This article is broken into two parts. First comes the “Oscar” preselector/preamplifier. As I said, I intended it to be either part of the overall receiver or used as a standalone where desired. The second part deals with the WBR upgrades. Both designs were built using the same techniques and I’ve tested both and found that—especially in concert—they do about as well as some of my boat anchors! So if your soldering iron is ready, I’ll start by describing “Oscar.”
A frequent complaint you will hear about amateur radio is that it is a chequebook pursuit. Of course you can work the incredible DX if you spend $20k on a high-end radio, big antenna, and associated components. The reality is though that because it’s such a multi-faceted world there are many ways into it of which the operator with the shiny rig is taking only one.
On the commonly used HF and VHF bands at the lower end of the radio spectrum you will definitely find chequebook amateurs of the type described in the previous paragraph. But as you ascend into the microwave bands there are no shiny new radios on the market, so even the well-heeled licensee must plow their own furrow and build their own station.
You might think that this would remain a chequebook operation of a different type, as exotic microwave devices are not always cheap. But in fact these bands have a long history of extremely inexpensive construction, in which skilled design and construction as well as clever re-use of components from satellite TV systems and Doppler radar modules play a part. And it is a project following this path that is our subject today, for [Peter Knol, PA1SDB] has repurposed a modern Doppler radar module as a transmitter for the 10GHz or 3cm amateur band (Google Translate version of Dutch original). The best bit about [Peter]’s project is the price: these modules can be had for only three Euros.
Years ago a Doppler module would have used a Gunn diode in a waveguide cavity and small horn, usually with an adjacent mixer diode for receiving. Its modern equivalent uses a transistor oscillator on a PCB, with a dielectric resonator and a set of patch antennas. There is also a simple receiver on board, but since [Peter] is using a converted ten-Euro satellite LNB for that task, it is redundant.
He takes us through the process of adjusting the module’s frequency before showing us how to mount it at the prime focus of a parabolic antenna. FM modulation comes via a very old-fashioned transformer in the power feed. He then looks at fitting an SMA connector and using it for more advanced antenna set-ups, before experimenting with the attenuating properties of different substances. All in all this is a fascinating read if you are interested in simple microwave construction.
The result is not the most accomplished 10 GHz station in the world, but it performs adequately for its extremely low price given that he’s logged a 32 km contact with it.
Though we cover our fair share of amateur radio stories here at Hackaday it’s fair to say we haven’t seen many in the microwave bands. If however you think we’ve been remiss in this area, may we point you to our recent coverage of a microwave radio receiver made from diamond?
My amateur radio journey began back in the mid-1970s. I was about 12 at the time, with an interest in electronics that baffled my parents. With little to guide me and fear for my life as I routinely explored the innards of the TVs and radios in the house, they turned to the kindly older gentleman across the street from us, Mr. Brown. He had the traditional calling card of the suburban ham — a gigantic beam antenna on a 60′ mast in the backyard – so they figured he could act as a mentor to me.
Mr. Brown taught me a lot about electronics, and very nearly got me far enough along to take the test for my Novice class license. But I lost interest, probably because I was an adolescent male and didn’t figure a ham ticket would improve my chances with the young ladies. My ham ambitions remained well below the surface as life happened over the next 40 or so years. But as my circumstances changed, the idea of working the airwaves resurfaced, and in 2015 I finally took the plunge and earned my General class license.
The next part of my ham story is all-too-familiar these days: I haven’t done a damn thing with my license. Oh, sure, I bought a couple of Baofeng and Wouxun handy-talkies and lurked on the local repeaters. I even bought a good, solid HF rig and built some antennas, but I’ve made a grand total of one QSO — a brief chat with a ham in Texas from my old home in Connecticut on the 10-meter band. That’s it.
Obviously, there’s a problem. It’s not lack of understanding the art and science of amateur radio. More so than the average Joe who comes in off the street to sit for a license test (and there are far more of those folks than you might think), I have a pretty good grasp of the theory and practice of RF communications. It’s not a money problem, either. At least for now I have enough disposable income to spend on “The World’s Greatest Hobby.” It’s not time either, at least not really. My kids are old enough now to be self-reliant, so it’s not like I’d be working the bands while there are dirty diapers to deal with. And my wife is supportive too, so it’s not that either. So what’s my problem? Why am I not active on the HF bands and checking in on the local repeaters?
Because as it turns out, when you’re a ham you end up talking to other hams. And I don’t like talking to hams.
Lest this be construed as ham-hate, it’s not. Truth be told, I don’t really want to talk to anyone, face to face or over the air. But there’s really something off-putting about the ham style of communication, at least to my ears. Part of this is due to listening to public service radio all my life. My dad was a cop, and hearing dispatches on the radio in his cruiser was the soundtrack of my life from the day I was born. I later listened to scanners as a civilian hobbyist, then with a more professional interest as an EMT and volunteer firefighter. I even worked the other side of the mic as a dispatcher for multiple agencies. So I developed a strong preference in radio style — brief, clipped messages that minimize time on the air while maximizing information content.
In other words, the exact opposite of what hams do.
When I hear two hams chewing the rag, I find myself thinking, “Please, just stop talking and take your thumb off the mic switch.” It’s not so much what they’re talking about, although that certainly plays into it; lots of recounting what the “XYL” made for dinner and updates on everyone’s prostate woes. I could overlook the content choice if someone, somewhere would just unkey the mic once in while and take a breath.
I know, I know — that’s not what ham radio is for. The ham bands are for conversation more than anything else, at least from the sound of it. I think I might have a better experience if I explore the HF nets that meet regularly in preparation for providing emergency communications in disasters; they might be more my style. Or perhaps the digital modes would suit me better – being able to type brief, content-rich messages and make contacts without any of that pesky talking sounds pretty keen to me.
But as it stands, I’m pretty sure I won’t be hanging around the local 2-meter repeater to make sure everyone knows what I’m getting at the grocery store. I’m glad the local hams have built out the infrastructure to do so, and I’m heartened to know they’re practicing the craft. I just don’t want to talk to them that much.
So, active hams, what part of the craft to you find engaging? I’d love to hear your suggestions for ways I, or anyone else, can make greater use of the license and help keep the hobby fun for new and old hams alike.
Any amateur radio operator who is living under a homeowner’s association, covenant, or has any other deed restriction on their property has a problem: antennas are ugly, and most HOAs outright ban everything from 2-meter whips to unobtrusive J-pole antennas.
Earlier this year, the ARRL got behind a piece of legislation called the Amateur Radio Parity Act. This proposed law would amend FCC’s Part 97 rules for amateur stations and direct, ‘Community associations to… permit the installation and maintenance of effective outdoor Amateur Radio antennas.’ This bill passed the US House without objection last September.
Last week, the Amateur Radio Parity Act died in the US Senate. Sen. Bill Nelson (D-FL), the ranking member of the Senate committee on Commerce, Science, and Transportation, refused to move the bill forward in the Senate. The ARRL has been in near constant contact with Senator Nelson’s office, but time simply ran out before the end of the 114th Congress. The legislation will be reintroduced into the 115th Congress next year.
Regular Hackaday readers will be familiar with our convention of putting the name, nickname, or handle of a person in square brackets. We do this to avoid ambiguity as sometimes names and particularly nicknames can take unfamiliar forms that might be confused with other entities referred to in the text. So for example you might see them around [Bart Simpson], or [El Barto]. and occasionally within those brackets you’ll also see a capitalised string of letters and numbers after a name. For example the electronic music pioneer [Bob Moog, K2AMH], which most of you will recognise as an amateur radio callsign.
Every licenced radio amateur is issued one by their country’s radio authority as a unique identifier, think of it as similar to a car licence plate. From within the amateur radio bubble those letters and numbers can convey a significant amount of information about where in the world its user is located, when they received their licence, and even what type of licence they hold, but to outsiders they remain a mysterious and seemingly random string. We’ll now attempt to shed some light on that information, so you too can look at a callsign in a Hackaday piece or anywhere else and have some idea as to its meaning.
Happily for the would-be callsign spotter, there is an internationally agreed format for amateur radio callsigns. It does have occasional edge cases and exceptions, but the chances of encountering them is slim. There will always be a prefix of up to three alphanumeric characters which identifies a country or territory, followed by a single digit, and then followed by up to four characters.
Returning to [Bob Moog]’s callsign [K2AMH] above as a straightforward example, the “K” is one of the prefix letters A, N, K, and W so far used in the ranges assigned to the USA, the “2” indicates that the callsign was issued in New York or New Jersey because the digit in a US callsign represents a region, and the “AMH” is a sequentially issued string of letters acting as a personal identifier. In more recently issued callsigns this will often be a vanity string, perhaps the operator’s initials or similar.
A seasoned callsign-spotter would also be able to tell you that [Bob Moog]’s callsign originates from sometime in the 1950s, as that was the period in which they started issuing single-letter “K” callsigns, and that it denotes a full or advanced class licence because the “K” is not accompanied by another letter. The FCC provide a handy guide to the callsigns they currently issue, if you are curious.
[Bob Moog] provides us with our straightforward example above, but as is so often the case there are many exceptions and international differences that mean not all callsign components have the same interpretation. For example in British callsigns the number does not represent a region, instead for the vast majority it conveys the age of the callsign and the class of licence for which it was issued. If you are digging that deep into the information contained within a callsign issued in another territory, you will often have to resort to your favourite search engine.
Sometimes you will see extra letters with a slash at the start and end of a callsign. Letters at the start mean that the station is operating in another country or territory, for example. Reciprocal agreements exist between countries allowing foreign amateurs to operate within their borders, when doing so they prepend the appropriate international prefix to their own callsign with a slash to indicate the true location of their station. Our example in the image to the left shows a Canadian station working this way in Kuwait.
Of course, not all radio amateurs work from home. There is a long tradition of portable operation, in cars, on foot, in boats, and even in the air. When operating in this manner there is a requirement to indicate this by adding a slash and an appropriate suffix on the end of the callsign. Thus you’ll see “/P” for portable or on foot, “/M” for mobile, and even occasionally “/MM” for maritime mobile and “/AM” for aeronautical mobile. There are tales for example of people working [King Hussein] of Jordan as [JY1/AM] from his royal jet somewhere over the Atlantic on the way to the USA. Incidentally that Jordanian callsign is one of those rare edge cases we mentioned earlier, it has no letters following its number. When you are king, the ultimate in vanity callsigns can be yours!
There is sometimes an undesirable side to being able to extract so much information from a callsign. People will always find an excuse to impose a hierarchy on any group, and radio amateurs are no exception. Thus you will sometimes find holders of older or more advanced licences excluding or being unpleasant to people whose callsigns they deem to be inferior to their own. We recently heard an oldtimer whose callsign reveals he was probably first licenced in the 1950s or 1960s rip into a recently licenced novice with a British M6 callsign, and it was not a particularly pleasant experience. We’re sure Hackaday readers will agree that it doesn’t matter when you were first licenced or what level of radio examination you have passed. You are only as good as the last piece of radio equipment you built, and the last station you worked with it.
Listen to the amateur radio bands long enough, and you’ll likely come to the conclusion that hams never stop talking. Of course it only seems that way, and the duty cycle for a transmitter operating in one of the voice modes is likely to be pretty low. But digital modes can up the duty cycle and really stress the finals on a rig, so this field-expedient heat sink for a ham transceiver is a handy trick to keep in mind.
This hacklet comes by way of [Kevin Loughin (KB9RLW)], who is trying to use his “shack-in-a-box” Yaesu FT-817 for digital modes like PSK31. Digital modes essentially turn the transceiver into a low-baud modem and thus messages can take a long time to send. This poses a problem for the 5-watt FT-817, which was designed for portable operations and doesn’t have the cooling fans and heavy heatsinks that a big base station rig does. [Kevin] found that an old 486 CPU heatsink clamped to a lug on the rear panel added enough thermal mass to keep the finals much cooler, even with a four-minute dead key into a dummy load at the radio’s full 5-watt output.
You may scoff at the simplicity of this solution, and we’ll concede that it’s far from an epic hack. But sometimes it’s the simple fixes that it pays to keep in mind. However, if your project needs a little less seat-of-the-pants and a little more engineering, be sure to check out [Bil Herd]’s primer on thermal management.
One facet of the diverse pursuit that is amateur radio involves the use of amateur radio satellites. These have a long history stretching back to the years shortly after the first space launches, and have been launched as “piggy-back” craft using spare capacity on government and commercial launches.
Though a diverse range of payloads have been carried by these satellites over the years, the majority of amateur radio satellites have featured transponders working in the VHF and UHF spectrum. Most often their links have used the 2m (144 MHz) and 70cm (430MHz) bands. A few have had downlinks in the 10m (28MHz) band, but this has been as far as they have ventured into the HF spectrum.
A new cubesat designed and built by trainees at the US Naval Academy promises to change all that, because it will feature an all-HF transponder with a 15m (21MHz) uplink and a 10m downlink. To that end it will carry a full size 10m wire dipole antenna. The 30KHz wide transponder is an inverting design intended to cancel out the effects of Doppler shift. In their write-up they provide a fascinating description of many aspects of cubesat design, one which should be of significant interest beyond the world of amateur radio.
Whether it’s trying to make contacts across the planet with a transmitter that would have a hard time lighting an LED, or blasting signals into space and bouncing them off the moon, amateur radio operators have always been on the forefront of communications technology. As mankind took to space in the 1950s and 1960s, hams went along for the ride with the first private satellites. But as successful as the OSCAR satellites were, they were still at best only beacons or repeaters in space. What was needed was the human touch – a real live operator making contacts with people on the ground, showing the capabilities of amateur radio while generating public interest in the space program. What was needed was a ham in space.
If at First You Don’t Succeed…
The first attempt to get an amateur radio station into space with a licensed operator started in the waning days of the Apollo era. Owen Garriott (W5LFL) had a Ph.D. in electrical engineering at the time he was selected as one of the first six scientist-astronauts in 1965. He trained for and eventually flew on Skylab 3 in 1973. Late in the run-up to his mission, Garriott made a formal proposal to take along a ham rig so he could make contacts from orbit. NASA liked the idea, but because the idea came up so late in the mission cycle, there was no time to get the gear properly certified for spaceflight and the proposal was rejected.
Fortunately, Garriott would have another mission and another chance to become the first ham in space. Garriott was selected as a mission specialist for STS-9, the Spacelab-1 mission that flew on shuttle Columbia in 1983. Properly prepared this time, Garriott went aloft with a Motorola MX-300 handheld transceiver for the 2-meter band. The antenna was a bit of a compromise; no provision had been made on the Shuttle for an external antenna, so a cavity antenna was mounted to one of the windows with Velcro. The lucky ham to log the first contact (QSO) with an astronaut in orbit was Lance Collister (WA1JXN) of Montana.
The 300 or so QSOs Garriott logged during STS-9 – including VIPs such as US Senator Barry Goldwater (K7UGA) and King Hussein of Jordan (JY1) – were a public relations coup for NASA. Talking directly to someone in orbit had once been a privilege reserved for other astronauts and presidents. Now, any ham could make contact with an astronaut, and what’s more, any ham could use his or her gear and expertise to let school children talk to astronauts.
Inspiring the Next Generation
Recognizing a good thing when they saw it, NASA formalized ham radio in space with SAREX, the Space Amateur Radio Experiment. In cooperation with the Radio Amateur Satellite Corporation (AMSAT) and the American Radio Relay League (ARRL), and with the express intention of getting young people excited about careers in science and engineering, SAREX flew on 25 Shuttle missions from 1983 to 1999.
As the SAREX program progressed, the amateur radio gear flown with missions got more and more complex – slow-scan television (SSTV), an automated packet radio system to enable around the clock QSOs even when the station could not be manned, and expansion from the original 2-meter band to the 70-centimeter UHF band. On the ground, build-out of a telebridge system increased the number of schools that could make contact with the Shuttle by providing a telephone link to fixed ground stations.
Short-duration Shuttle missions weren’t the only flights with hams aboard. In 1988, the Russian Mir space station crew, Vladimir Titov, Musa Manarov, and Valery Polyakov earned their amateur licenses while in orbit. Pulling the enviable callsigns U1MIR, U2MIR, and U3MIR, they were later supplied with a Yaesu FT290 2-meter transceiver and an antenna, which was mounted to a handrail during a spacewalk. Hams aboard Mir continued the outreach to schools over the years as equipment was upgraded and crews changed.
By the time the first components of the ISS started going into orbit in 1998, a ham radio presence was already planned. ARISS, the Amateur Radio on the International Space Station program, brought together amateur radio groups from around the world to work on a comprehensive plan for ham radio stations on the ISS. An Ericsson handheld 2-meter rig was among the first payloads sent up to the Russian Zarya module in 1998, underscoring how integral ham radio had become to the spacefaring nations and their efforts to reach out to the public.
Radios for the ISS
On Earth, getting on the air as a ham is pretty easy – study a bit, pass the test, and buy your first rig. Gear selection amounts to what you can afford and what bands and modes you want to use. But when your rig is headed 400 km upstairs to a pressurized tinfoil tube, the gear selection process has to be a bit more stringent. You might think this means the gear is completely custom-built by some government contractor, but as it turns out, pretty much all of the radios flying on the ISS right now are off-the-shelf gear that any ham can buy and operate. Like any other equipment headed to the ISS, ham radio gear has to be flight qualified to make sure it doesn’t pose any hazard to the station or crew, but other than that all the rigs up there today would be familiar to any ham.
There are currently three stations flying aboard the ISS in three different modules. Along with the original Ericsson 2-meter handheld transceiver and packet modem in the Zarya module, there are Kenwood dual-band (VHF and UHF) radios in the Zvezda service module near the dining table, and another station in the Columbus module.
The Ericsson MP-A VHF rig in Columbus has a reputation for ruggedness and reliability, but after 16 years of operation aboard the ISS the radio recently started showing error codes and is currently off the air. ARISS operations were transferred to the station in the Russian modules until a replacement station can be sent up. ARISS already had plans to fly a Kenwood D710-GA and power supply, both of which are undergoing final approval and certification by NASA before going topside.
Any ham will tell you that half of the art of amateur radio lies in antenna design and construction. Earthbound hams have a lot of freedom to experiment with antennas and run feedlines through open windows, but things are a bit more constrained for their ISS counterparts.
While the antennas on the early Shuttle missions were somewhat ad hoc, the ISS was designed from the get-go to support multiple external antennas for ARISS operations. Early ISS crews installed four antenna systems around the service module. Designated WA1 to WA4, each antenna consists of Kapton-coated whips for either UHF/VHF or HF signals along with a spiral antenna for the L-band (1-2GHz) and S-band (2-4 GHz). There are no amateur stations aboard the ISS for those bands yet, so the antennas support the Russian Glisser space helmet camera system. Having four antennas around the space station provides redundancy in case of failure and helps keep at least one antenna correctly oriented despite ISS attitude adjustments.
The ham radio presence is space came full circle in 2008 when Owen Garriott’s son Richard Garriott (W5KWQ) traveled as a paying passenger to the ISS with a Kenwood VC-H1 portable SSTV terminal and made hundreds of QSOs. Hams have been operating in space for over 30 years now, and there’s been a continuous ham station operating from orbit for better than a decade and a half. Amateur radio has provided inspiration and education to thousands of kids around the world and has been a source of crew comfort and well-being by providing communication with family and friends. As long as there are manned spacecraft, it’s a good guess that hams will be operating from them.
Amateur radio enthusiasts in the US will be interested in Faraday, an open-source digital radio that runs on 915 MHz, which amateur radio enthusiasts may know better as the 33 cm band.
You can transmit on 915 MHz without a license (in the US), taking advantage of the Industrial, Scientific, and Medical (ISM) exemption. This means that there’s commodity hardware available for sending and receiving, which is a plus. But you can’t do so with any real power unless you have an amateur radio license. And that’s what makes Faraday interesting — it makes it very easy to transmit and receive digital data, with decent power and range, if you’re licensed. The band is currently under-utilized, so go nuts!
The hardware design and documentation is online, and so is the firmware. The founders of the project would like you to build out a big network of these devices, possibly meshing them together. Our only regret is that the 33 cm band is only really open for use in the US, both with a license and without. Of course, there’s very little the Faraday team can do about that.
We’re no strangers to digital-mode amateur radio around here. But if you’re an amateur who hasn’t played around with digital modes yet, this might be a good way to get your feet wet.