Author: Al Williams

4348 Articles

Modern Spark Gap Transmitter Uses A Rotary Gap

December 11, 2023 by 18 Comments

In the “don’t try this at home” category, [Joe Smith] builds a spark gap transmitter with a twist. The twist is that the drive power is from a signal generator attached to a FET. From there, though, things go classic using an automotive ignition coil and a tank circuit. He shows how adjusting the spark frequency changes the signal’s sound in a standard receiver.

We say don’t try this at home because the output of a transmitter like this will likely spew RF all over the place. Granted, there’s probably not much power, but it may well irritate your neighbors.

Switching to AM, you can really hear the tone from the spark frequency in the receiver. [Joe] posted some earlier videos where he made a 160-meter spark gap transmitter using an electric fly swatter. There are more details about how the tank circuits work in those videos. You can also see what the output looks like on a spectrum analyzer. You can hear what that transmitter sounds like, too.

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Fast Paper Tape For The Nuclear Family

December 10, 2023 by 8 Comments

We’ve enjoyed several videos from [Chornobyl Family] about the computers that controlled the ill-fated nuclear reactor in Chornobyl (or Chernobyl, as it was spelled at the time of the accident). This time (see the video below) they are looking at a high-speed data storage device. You don’t normally think of high-speed and paper tape as going together, but this paper tape reader runs an astonishing 1,500 data units per second. Ok, so that’s not especially fast by today’s standards, but an ASR33, for example, did about 10 characters per second.

An IBM2400 tape drive, for reference, could transfer at least 10 times that amount of data in a second, and a 3400 could do even better. But this is paper tape. Magnetic tape had much higher density and used special tricks to get higher speeds mechanically using vacuum columns. It was still a pretty good trick to move 4 meters of paper tape a second through the machine.

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SteamPunk Factory Comes To Life With An Arduino

December 10, 2023 by 15 Comments

It is one thing to make an artistic steampunk display. But [CapeGeek] added an Arduino to make the display come alive. The display has plenty of tubes and wires. The pressure gauge dominates the display, but there are lots of other interesting bits. Check it out in the video below.

From the creator:

The back-story is a fictional factory that cycles through a multistage process. It starts up with lights and sounds starting in a small tube in one corner, the needle on a big gauge starts rising, then a larger tube at the top lights up in different colors. Finally, the tall, glass reactor vessel lights up to start cooking some process. All this time, as the sequence progresses, it is accompanied by factory motor sounds and bubbling processes. Finally, a loud glass break noise hints that the process has come to a catastrophic end! Then the sequence starts reversing, with lights sequentially shutting down, the needle jumps around randomly, then decreases, finally, all lights are off, indicating the factory shutting down.

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Printing With Glass Fiber Filament

December 10, 2023 by 12 Comments

[ModBot] has been trying different engineering plastics for 3D printing. He recently looked at carbon fiber mixed with PET, but this time, he shows us his results with PET with glass fiber, or PET-GF. You can see how it all turned out in the video below.

The first part of the video compares the specifications, and, as you might expect, some factors are better for carbon fiber, and others are better for glass fibers. Once he gets to the printing, he covers the high temperatures needed (280-320C). He also talks about how either fiber will chew up nozzles and extruders.

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Clockhands For Faster CPU Execution

December 9, 2023 by 15 Comments

When you design your first homebrew CPU, you probably are happy if it works and you don’t worry as much about performance. But, eventually, you’ll start trying to think about how to make things run faster. For a single CPU, the standard strategy is to execute multiple instructions at the same time. This is feasible because you can do different parts of the instructions at the same time. But like most solutions, this one comes with a new set of problems. Japanese researchers are proposing a novel way to work around some of those problems in a recent paper about a technique they call Clockhands.

Suppose you have a set of instructions like this:

LOAD A, 10
LOAD B, 20
SUB A,B
LOAD B, 30
JMPZ  DONE
INC B

If you do these one at a time, you have no problem. But if you try to execute them all together, there are a variety of problems. First, the subtract has to wait for A and B to have the proper values in them. Also, the INC B may or may not execute, and unless we know the values of A and B ahead of time (which, of course, we do here), we can’t tell until run time. But the biggest problem is the subtract has to use B before B contains 30, and the increment has to use it afterward. If everything is running together, it can be hard to keep straight.

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Nanobots Self Replicate

December 9, 2023 by 11 Comments

Hey, what if you could have a factory that makes robots that is run by… robots? This is hardly an original thought, but we are a long way from having an assembly line of C3POs self-replicating. On the other hand, animals — including humans — self-replicate all the time using DNA. Now, scientists are making tiny nanorobots from DNA that can assemble more DNA, including copies of themselves.

Assembling 3D structures with DNA has deep implications. For example, it might be possible to build drugs in situ, delivering powerful toxins only to cancer cells. Another example would be putting DNA factories in diabetes patients to manufacture the insulin they can’t.

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Marconi Circuit Magnification Meter Gives Up Secrets

December 9, 2023 by 5 Comments

[Thomas] picked up a Marconi TF1245 with dents and dings. We have to admit that we had not heard of a “circuit magnification meter,” but apparently, this was a thing in the late 1960s and early 1970s. Turns out, we have heard of this kind of meter before, but it was called a Q meter. The device works using a very low-impedance resonant circuit and a very high-impedance voltmeter. It measures the ratio of the voltage across the known circuit and the unknown circuit. This particular meter needs an external signal source with very special characteristics. You can see the well-built device in the video below.

The unit didn’t seem to work, but we suspect that it didn’t like his normal signal source. According to a comment in the manual, the matching signal generator delivered 0.5V into a 0.5 ohm load. You could also use a matching transformer to get to the required match.

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