Is That Antenna Allowed? The Real Deal On The FCCs OTARD Rule

August 30, 2024 by Dan Maloney 111 Comments

The Hackaday comments section is generally a lively place. At its best, it’s an endless wellspring of the combined engineering wisdom of millions of readers which serves to advance the state of the art in hardware hacking for all. At its worst — well, let’s just say that at least it’s not the YouTube comments section.

Unfortunately, there’s also a space between the best and the worst where things can be a bit confusing. A case in point is [Bryan Cockfield]’s recent article on a stealth antenna designed to skirt restrictions placed upon an amateur radio operator by the homeowners’ association (HOA) governing his neighborhood.

Putting aside the general griping about the legal and moral hazards of living under an HOA, as well as the weirdly irrelevant side-quest into the relative combustibility of EVs and ICE cars, there appeared to be a persistent misapprehension about the reality of the US Federal Communications Commission’s “Over-the-Air Reception Devices” rules. Reader [Gamma Raymond] beseeched us to clarify the rules, lest misinformation lead any of our readers into the unforgiving clutches of the “golf cart people” who seem to run many HOAs.

According to the FCC’s own OTARD explainer, the rules of 47 CFR § 1.400 are intended only to prevent “governmental and nongovernmental restrictions on viewers’ ability to receive video programming signals” (emphasis added) from three distinct classes of service: direct satellite broadcasters, broadband radio service providers, and television broadcast services.

Specifically, OTARD prevents restrictions on the installation, maintenance, or use of antennas for these services within limits, such as dish antennas having to be less than a meter in diameter (except in Alaska, where dishes can be any size, because it’s Alaska) and restrictions on where antennas can be placed, for example common areas (such as condominium roofs) versus patios and balconies which are designated as for the exclusive use of a tenant or owner. But importantly, that’s it. There are no carve-outs, either explicit or implied, for any other kind of antennas — amateur radio, scanners, CB, WiFi, Meshtastic, whatever. If it’s not about getting TV into your house in some way, shape, or form, it’s not covered by OTARD.

It goes without saying that we are not lawyers, and this is not to be construed as legal advice. If you want to put a 40′ tower with a giant beam antenna on your condo balcony and take on your HOA by stretching the rules and claiming that slow-scan TV is a “video service,” you’re on your own. But a plain reading of OTARD makes it clear to us what is and is not allowed, and we’re sorry to say there’s no quarter for radio hobbyists in the rules. This just means you’re going to need to be clever about your antennas. Or, you know — move.

Coax Stub Filters Demystified

July 21, 2024 by Dan Maloney 9 Comments

Unless you hold a First Degree RF Wizard rating, chances are good that coax stubs seem a bit baffling to you. They look for all the world like short circuits or open circuits, and yet work their magic and act to match feedline impedances or even as bandpass filters. Pretty interesting behavior from a little piece of coaxial cable.

If you’ve ever wondered how stub filters do their thing, [Fesz] has you covered. His latest video concentrates on practical filters made from quarter-wavelength and half-wavelength stubs. Starting with LTspice simulations, he walks through the different behaviors of open-circuit and short-circuit stubs, as well as what happens when multiple stubs are added to the same feedline. He also covers a nifty online calculator that makes it easy to come up with stub lengths based on things like the velocity factor and characteristic impedance of the coax.

It’s never just about simulations with [Fesz], though, so he presents a real-world stub filter for FM broadcast signals on the 2-meter amateur radio band. The final design required multiple stubs to get 30 dB of attenuation from 88 MHz to 108 MHz, and the filter seemed fairly sensitive to the physical position of the stubs relative to each other. Also, the filter needed a little LC matching circuit to move the passband frequency to the center of the 2-meter band. All the details are in the video below.

It’s pretty cool to see what can be accomplished with just a couple of offcuts of coax. Plus, getting some of the theory behind those funny little features on PCBs that handle microwave frequencies is a nice bonus. This microwave frequency doubler is a nice example of what stubs can do.

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Are Hackers The Future Of Amateur Radio?

July 18, 2024 by Jenny List 120 Comments

If amateur radio has a problem, it’s that shaking off an image of being the exclusive preserve of old men with shiny radios talking about old times remains a challenge. Especially, considering that so many amateurs are old men who like to talk a lot about old times. It’s difficult to attract new radio amateurs in the age of the Internet, so some in the hobby are trying new avenues. [Dan, KB6NU] went to the recent HOPE conference to evangelise amateur radio, and came away having had some success. We agree with him, hackers can be the future of amateur radio.

He’s put up the slides from his talk, and in them he goes through all the crossovers between the two communities from Arduinos to GNU Radio. We don’t need persuading, in fact we’d have added UHF and microwave RF circuitry and pushing the limits of the atmosphere with digital modes such as WSPR to the list as our personal favourites. It seems he found willing converts, and it’s certainly a theme we’ve featured before here at Hackaday. After all, unless it retains its interest, amateur radio could just die away.

Tiny Transceiver Gets It Done With One Transistor

July 12, 2024 by Dan Maloney 23 Comments

When we first spotted the article about a one-transistor amateur radio transceiver, we were sure it was a misprint. We’ve seen a lot of simple low-power receivers using a single transistor, and a fair number of one-transistor transmitters. But both in one package with only a single active component? Curiosity piqued.

It turns out that [Ciprian Popica (YO6DXE)]’s design is exactly what it says on the label, and it’s pretty cool to boot. The design is an improvement on a one-transistor transceiver called “El Pititico” and is very petite indeed. The BOM has only about fifteen parts including a 2N2222 used as a crystal-controlled oscillator for both the transmitter and the direct-conversion receiver, along with a handful of passives and a coupe of hand-wound toroidal inductors. There’s no on-board audio section, so you’ll have to provide an external amplifier to hear the signals; some might say this is cheating a bit from the “one transistor” thing, but we’ll allow it. Oh, and there’s a catch — you have to learn Morse code, since this is a CW-only transmitter.

As for construction, [Ciprian] provides a nice PCB layout, but the video below seems to show a more traditional “ugly style” build, which we always appreciate. The board lives in a wooden box small enough to get lost in a pocket. The transceiver draws about 1.5 mA while receiving and puts out a fairly powerful 500 mW signal, which is fairly high in the QRP world. [Ciprian] reports having milked a full watt out of it with some modifications, but that kind of pushes the transistor into Magic Smoke territory. The signal is a bit chirpy, too, but not too bad.

We love minimalist builds like these; they always have us sizing up our junk bin and wishing we were better stocked on crystals and toroids. It might be good to actually buckle down and learn Morse too.

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Going Ham Mobile On A Bicycle

July 8, 2024 by Dan Maloney 19 Comments

It’s said that “Golf is a good walk spoiled,” so is attaching an amateur radio to a bike a formula for spoiling a nice ride?

Not according to [Wesley Pidhaychuk (VA5MUD)], a Canadian ham who tricked out his bike with a transceiver and all the accessories needed to work the HF bands while peddling along. The radio is a Yaesu FT-891, a workhorse mobile rig covering everything from the 160-meter band to 6 meters. [Wes] used some specialized brackets to mount the radio’s remote control head to the handlebars, along with an iPad for logging and a phone holder for streaming. The radio plus a LiFePO₄ battery live in a bag on the parcel rack in back. The antenna is a Ham Stick mounted to a mirror bracket attached to the parcel rack; we’d have thought the relatively small bike frame would make a poor counterpoise for the antenna, but it seems to work fine — well enough for [Wes] to work some pretty long contacts while pedaling around Saskatoon, including hams in California and Iowa.

The prize contact, though, was with [WA7FLY], another mobile operator whose ride is even more unique: a 737 flying over Yuma, Arizona. We always knew commercial jets have HF rigs, but it never occurred to us that a pilot who’s also a ham might while away the autopilot hours working the bands from 30,000 feet. It makes sense, though; after all, if truckers do it, why not pilots?

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Meccano-based Hellschreiber Machine

July 2, 2024 by Alexander Rowsell 10 Comments

[ZXGuesser] has pulled off a true feat of Meccano engineering: building a Meccano Hellschreiber machine. The design is a close replica of the original Siemens Feld-Hell machine as documented here. What is Hellschreiber, you might ask? It’s a very neat method of sending written messages over the air by synchronizing a printing wheel on the receiving end with pulses generated on the transmitter. By quickly moving the print wheel up and down, arbitrary figures can be printed out. If you want to learn more about Hellschreiber, check out this excellent Hackaday post from almost a decade ago!

The Mastodon thread linked above goes into more detail about the difficulty in building this behemoth — and the slight regret of sticking with the authentic QWERTZ keyboard layout! In order to use the Hellschreiber mode, you have to keep up a steady rhythm of typing at about 2.5 characters per second, otherwise, the receiving end will see randomly spaced gaps between each letter. So while having to type at a steady speed [ZXGuesser] also had to work with a slightly different keyboard layout. Despite this difficulty, some very good quality output was generated!

Incredibly, the output looks just like the output from the original, century-old design. We think this is an absolutely incredible accomplishment, and we hope [ZXGuesser] doesn’t follow through on disassembling this amazing replica — or if they do, we hope it’s documented well enough for others to try their hand at it!

Thanks [BB] for the tip!

UV-K5 All-Band Mod, Part 2: Easier Install, Better Audio, And Two Antennas

June 20, 2024 by Dan Maloney 46 Comments

OK, it’s official: the Quansheng UV-K5 is the king of hackable ham radios — especially now that a second version of the all-band hardware and firmware mod has been released, not to mention a new version of the radio.

If you need to get up to speed, check out our previous coverage of the all-band hack for the UV-K5, in which [Paul (OM0ET)] installs a tiny PCB to upgrade the radio’s receiver chip to an Si4732. Along with a few jumpers and some component replacements on the main board, these hardware mods made it possible for the transceiver, normally restricted to the VHF and UHF amateur radio bands, to receive everything down to the 20-meter band, in both AM and single-sideband modulations.

The new mod featured in the video below does all that and more, all while making the installation process slightly easier. The new PCB is on a flexible substrate and is considerably slimmer, and also sports an audio amplifier chip, to make up for the low audio output on SSB signals of the first version. Installation, which occupies the first third of the video below, is as simple as removing one SMD chip from the radio’s main board and tacking the PCB down in its footprint, followed by making a couple of connections with very fine enameled wire.

You could load the new firmware and call it a day at that point, but [Paul] decided to take things a step further and install a separate jack for a dedicated HF antenna. This means sacrificing the white LED on the top panel, which isn’t much of a sacrifice for most hams, to make room for the jack. Most of us would put a small SMA jack in, but [Paul] went for a BNC, which required some deft Dremel and knife work to fit in. He also used plain hookup wire to connect the jack, which sounds like a terrible idea; we’d probably use RG-316, but his mod didn’t sound that bad at all.

Keen to know more about the Quansheng UV-K5? Dive into the reverse-engineered schematics.

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