ham radio

241 Articles

1950’s AM Transmitter Is Fun But Dangerous

July 29, 2018 by 39 Comments

[Mr. Carlson] bought a Globe Scout Model 40A ham radio transmitter at a hamfest. The 40A was a grand old transmitter full of tubes, high voltage, and a giant transformer. It is really interesting to see how much things have changed over the years. The transmitter is huge but has comparatively few parts. You needed a crystal for the frequency you wanted to talk. There were two little modules that were precursors to hybrid circuits (which were precursors to ICs) that were often called PECs or couplates (not couplets) but other than those, it is all tubes and discrete components beautifully wired point-to-point.

The really surprising part, though, is the back panel. There’s a screw terminal to drive the coil of an external coaxial relay that has line voltage on it. There’s also a plug on the back with exposed terminals that has plate voltage on it which is considerable. In the 1950s, you assumed people operating equipment like this would be careful not to touch exposed high voltage.

Continue reading “1950’s AM Transmitter Is Fun But Dangerous” →

The Return Of RadioShack?

July 23, 2018 by 119 Comments

We’ve been following the ups and downs of Radio Shack for a while now, and it looks like another chapter is about to be penned in the storied retailer’s biography – and not Chapter 11 bankruptcy this time.

According to the ARRL website and major media reports, up to 50 of the 147 US locations of HobbyTown, the brick-and-mortar retailer of RC and other hobby supplies, will soon host a “RadioShack Express” outlet. Each outlet will be up to 500 square feet of retail space devoted to electronic components that would be of use to HobbyTown’s core customer base, as well as other merchandise and services.

HobbyTown locations in Mooresville, North Carolina, and Ontario, Ohio, will be among the first stores to get the RadioShack Express treatment. Current employees of the franchisees will staff the store-within-a-store, which will be stocked with RadioShack merchandise purchased by the store. Stores with Express outlets will have special RadioShack branding inside and out to attract customers. There’s talk of the deal being extended chain-wide if the pilot program goes well.

Back from the Ashes?

This is obviously great news for the beleaguered electronics retailer that was once a neighborhood fixture. True, its parts selection was often less than complete, more so in recent years than in the chain’s heyday in the mid-1970s and early 1980s. And it’s true that prices were often astronomical compared to buying online. But on a Sunday afternoon, The Shack was a lifesaver for that last minute part needed to finish a project, and the premium was well worth the convenience. Watching the decline of the chain and seeing stores disappear one by one was a slow, sad process, so that makes this seems like an unqualified positive development.

But is it? On the face of it, there’s a lot of synergy between the HobbyTown offerings and what could be stocked in a RadioShack Express. I’ve never actually visited a HobbyTown myself — I plan to fix that now that I know I’ve got an outlet nearby, even if it doesn’t appear to be on the list of 50 early Express locations — so I can only go by what I see listed online for merchandise. But a store that sells every conceivable part for RC cars and planes, drones, model rockets, and STEM-related toys and kits seems a likely place to find customers for RadioShack’s offerings.

It won’t be clear until someone sees one of these Express kiosks first hand and reports back, but it seems like we might see something like the old “cabinet o’ components” that was found in the back of the most recent incarnation of RadioShack retail stores, along with a few shelves full of things like solder, wire, and tools. There may also be some items in the Arduino-Pi space, which would be really exciting, although that might run afoul of existing HobbyTown offerings. Still, one-stop shopping of everything from servos to MOSFETs would be a huge win for electronics hobbyists.

Not the Cell Phones Again!

But there may be cause for concern. Reports are that RadioShack Express locations will also offer services such as cell phone repairs. Dipping a toe into the cell phone market seemed to be the beginning of the end for RadioShack the first time through, and by the time it was clear to everyone that the chain was on death’s door, it was hard to go into a RadioShack store without being bombarded by cell phone sales pitches. To be brutally frank, I don’t take the early inclusion of cell phone repairs as an encouraging sign of the long-term viability of the RadioShack Express concept. Do we really need another place that fixes cell phones? The areas that HobbyTown stores tend to locate are rife with places that fix phones already, so I just don’t see the point. And it just smacks of the bad old days of RadioShack.

Still, I’m cautiously optimistic that this is a positive development for RadioShack, and I think it’s a win for electronics hobbyists overall. I’ll be keeping my eye on my local HobbyTown for the return of that iconic RadioShack logo, and looking forward to the day that I can pay a buck for a resistor again. Until then, if any readers happen to be near one of the combined locations when they open next week, we’d love a boots-on-the-ground report. Post your observations in the comments below, and pix or it didn’t happen.

[via r/amateurradio]

Portable Ham Radio Design Fosters Experiments

June 16, 2018 by 4 Comments

[Charlie Morris] has been busy building a portable ham radio rig and documenting his progress in a series of videos. You can see the first one below. There’s four parts (more if you count things like part 4 and part 4a as two parts) so far and it is always interesting to see inside a build like this, where the choices and tradeoffs are explained.

The first part covers the Si5351 VFO and the associated display. There’s very little to the VFO other than off-the-shelf modules including an Arduino. You can also see the portable Morse code key which is actually a micro switch. The second part experiments with audio amplifiers. [Charlie] looked at the NE5534 vs discrete amplifiers. He was shooting for lowest current draw that was usable. Other parts discuss the RF amplifier and the receiver. Despite the VFO, there is quite a bit of non-module parts by the time things start shaping up.

Continue reading “Portable Ham Radio Design Fosters Experiments” →

Homebrew SDR Ham Radio In 9 Parts

June 6, 2018 by 31 Comments

It used to be homebrew ham gear meant something simple. A couple of active devices that could send CW. Maybe a receiver with a VFO. But only the most advanced builders could tackle a wide range SSB transceiver. Today, that goal is still not trivial, but it is way easier due to specialty ICs, ready access to high-speed digital signal processing, and advances in software-defined radio techniques. [Charlie Morris] decided to build an SSB rig that incorporated these technologies and he shared the whole process from design to operation in a series of nine videos. You can see the first one below.

The NE612 is a child of the popular NE602 chip, which contains a Gilbert-cell mixer, and an oscillator that makes building a receiver much easier than it has been in the past. The chips are set up as direct conversion receivers and feed a Teensy which does the digital signal processing on the recovered audio.

Continue reading “Homebrew SDR Ham Radio In 9 Parts” →

Ham Radio On $100 Or Less

May 28, 2018 by 63 Comments

There are a lot of reasons to get a ham radio license, and if you are one of those that think ham radio is dead you can probably skip this post. However, if you have been interested, but didn’t want to drop a lot of money on a station, [KE6MT] has got some great advice for you. He says you can have a rewarding time in ham radio for about $100 of spending.

The post is the advice he wished he had been given in 2015 when he got his license. It turns out you can get on the air very inexpensively these days, especially if you aren’t afraid to build gear from kits.

Continue reading “Ham Radio On $100 Or Less” →

Raspberry Pi Is Up Up And Away

May 2, 2018 by 3 Comments

BACAR — Balloon Carrying Amateur Radio — is just what it sounds like. A high-altitude balloon carries experiments and communicates via amateur radio. [ZR6AIC] decided to fly a payload in a local BACAR experiment. The module would send its GPS position via the APRS network and also send a Morse code beacon every seven minutes. It also sends other data such as temperature, and has an optional camera fitted.

The hardware used was the ubiquitous Raspberry Pi along with an associated daughterboard for transmitting on the 2 meter ham band. An RTL dongle took care of the receive portion and another dongle provided GPS. A DS18B20 temperature sensor provides the temperature data.

Continue reading “Raspberry Pi Is Up Up And Away” →

Drink Lots Of Beer To Raise Your Monopole

January 26, 2018 by 19 Comments

When we published a piece about an ADS-B antenna using a Coke can as a groundplane, Hackaday reader [2ftg] got in contact with us about something with a bit more… stature.

A monopole groundplane antenna is a single vertical conductor mounted on an insulator and rising up above a conductive groundplane. In radio terms the groundplane is supposed to look as something of a mirror, to provide a reflection of what would come from the other half of a dipole were there to be two conductors. You can use anything conductive as your monopole, a piece of wire, (in radio amateur humour) a piece of wet string, or even beer cans. “Beer cans?” you ask incredulously, expecting this to be another joke. Yes, beer cans, and [2ftg] has been good enough to supply us with a few examples. The first is a 57-foot stack of them welded together in the 1950s for use on the 80 metre band ( we suspect steel cans may have been more common than aluminum back then), the second is a more modest erection for the 2 metre band, and the final one consists of photographs only of an HF version that looks a little wavy and whose cans are a little less beery.

The reporting in the 1950s piece is rather cheesy, but does give a reasonable description of it requiring welding rods as reinforcement. It also gives evidence of the antenna’s effectiveness, showing that it could work the world. Hardly surprising, given that a decent monopole is a decent monopole no matter how many pints of ale you have dispatched in its making.

The Coke can ADSB can be seen in all its glory here, and if all this amateur radio business sounds interesting, here’s an introduction.

Beer cans picture: Visitor7 [CC BY-SA 3.0].