Loading Coils, The Heaviside Condition, And Pupin Coils

June 19, 2020 by Al Williams 27 Comments

When we draw schematics, we have the luxury of pretending that wire is free. There are only a few cases where you have to account for the electrical characteristics of wire: when the wire is very long or the frequency on the wire is relatively high.

This became apparent after the first transatlantic cable went into service for telegraph communications. Even though the wire was linear, there was still distortion on the line so severe that dots and dashes would overlap each other. The temporary solution was to limit speeds so slow that operators had trouble sending and receiving at those speeds. How slow? An average character took two minutes to send! That’s not a typo. Two minutes per character. By custom, Morse code assumes a word is five characters, so you could send a word every 10 minutes.

The first transatlantic cable went into service in 1858 and was virtually the moon landing of its day. Frustrated with how slow the communications were, an electrician by the name of Whitehouse decided to crank up the voltage to over 1,000 volts which caused the cable to fail after only three weeks in service. Whoops. Later analysis showed the cable was probably going to fail quickly anyway, but Whitehouse took the public blame.

The wire back then wasn’t as good as what we have today, which led to some of the problems. The insulation was made from multiple coats of a natural latex, gutta percha, which is what dentists use to fill root canals. The jackets were made from tarred hemp and bound with iron wire. There was no way to build an underwater amplifier in 1858, so the cables were just tremendous wires laying on the ocean floor between Newfoundland and Ireland.

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Clear Some Space And Build A Cosmo Clock

May 10, 2020 by Kristina Panos 4 Comments

Like many of us, [Artistikk] is inspired by astronauts and space travel in general. To keep the inspiration coming, he made the Cosmo Clock — a sleek little clock that changes color whenever an astronaut is launched into space.

As awesome as space is, we’re inspired by the amount of Earth-saving reuse going on in this project. The actual time-telling is coming from a recycled wristwatch movement. [Artistikk] cut a bigger set of hands for it out of a plastic container, and used the lid from another container for the clock’s body.

The launch inquiries are handled by an ESP8266, which uses a Blynk app and some IFTTT magic to get notified whenever NASA yeets an astronaut into space. Then the ESP generates random RGB values and sends them to a single RGB LED. The clock body is small enough that a single LED is bright enough to light up all the parts that aren’t blacked out with thick paper. In case you’re wondering, the pattern around the edge isn’t random, it’s Morse code for ‘sky’, but you probably already knew that, right? Make a dash past the break to take the tour.

Clocks that wind up in space are much more complicated. Check out this tear-down of the clock from a late-90s Soyuz spacecraft.

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Typing By Slamming Your Laptop Closed. Repeatedly

April 4, 2020 by Danie Conradie 26 Comments

Do you sometimes feel that your custom mechanical keyboard is not quite loud enough to proclaim your superior hacking powers? Or do you need a more forceful way shout in all caps at someone who is wrong on the internet? For all this and more, [Jesse Li] has got you covered, with a set of bash scripts that allows you to type by slamming your laptop closed repeatedly, using Morse code.

Not the fastest way to type, but definitely the most forceful

The scripts are quite simple, and work receiving the lid open/close events from ACPI (Advanced Configuration and Power Interface), recording the open and close timestamp and converting the timing to dots and dashes. After slamming to the required rhythm, you keep the lid open to see the character appear.

Why would want this? Well, you can now type the letter E by closing your laptop, instead of locking it. Maybe use it to send an emergency message while you’re being held by terrorists in a B-grade action movie. Otherwise, we think this is just an entertaining little hack that’s probably the product of quarantine induced boredom.

Morse code, otherwise known as CW, is still in surprisingly widespread use by ham radio operators, because it’s good at getting messages across intercontinental distances when signal conditions are bad and CW-only ham radio gear is cheap and easy to build yourself. We’ve also covered the Koch Method of learning CW, so don’t be afraid to dabble a bit during the quarantine.

Learning Morse Code The Ludwig Koch Way

February 21, 2020 by Al Williams 54 Comments

Most countries have dropped the requirement for learning Morse code to become a ham radio operator. Because of that, you might think Morse code is dead. But it isn’t. Some people like the nostalgia. Some like that you can build simple equipment to send and receive Morse code. Others like that Morse code is much more reliable than voice and some older digital modes. Regardless of the reason, many people want to learn Morse code and it is still a part of the ham radio scene. The code has a reputation of being hard to learn, but it turns out that is mostly because people haven’t been taught code in smart ways.

I don’t know if they still do, but some youth organizations used to promote some particularly bad ways to learn the code. The second worse way is to learn “dots and dashes” and many people did learn that way. The very worst way was using an image like the adjacent one to try to map the dots and dashes into letter shapes. This chart dates back to at least 1918 when a Girl Guides handbook printed it.

Even if you are a visual learner, this is a bad idea. The problem is, it is nearly impossible to hear sounds at 20 or 30 words per minute and map them to this visual representation. Another visual method is to use a binary tree where left branches are dots and right branches are dashes.

If you only need to master 5 words per minute to get a merit badge, you might get away with this. But for real use, 5 words a minute is very slow. For example, this sentence would take about 3 minutes to send at that speed. Just that one sentence.

So what are the better ways? Let’s take a look.

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Raspberry Pi Ham Radio Remote Reviewed

October 7, 2019 by Al Williams 18 Comments

One problem with ham radio these days is that most hams live where you can’t put a big old antenna up due to city laws and homeowner covenants. If you’re just working local stations on VHF or UHF, that might not be a big problem. But for HF usage, using a low profile antenna is a big deal. However, most modern radios can operate remotely. Well-known ham radio company MFJ now has the RigPi Station Server and [Ham Radio DX] has an early version and did a review.

As the name implies, the box contains a Raspberry Pi. There’s also an audio interface. The idea is to consolidate rig control along with other station control (such as rotators) along with feeding audio back and forth to the radio. It also sends Morse code keying to the radio. The idea is that this box will put your radio on the network so that you operate it using a web browser on a PC or a mobile device.

According to MFJ, you can operate voice, Morse code, or digital modes easily and remotely. The box uses open source software that can control over 200 different radios and 30 rotors. Of course, you could build all this yourself and use the same open source software, but it is nicely packaged. [Ham Radio DX] says you don’t need to know much about the Pi or Linux to use the box, although clearly you can get into Linux and use the normal applications if you’re so inclined.

Even if you don’t want to transmit, we could see a set up like this being used for remote monitoring. We’d like to see a companion box for the remote end that had the audio hardware, a keyer, and perhaps a knob to act as a remote control of sorts. Of course, you could probably figure out how to do that yourself. We wonder if some ham clubs might start offering a remote radio via an interface like this — we’ve seen it done before, but not well.

Your $50 radio probably isn’t going to work with this, and if you use FT8, you could argue you don’t need to be there anyway.

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Learn Morse Code, Clockwork Orange Style

September 10, 2019 by Al Williams 11 Comments

You might have to provide your own wrist straps and eye clamps, but if you want to learn Morse code, [Seth] has a web site for you. You can get code practice using the Farnsworth method and each letter is flashed before you as it is sent, which we assume will burn it into your brain.

Why learn Morse code now? Just about all countries now have at least some no code ham licenses and many have taken code off the tests completely. However, there are still many hams that use the code even today. Why? The personal challenge is part of it and perhaps nostalgia. However, it is also true that Morse code transmitters and receivers are dead simple to build and can get through where other simple radios can’t.

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Blue Pill Makes Cheap But Powerful Morse Tutor

August 7, 2019 by Al Williams 2 Comments

[W8BH] attended a talk by another ham, [W8TEE] that showed a microcontroller sending and receiving Morse code. He decided to build his own, and documented his results in an 8 part tutorial. He’s using the Blue Pill board and the resulting device sends code with paddles, sends canned text, provides an LCD with a rotary knob menu interface, and even has an SD card for data storage.

All the code is on GitHub. If you are interested in Morse code or in learning how to write a pretty substantial application using the Blue Pill and the Arduino IDE (or any other similar processor), this is a great exposition that is also a practical tool.

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