Day: April 25, 2019

The $50 Ham: Dummy Loads

April 25, 2019 by 41 Comments

This is an exciting day for me — we finally get to build some ham radio gear! To me, building gear is the big attraction of amateur radio as a hobby. Sure, it’s cool to buy a radio, even a cheap one, and be able to hit a repeater that you think is unreachable. Or on the other end of the money spectrum, using a Yaesu or Kenwood HF rig with a linear amp and big beam antenna to work someone in Antartica must be pretty cool, too. But neither of those feats require much in the way of electronics knowledge or skill, and at the end of the day, that’s why I got into amateur radio in the first place — to learn more about electronics.

To get my homebrewer’s feet wet, I chose perhaps the simplest of ham radio projects: dummy loads. Every ham eventually needs a dummy load, which is basically a circuit that looks like an antenna to a transmitter but dissipates the energy as heat instead of radiating it an appreciable distance. They allow operators to test gear and make adjustments while staying legal on emission. Al Williams covered the basics of dummy loads a few years back in case you need a little more background.

We’ll be building two dummy loads: a lower-power one specifically for my handy talkies (HTs) will be the subject of this article, while a bigger, oil-filled “cantenna” load for use with higher power transmitters will follow. Neither of my designs is original, of course; borrowing circuits from other hams is expected, after all. But I did put my own twist on each, and you should do the same thing. These builds are covered in depth on my Hackaday.io page, but join me below for the gist on a good one: the L’il Dummy.

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The Galaxy Fold, Or Why Flexible OLED May Not Yet Be Ready For Prime Time

April 25, 2019 by 92 Comments

Samsung’s fancy new high-end smartphone with a flexible, foldable OLED display has been failing in worrying numbers for the first reviewers who got their hands on one. Now iFixit has looked into the issue using their considerable amount of smartphone tear-down experience to give their two cents. They base many of their opinions on the photos and findings by the Verge review, who were one of the (un)lucky ones to have their unit die on them.

The Galaxy Fold was supposed to be this regular smartphone sized phone which one can open up fully to reveal a tablet-sized display inside. The use of a flexible OLED display was supposed to create a seamless display without the annoying center line that having two individual displays would produce. Unfortunately it’s this folding feature which produces issues.

As iFixit notes, OLEDs are rather fragile, with their own tear-downs of regular OLED-equipped devices already often resulting in the damaging of the display edges, which spells doom for the internals of them as oxygen and other contaminants can freely enter. This means that maintaining this barrier is essential to keep the display functioning.

This is probably the reason why Samsung chose to install a screen protector on the display, which unfortunately was mistaken for a protective foil as found on many devices. The subsequent removal of this protector by some reviewers and the mechanical stress this caused destroyed some screens. Others had debris trapped in the fold between both halves of the display, which caused visible bumps in the display when opened.

The relatively massive spacing between the hinge and the display seems almost purposefully engineered to allow for the ingress of debris. This combines with the lack of any guiding crease in the center of the display and the semi-random way in which humans open and close the Fold compared to the perfectly repeating motion of the folding robots Samsung used to test the display. It seems that Samsung and others still have some work to do before they can call folding OLED displays ready for production.

Finally, have a look at this video of Lewis from UnboxTherapy pulling a folding robot with opening and closing a Fold one-thousand times:

 

This GPS Speedometer Hangs Off Your Handlebars

April 25, 2019 by 9 Comments

If you can ride a bike with no handlebars, no handlebars, no handlebars, you can do just about anything. You can take apart a remote control, and you can almost put it back together. You can listen in on a two meter repeater and you can build a GPS module speedometer. That’s what [Jeremy Cook] did with just a few parts, a little 3D design, and some handy zip ties to hold it onto the handlebars, the handlebars.

The electronics for this build are relatively simple, based on an Arduino Pro Mini because that’s just about the smallest readily available development board you’ll be able to find. To this is a LiPo, a LiPo charging circuit, a GPS module, and a single RGB LED. The code gets some data from the GPS module and figures out a speed. This is then translated into a color — red, yellow, or green depending on whether you’re stationary, below 5 km/h, or above 5 km/h.

All these electronics are stuffed into a 3D-printed enclosure. The majority of the enclosure is printed in black, with a translucent top that serves as a great diffuser for the LED. Just two zip ties hold this GPS speedometer onto the handlebars, and from the video below, everything looks great. The GPS module does take some time to get data at first, but that’s a common problem with GPS units that have been powered off for a few days. If only someone made a GPS module that could keep time with no metronome, with no metronome.

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