosynchronous orbit in the crowded slot located at 26.5° East longitude, parking it directly above the Democratic Republic of Congo. After tests were completed, a ceremony inaugurating the satellite as “Qatar OSCAR-100”, or QO-100, was held on February 14, 2019, making it the 100th OSCAR satellite launched by amateurs.

Listening In

Sadly for hams in the Americas and most of eastern Asia, QO-100 is out of range. But for hams anywhere from coastal Brazil to Thailand, the satellite is visible 24 hours a day. The equipment to use it can be a bit daunting, if the experience of this amateur radio club in Norway is any indication. They used a 3-meter dish for the 2.4-GHz uplink, along with a string of homebrew hardware and a lot of determination to pull off their one contact so far, and this from a team used to bouncing signals off the Moon.

Receiving signals from QO-100 is considerably easier. A dish in the 60-cm to 1-meter range will suffice, depending on location, with a decent LNB downconverter. Pretty much any SDR will do for a receiver. An alternative to assembling the hardware yourself — and the only way to get in on the fun for the two-thirds of the planet not covered by the satellite — would be to tune into one of the WebSDR ground stations that have been set up. The British Amateur Television Club and AMSAT-UK, located at the Goonhilly Earth Station, have set up an SDR for the narrowband transponder that you can control over the web. I used it to listen in on a number of contacts between hams the other night.

It’s hard to overstate the importance of QO-100. It’s the first ham repeater in geosynchronous orbit, as well as the first DATV transponder in space. It’s quite an achievement, and the skills it will allow hams to develop as they work this bird will inform the design of the next generation of ham satellites. Hats off to everyone who was involved in getting QO-100 flying!

Weeknummering GPS gereset

GPS-tijd gereset

Op 6 april om middernacht wordt het weeknummer van de GPS-tijd gereset. Hierdoor kan apparatuur die gebruik maakt van het GPS-systeem mogelijk niet meer goed functioneren. Controleer daarom of bijvoorbeeld uw navigatiesysteem op 7 april nog goed werkt.

Achtergrond GPS-tijd

De GPS-tijd wordt afgeleid uit twee tellers, de seconden- en de weekteller. De secondenteller houdt het aantal seconden bij sinds de start van de week. Een week begint daarbij om middernacht in de nacht van zaterdag op zondag. Daarnaast is er de weekteller. Deze teller houdt simpelweg bij hoeveel weken er zijn verlopen sinds de start van de telling. Beide tellers zijn gestart om middernacht op 5 januari 1980. Vanwege het simpele feit dat de weekteller wordt bijgehouden in een getal van 10 bits, kan slechts tot 1023 geteld worden. Daarna springt te weekteller weer op 0 (een reset). Dat gebeurt dus op 6 april om middernacht.

De meeste moderne apparatuur heeft geen last van deze reset. Raadpleeg bij twijfel de website van de fabrikant van uw apparatuur. Mogelijk is er een software-update nodig.

The $50 Ham: Getting Your Ticket Punched

Today we start a new series dedicated to amateur radio for cheapskates. Ham radio has a reputation as a “rich old guy” hobby, a reputation that it probably deserves to some degree. Pick up a glossy catalog from DX Engineering or cruise their website, and you’ll see that getting into the latest and greatest gear is not an exercise for the financially challenged. And thus the image persists of the recent retiree, long past the expense and time required to raise a family and suddenly with time on his hands, gleefully adding just one more piece of expensive gear to an already well-appointed ham shack to “chew the rag” with his “OMs”.

Not a $50 ham. W9EVT’s shack. Source: QRZ.com

As I pointed out a few years back in “My Beef With Ham Radio”, I’m an inactive ham. My main reason for not practicing is that I’m not a fan of talking to strangers, but there’s a financial component to my reticence as well – it’s hard to spend a lot of money on gear when you don’t have a lot to talk about. I suspect that there are a lot of would-be hams out there who are turned off from the hobby by its perceived expense, and perhaps a few like me who are on the mic-shy side.

This series is aimed at dispelling the myth that one needs buckets of money to be a ham, and that jawboning is the only thing one does on the air. Each installment will feature a project that will move you further along your ham journey that can be completed for no more than $50 or so. Wherever possible, I’ll be building the project or testing the activity myself so I can pursue my own goal of actually using my license for a change.

(A shout-out to Robert for suggesting this series, and for graciously allowing me to run with his idea.)

Getting Your Ticket

The licensing of amateur radio stations in the United States goes all the way back to 1912. (I’m concentrating on US laws and customs regarding the amateur radio service simply because that’s where I live; please feel free to chip in on the comments section about differences in other countries.) Anyone who wants to operate on the bands reserved for the amateur radio service has to be licensed by the Federal Communication Commission. Unlicensed individuals are free – and encouraged – to listen in on the bands, but if you don’t have a license, you can’t transmit. And trust me, the local hams, with know-how, equipment, and all the time in the world, will find you, resulting in an unpleasant encounter with the FCC.

There’s really no reason not to get a license anyway. This will be among the cheapest parts of a ham’s journey, and perhaps even free. To earn a license you’ll need to pass a written exam, but before taking the plunge you’ll need to know a little about the classes of amateur radio licenses, and the privileges they bestow.

The current entry-level license class in the US is called Technician class; the old Novice class was eliminated in 2000, along with the Morse code requirement for all classes. Technicians have privileges to operate mainly on the upper frequencies, primarily on the 2-meter (144 MHz) and 70-cm (420 MHz) bands in phone mode, which means voice transmissions. Technicians also have access to small slices of the 10-meter band using data modes, and small sections of 15-, 40-, and 80-meters if they learn Morse or use a computer to send and receive it. This limits the Technician to mainly local communications, but there’s plenty to do and loads to learn on these bands.

The band plan for US hams. Note that Technicians only have phone (voice) privileges on 10 meters and below; the long haul bands are off limits unless you use Morse. Source: ARRL.org

Practice, Practice, Practice

Even with all the limitations, a Technician license still offers access to a lot of spectrum and serves as the gateway to the next two classes, General and Extra. Everyone has to start with a Technician license, which requires passing a 35-question multiple choice examination. The exam is standardized with questions selected from a fixed pool, with topics ranging from knowing FCC Part 97 rules to basic electronics and RF theory. The exam is pretty easy, especially for anyone with a background in electronics. In fact, many complete newbies come to exam sessions after having run through enough online practice tests to see every possible pool question and pass the exam without understanding a thing about radios or electronics. There are lively debates over whether that’s a good thing or not – personally, I’m not a fan of it – but it is what it is; the Technician exam is dead easy.

Your investment in a Technician license will be minimal, and mostly consists of the time it takes to study. Online practice tests – I recommend the tests on QRZ.com – are free to take as many times as you need to. Some ham clubs offer local classes aimed at helping you to prepare, and those generally charge only a nominal fee. There are even one-day intensive “ham cram” sessions where you’re guided through all the material and take the exam at the end of the day.

Typical exam session. Calculators are allowed, but no smartphones, please. Source: Tri-County Amateur Radio Club

Exam sessions are run by Volunteer Exam Coordinators (VECs) Volunteer Examiners (VEs), hams who have special training in administering and grading exams. They too charge only a nominal fee – I think I paid $15 – and may even waive the fee under certain circumstances. There are also occasional special events like the annual Field Day, where hams set up tents and booths in public places as an outreach to the public, where exams are often administered for free.

Honestly, getting your Technician license is about as low impact as the amateur radio hobby gets. Once you can consistently pass practice tests online, the actual exam is a breeze. Exams are graded on the spot so you’ll know instantly how you did, and you can even take the next exam for no extra charge if you’re ready. Give it a shot even if you haven’t studied – I nearly passed my Extra exam going in cold after I aced my General.

Next Time

In the next installment I’ll start discussing what the newly minted Technician can do with his or her license. It may seem like a pipe dream to get on the air for less than $50, but it’s surprising what’s available these days, and you’ll find that fifty dollars can go a long way toward making your first contact.

This SDR Uses A Tube

When you think of a software defined radio (SDR) setup, maybe you imagine an IC or two, maybe feeding a computer. You probably don’t think of a vacuum tube. [Mirko Pavleski] built a one-tube shortwave SDR using some instructions from [Burkhard Kainka] which are in German, but Google Translate is good enough if you want to duplicate his feat. You can see a video of [Mirko’s] creation, below.

The build was an experiment to see if a tube receiver could be stable enough to receive digital shortwave radio broadcasts. To avoid AC line hum, the radio is battery operated and while the original uses an EL95 tube, [Mirko] used an EF80.

To get the necessary stability, it is important that everything is secured. The original build made sure the tube would not move during operation, although [Mirko’s] tube mounting looks more conventional but still quite secure. Loose coupling of the antenna also contributes to stability, and the tuning adjustments ought to have longer shafts to minimize hand capacitance near the tuning knob. Another builder [Karl Schwab] notes that only about 1/3 of the tuning range is usable, so a reduction gear on the capacitor would also be welcome.

The tube acts as both an oscillator and mixer, so the receiver is a type of direct conversion receiver. The tube’s filament draws about 200 mA, so battery operation is feasible.

According to [Burkhard] his build drifts less than 1 Hz per minute, which isn’t bad. As you can see in the video, it works well enough. The EF80, by the way, is essentially an EF50 with a different base — that tube helped win World War II. If you like to build everything, maybe you could try the same feat with a homemade tube.

PI2NOS stopt in zijn huidige vorm

Zendmast Lopik

De bovenregionale repeater PI2NOS wordt ontmanteld. Dat meldt de Stichting Scoop Hobbyfonds op haar website. Vorige week stopte de ontvanger in Breda. De komende weken volgen een aantal locaties in het noorden van het land.

Drie redenen

De stichting noemt drie redenen waarom PI2NOS in zijn huidige vorm moet stoppen.

De eerste en belangrijkste reden is dat de inkomsten van sponsoren en donateurs teruglopen. Ten tweede heeft de bovenregionale repeater al lange tijd te kampen met frequentiemisbruik. Sommige mensen verstoren het verkeer op de PI2NOS zodanig dat goedwillenden afscheid nemen van de repeater. Ondanks extra inspanningen van het Agentschap Telecom zijn de verstoringen niet gestopt. Tot slot noemt de stichting als reden dat de kosten van de verschillende opstellocaties voor hun systemen oplopen.

Het is jammer dat dit unieke project van gekoppelde radiosystemen in zijn huidige vorm niet kan blijven bestaan.

EF50: the Tube that Changed Everything

From today’s perspective, vacuum tubes are pretty low tech. But for a while they were the pinnacle of high tech, and heavy research followed the promise shown by early vacuum tubes in transmission and computing. Indeed, as time progressed, tubes became very sophisticated and difficult to manufacture. After all, they were as ubiquitous as ICs are today, so it is hardly surprising that they got a lot of R&D.

Prior to 1938, for example, tubes were built as if they were light bulbs. As the demands on them grew more sophisticated, the traditional light bulb design wasn’t sufficient. For one, the wire leads’ parasitic inductance and capacitance would limit the use of the tube in high-frequency applications. Even the time it took electrons to get from one part of the tube to another was a bottleneck.

There were several attempts to speed tubes up, including RCA’s acorn tubes, lighthouse tubes, and Telefunken’s Stahlröhre designs. These generally tried to keep leads short and tubes small. The Philips company started attacking the problem in 1934 because they were anticipating demand for television receivers that would operate at higher frequencies.

Dr. Hans Jonker was the primary developer of the proposed solution and published his design in an internal technical note describing an all-glass tube that was easier to manufacture than other solutions. Now all they needed was an actual application. While they initially thought the killer app would be television, the E50 would end up helping the Allies win the war.

Television

In Britain, there was a single television transmitter at Alexandra Palace — the start of what would become the BBC. This was not only the first public television service but also the first fully electronic television system. Pye Ltd. — a company eventually bought by Philips — made receivers that were surprisingly successful. The sound was at 41.5 Mhz and the visual was at 45 MHz — high frequencies for those days.

Spurred by the demand, Pye decided that a set with more range would create a broader market for receivers. The problem was finding a tube that could handle the 45 MHz frequency in their tuned radio frequency (TRF) design.

Pye wrote out the specifications for what they needed, but couldn’t get them made reliably and cheaply. They turned to Philips who took Jonker’s ideas and added some items needed for this application, producing the EF50 — a pentode. The resulting TV set (see page 199) had a range of about five times the older sets.

Construction

Old tubes used a difficult process called pinching to seal the end of a glass tube with the leads running through it. The pinch formed an inverted V shape where the bakelite base of the tube fit the wide part of the V and the wires within entered the tube through the point of the V.

This had several problems. As more wires had to pass through the pinch, they had to get closer together. That increased stray capacitance. Worse, the distance from the bottom of the V to the top of the V meant wires had to be relatively long which added inductance. Finally, the size of the V — often half the total length of the tube — was preventing tubes from getting smaller, hindering the development of portable equipment.

One way to solve this was to build the tubes from metal instead of glass, with some connections going through the top of the tube. However, these tubes were expensive to manufacture in quantity and designers did not like having to wire to the top of the tube. The Stahlröhre bucked the trend, putting the tube components in horizontally to decrease wiring to the base and using no top connections. However, again, the cost to manufacture was high. The 1934 acorn tube was all glass and used two parts sealed together with short leads but were also known to be expensive to produce.

Philips, Pye, and the War

When the Dutch military first asked Philips for tubes around 1918, they declined; Gerard Philips though radio had little practical value. It would be 1923 before Philips decided to use its expertise in light bulbs to produce radio tubes. By 1938, Jonker’s work was circulating and in 1939 there was even an article about it in Wireless Engineer.

By the time Pye came looking for high-frequency tubes, Philips was ready due to the earlier work. The Pye receiver used six tubes and required some tweaking, including the addition of a metal shield.

Meanwhile, there was war. The Battle of Britain was in 1940 and the military was busy in 1939 working on RADAR that also operated at high frequencies. This RADAR — and the command and control strategies used with it — would be key to winning the upcoming battle. The team working on airborne RADAR apparently only had one receiver good enough to get results. Then they received a tip that Pye had an excellent receiver that worked in the same frequency range. This became the basis for Britain’s RADAR sets through the war. About 60% of all Pye TV IF strips wound up in British RADAR sets.

The big problem was that by 1940 the Netherlands was in German hands. The production line needed to be moved to Britain, and when the HMS Windsor took the escaping Dutch government to England, the Philips family was also onboard with the diamond dies needed to produce the fine tungsten wires used in the EF50 tube.

After the war, the EF50 would find a home in many oscilloscopes and radio receivers. This was both because of its superior frequency ability and the availability of war surplus. Others would also produce the tube including Marconi-Osram (as the Z90) and Cossor (63SPT). Mullard produced the tube using the original Phillips equipment and both Rogers and Sylvania also produced a version.

Nuvistors

This type of tube would be the king of the hill for RF work until 1959. That’s the year RCA introduced the nuvistor — a metal and ceramic tube assembled in a vacuum chamber. These were nearly as tiny as a transistor, low noise, and had excellent performance at radio frequencies. These were found in a lot of gear all the way until the early 1970s including TV tuners, oscilloscopes, and tape recorders.

More Details

There’s a very long and very well-researched history of everyone and everything related to the EF50 if you want to really dig into the details. There’s even a translation of part of the original internal report about it. You can also find similar information and a lot of unique pictures at [Keith Thrower’s] site.

If you like the sound of an old tube radio, the medium wave receiver in the video below uses some EF50s and it sounds great. Want more tube history? Or perhaps you’d rather make your own. Or you can watch how they made similar tubes back in the day.