radio

542 Articles

A Canned Ham Ham Antenna

November 16, 2023 by 29 Comments

If you’d have asked us for odds on whether you could successfully turn a canned ham into an amateur radio antenna, we’d have declined the offer. Now, having seen [Ben Eadie (VE6SFX)]’s “hamtenna” project, we’d look at just about any “Will it antenna?” project with a lot less skepticism than before.

To be painfully and somewhat unnecessarily clear about [Ben]’s antenna, the meat-like product itself is not in the BOM for this build, although he did use it as sustenance. Rather, it was the emptied and cleaned metal can that was the chief component of the build, along with a few 3D printed standoffs and the usual feedline and connectors. This is a slot antenna, a design [Ben] recently experimented with by applying copper foil tape to his car’s sunroof. This time around, the slot was formed by separating the top and bottom of the can using the standoffs and electrically connecting them with a strip of copper tape.

Connected to a stub of coax and a BNC connector, a quick scan with a NanoVNA showed a fantastic 1.26:1 SWR in the center of the 70-cm ham band, and a nearly flat response all the way across the band. Results may vary depending on the size of canned ham you sacrifice for this project; [Ben]’s can measured just about 35 cm around, a happy half-wavelength coincidence. And it actually worked in field tests — he was able to hit a local repeater and got good signal reports. All that and a sandwich? Not too shabby.

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Antennas Can Be A Total Mystery

October 10, 2023 by 14 Comments

The real action in the world of ham radio is generally in the high frequency bands. Despite the name, these are relatively low-frequency bands by modern standards and the antenna sizes can get a little extreme. After all, not everyone can put up an 80-meter dipole, but ham radio operators have come up with a number of interesting ways of getting on the air anyway. The only problem is that a lot of these antennas don’t seem as though they should work half as well as they do, and [MIKROWAVE1] takes a look back on some of the more exotic radiators.

He does note that for a new ham radio operator it’s best to keep it simple, beginning work with a dipole, but there are still a number of options to keep the size down. A few examples are given using helically-wound vertical antennas or antennas with tuned sections of coaxial cable. From there the more esoteric antennas are explored, such as underground antennas, complex loops and other ways of making a long wire fit in a small space, and even simpler designs like throwing a weight with a piece of wire attached out the window of an apartment building.

While antenna theory is certainly a good start for building antennas, a lot of the design of antennas strays into artistry and even folklore as various hams will have successes with certain types and others won’t. It’s not a one-size-fits-all situation so the important thing is to keep experimenting and try anything that comes to mind as long as it helps get on the air. A good starting point is [Dan Maloney]’s $50 Ham Guide series, and one piece specifically dealing with HF antennas.

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ESP32 Drives Tiny FM Radio

September 14, 2023 by 21 Comments

Even as music streaming services and podcast apps dominate most of our listening time, it’s still a great idea to keep a radio on hand, if for nothing else than in emergency situations. After all, blizzards, hurricanes, and other natural disasters can quickly take out both home and mobile Internet access. If you’d like to have an FM radio with the absolute smallest footprint, take a look at this one built around an ESP32.

While the radio uses the ESP32 as the main control board hosted by a TTGO T-Display board which adds a 1.14 inch ST7789V IPS panel, it also makes use of the TEA5767 chip for handling the FM radio signals. As [Volos Projects] has it programmed, the ESP32 stores five preset channels which can be toggled using two buttons at the bottom of the device. There’s also some circuitry to handle output to headphones or a stereo.

For making the radio even smaller, some of the audio processing could be done on the ESP32 instead, although its much simpler to take a slightly larger footprint and offload this to an audio processing chip. Since the source code for this project is open, modifications could be done including adding seek/tune functionality instead of relying only on presets. If you’re not building this for emergencies, though, and your entire area is dominated by cookie cutter corporate-owned radio stations, an ESP32 with an internet connection is great for accessing better radio stations around the world.

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Portrait Of A Long Wave Station In Its Twilight Years

September 13, 2023 by 25 Comments

There’s a quirk of broadcasting in Europe left over from the earliest days of the medium, which our American readers may not have encountered. As well as the familiar AM band, Europeans and Africans also have a so-called long wave band, on which you’ll find AM broadcast stations between about 150 and 280 kHz. Long wave transmissions were an ideal solution in the 1920s and 1930s to the problem of achieving national coverage from a single transmitter, and were widely used by state broadcasters. In an age of digital streaming they are increasingly irrelevant, and [Ringway Manchester] takes a look at one of Britain’s last long wave transmitter sites at Droitwich not too far from Birmingham.

The site covers around 50 acres, and is home to a variety of both medium wave (AM, for Americans), and a single long wave transmitter carrying BBC Radio 4 on 198 kHz. As he takes us through its history in the video below the break we hear a rundown of most of the major events in British broadcasting, while few Brits will have visited this unassuming field it’s likely most of us will have listened to something sent from here.

The long wave antenna is a T-shaped affair strung between two masts. We’re guessing that the radiator is the vertical portion, with the bar of the T forming a capacitance with the ground to make up for the radiator being a fraction of the 1515 meter wavelength. The video is something of a tribute to this once-vital station, as the Radio 4 transmissions are likely to stop in 2024 and the medium wave ones over the following years. We have to admit to catching our BBC transmissions online these days, but we still have to admit a pang of sadness at its impending end.

This reminds us, we’ve taken a fond look at AM radio in the past.

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It’s Numbers All The Way Down With This Tape Measure Number Station Antenna

September 6, 2023 by 12 Comments

For all their talk of cooperation and shared interests, the nations of the world put an awful lot of effort into spying on each other. All this espionage is an open secret, of course, but some of their activities are so mysterious that no one will confirm or deny that they’re doing it. We’re talking about numbers stations, the super secret shortwave radio stations that broadcast seemingly random strings of numbers for the purpose of… well, your guess is as good as ours.

If you want to try to figure out what’s going on for yourself, all you need is a pair of tape measures and a software defined radio (SDR), as [Tom Farnell] demonstrates. Tape measure antennas have a long and proud history in amateur radio and shortwave listening, being a long strip of conductive material rolled up in a convenient package. In this case, [Tom] wanted to receive some well-known numbers stations in the 20- to 30-meter band, and decided that a single 15-meter conductor would do the job. Unlike other tape measure antennas we’ve seen, [Tom] just harvested the blades from two 7.5-meter tape measures, connected them end-to-end, and threw the whole thing out the window in sort of a “sloper” configuration. The other end is connected to an RTL-SDR dongle and a smartphone running what appears to be SDRTouch, which lets him tune directly into the numbers stations.

Copying the transmissions is pretty simple, since they transmit either in voice or Morse; the latter can be automatically decoded on a laptop with suitable software. As for what the long strings of numbers mean, that’ll remain a mystery. If they mean anything at all; we like to think this whole thing is an elaborate plan to get other countries to waste time and resources intercepting truly random numbers that encode nothing meaningful. It would serve them right.

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USB-C Power For Ham Radio

September 5, 2023 by 28 Comments

Even though manufacturers of handheld ham radios have been busy adding all sorts of bells and whistles into their portable offerings, for some reason, many of them lack a modern USB-C port. In the same vein, while some have USB for programming or otherwise communicating between the radio and a computer, very few can use USB for power. Instead , they rely on barrel jacks or antiquated charging cradles. If you’d like to modernize your handheld radio’s power source, take a look at what [jephthai] did to his Yaesu.

In the past, USB ports could be simply soldered onto a wire and used to power basically anything that took 5 VDC. But the radio in question needs 12 volts, so the key was to find a USB-C cable with the built-in electronics to negotiate the right amount of power from USB-PD devices. For this one, [jephthai] cut the barrel connector off his radio’s power supply and spliced in some Anderson power pole connectors so he could use either the standard radio charger or one spliced onto this special cable.

With this fairly simple modification out of the way, it’s possible to power the handheld radio for long outings with the proper USB battery bank on hand. For plenty of situations this is much preferable to toting around a 12 V battery, which was the method of choice for powering things like QRP rigs when operating off-grid.

All-Mechanical Coil Winder Is A Scrap-Bin Delight

August 30, 2023 by 10 Comments

If there’s something more tedious than winding coils, we’re not sure what it is — possibly rolling and wrapping coins; that’s really a bother. But luckily, just like there are mechanical ways to count coins, there are tools to make coil production a little less of a chore, but perhaps none that have as much charm as this all-mechanical coil winder.

We’d say that [Ralph (VK3ZZC)]’s amazing invention firmly falls under the “contraption” category, without a hint of the term being used as a pejorative. The rig was based on the MoReCo Coilmaster, a machine that was once commercially available at a fairly steep price, according to [Ralph], and still seems to command a premium even today. Never being able to afford an original, [Ralph] spun up his own from scrap metal and tooling no more sophisticated than a drill press. It’s a riot of brass and steel, with a hand crank that drives the main winding shaft while powering a cam that guides the wire along the long axis of the coil form. Cams can be changed out for different winding patterns, and various chucks adapt to hold different coil forms to the winding shaft.

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