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145 Articles

Tiny Transceiver Gets It Done With One Transistor

July 12, 2024 by 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.

Continue reading “Tiny Transceiver Gets It Done With One Transistor” →

Going Ham Mobile On A Bicycle

July 8, 2024 by 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?

Continue reading “Going Ham Mobile On A Bicycle” →

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

June 20, 2024 by 48 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.

Continue reading “UV-K5 All-Band Mod, Part 2: Easier Install, Better Audio, And Two Antennas” →

A Super-Simple Standalone WSPR Beacon

June 14, 2024 by 26 Comments

We’ve said it before and we’ll say it again: being able to build your own radios is the best thing about being an amateur radio operator. Especially low-power transmitters; there’s just something about having the know-how to put something on the air that’ll reach across the planet on a power budget measured in milliwatts.

This standalone WSPR beacon is a perfect example. If you haven’t been following along, WSPR stands for “weak-signal propagation reporter,” and it’s a digital mode geared for exploring propagation that uses special DSP algorithms to decode signals that are far, far down into the weeds; signal-to-noise ratios of -28 dBm are possible with WSPR.

Because of the digital nature of WSPR encoding and the low-power nature of the mode, [IgrikXD] chose to build a standalone WSPR beacon around an ATMega328. The indispensable Si5351 programmable clock generator forms the RF oscillator, the output of which is amplified by a single JFET transistor. Because timing is everything in the WSPR protocol, the beacon also sports a GPS receiver, ensuring that signals are sent only and exactly on the even-numbered minutes. This is a nice touch and one that our similar but simpler WSPR beacon lacked.

This beacon had us beat on performance, too. [IgrikXD] managed to hit Texas and Colorado from the edge of the North Sea on several bands, which isn’t too shabby at all with a fraction of a watt.

Thanks to [STR-Alorman] for the tip.

[via r/amateurradio]

Passive Diplexer Makes One Antenna Act Like Two

May 22, 2024 by 24 Comments

Stay in the amateur radio hobby long enough and you might end up with quite a collection of antennas. With privileges that almost extend from DC to daylight, one antenna will rarely do everything, and pretty soon your roof starts to get hard to see through the forest of antennas. It may be hell on curb appeal, but what’s a ham to do?

One answer could be making one antenna do the work of two, as [Guido] did with this diplexer for dual APRS setups. Automatic Packet Reporting System is a packet radio system used by hams to transmit telemetry and other low-bandwidth digital data. It’s most closely associated with the 2-meter ham band, but [Guido] has both 2-meter (144.8-MHz) and 70-cm LoRa (433.775-MHz) APRS IGates, or Internet gateway receivers. His goal was to use a single broadband discone antenna for both APRS receivers, and this would require sorting the proper signals from the antenna to the proper receiver with a diplexer.

Note that [Guido] refers to his design as a “duplexer,” which is a device to isolate and protect a receiver from a transmitter when they share the same antenna — very similar to a diplexer but different. His diplexer is basically a pair of filters in parallel — a high-pass filter tuned to just below the 70-cm band, and a low-pass filter tuned just above the top of the 2-m band. The filters were designed using a handy online tool and simulated in LTSpice, and then constructed in classic “ugly” style. The diplexer is all-passive and uses air-core inductors, all hand-wound and tweaked by adjusting the spacing of the turns.

[Guido]’s diplexer performs quite well — only a fraction of a dB of insertion loss, but 45 to 50 dB attenuation of unwanted frequencies — pretty impressive for a box full of caps and coils. We love these quick and dirty tactical builds, and it’s always a treat to see RF wizardry in action.

Matchbox Transceiver Pushes The Spy Radio Concept To Its Limits

May 9, 2024 by 23 Comments

The Altoids tin has long been the enclosure of choice for those seeking to show off their miniaturization chops. This is especially true for amateur radio homebrewers — you really have to know what you’re doing to stuff a complete radio in a tiny tin. But when you can build an entire 80-meter transceiver in a matchbox, that’s a whole other level of DIY prowess.

It’s no surprise that this one comes to us from [Helge Fykse (LA6NCA)], who has used the aforementioned Altoids tin to build an impressive range of “spy radios” in both vacuum tube and solid-state versions. He wisely chose solid-state for the matchbox version of the transceiver, using just three transistors and a dual op-amp in a DIP-8 package. There’s also an RF mixer in an SMD package; [Helge] doesn’t specify the parts, but it looks like it might be from Mini-Circuits. Everything is mounted dead bug style on tiny pieces of copper-clad board that get soldered to a board just the right size to fit in a matchbox.

A 9 volt battery, riding in a separate matchbox, powers the rig. As do the earbud and tiny Morse key. That doesn’t detract from the build at all, and neither does the fact that the half-wave dipole antenna is disguised as a roll of fishing line. [Helge]’s demo of the radio is impressive too. The antenna is set up very low to the ground to take advantage of near vertical incidence skywave (NVIS) propagation, which tends to direct signals straight up into the ionosphere and scatter them almost directly back down. This allows for medium-range contacts like [Helge]’s 239 km contact in the video below.

Banging out Morse with no sidetone was a challenge, but it’s a small price to pay for such a cool build. We’re not sure how much smaller [Helge] can go, but we’re eager to see him try.

Continue reading “Matchbox Transceiver Pushes The Spy Radio Concept To Its Limits” →

Open HT Surgery Gives Cheap Transceiver All-Band Capabilities

March 22, 2024 by 34 Comments

Watch out, Baofeng; there’s a new kid on the cheap handy talkie market, and judging by this hardware and firmware upgrade to the Quansheng UV-K5, the radio’s hackability is going to keep amateur radio operators busy for quite a while.

Like the ubiquitous Baofeng line of cheap transceivers, the Quansheng UV-K5 is designed to be a dual-band portable for hams to use on the 2-meter VHF and 70-centimeter UHF bands. While certainly a useful capability, these bands are usually quite range-limited, and generally require fixed repeaters to cover a decent geographic area. For long-range comms you want to be on the high-frequency (HF) bands, and you want modulations other than the FM-only offered by most of the cheap HT radios.

Luckily, there’s a fix for both problems, as [Paul (OM0ET)] outlines in the video below. It’s a two-step process that starts with installing a hardware kit to replace the radio’s stock receiver chip with the much more capable Si4732. The kit includes the chip mounted on a small PCB, a new RF choke, and a bunch of nearly invisible capacitors. The mods are straightforward but would certainly benefit from the help of a microscope, and perhaps a little hot air rework. Once the hardware is installed and the new firmware flashed, you have an HT that can receive signals down to the 20-meter band, with AM and SSB modulations, and a completely redesigned display with all kinds of goodies.

It’s important to note that this is a receive-only modification — you won’t be transmitting on the HF bands with this thing. However, it appears that the firmware allows you to switch back and forth between HF receive and VHF/UHF transceive, so the radio’s stock functionality is still there if you need it. But at $30 for the radio and $12 for the kit, who cares? Having a portable HF receiver could be pretty handy in some situations. This looks like yet another fun hack for this radio; we’ve seen a few recently, including a firmware-only band expansion and even a Trojan that adds a waterfall display and a game of Pong. Continue reading “Open HT Surgery Gives Cheap Transceiver All-Band Capabilities” →