Day: December 5, 2023

Directional Antenna Stands Tall

December 5, 2023 by 7 Comments

When you think of directional ham radio antennas, you probably think of a Yagi, cubical quad, or a log-periodic antenna. These antennas usually are in a horizontal configuration up on a high tower. However, it is possible to build beams with a vertical orientation and, for some lower frequencies, it is far more practical than mounting the elements on a boom. [DXCommander] shows us his 40 meter two-element vertical antenna build in the video below.

A typical Yagi is just a dipole with some slightly longer or shorter elements to direct or reflect the signal. A normal vertical, however, is nothing more than half of a dipole that uses the ground as the other half. So it is possible to create reflectors and directors with a vertical-driven element.

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Inside A Rubidium Frequency Standard

December 5, 2023 by 14 Comments

We think of crystals as the gold standard of frequency generation. However, if you want real precision, you need something either better than a crystal or something that will correct for tiny errors — often called disciplining the oscillator. [W3AXL] picked up a rubidium reference oscillator on eBay at a low cost, and he shows us how it works in the video you can see below. He started with a GPS-disciplined oscillator he had built earlier and planned to convert it to discipline from the rubidium clock.

The connector looks like a D-shell connector superficially, but it has a coax connector in addition to the usual pins. The device did work on initial powerup, and using a lissajous pattern to compare the existing oscillator with the new device worked well.

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This Pogo Pin Test Fixture Keep Your SMDs From Taking Flight

December 5, 2023 by 12 Comments

There’s no denying how useful surface mount technology is, and how enabling the ability to make really small circuits has become. It comes at a price, though; most of us probably know what it’s like for the slightest wrong move to send a part the size of a grain of sand into another dimension.

To help make testing these parts a little easier, [IMSAI Guy] has come up with this clever little SMD test fixture. It’s designed to hook up to another custom board, which in turn connects to a wonderful old Hewlett-Packard 4275A LCR meter. The jig is based on two pogo pins mounted directly across from each other on a scrap of single-clad PCB. The spring-loaded contacts, which short together when not in use, are pulled apart to load an SMD part, like the 1-μH inductors shown in the video below. The pins hold the component firmly and make good electrical contact, allowing hands-free testing without the risk of an errant touch of the test probes sending it flying.

While the test fixture works well for larger SMDs, we could see this being a bit fussy for smaller parts. That would be easy enough to fix with perhaps some 3D-printed arms that retract the pogo pins symmetrically, holding them open until the part is loaded. A centering fixture might help too, as would a clear shield to contain any parts that get the urge to go for a ride. But, for the tactical application [IMSAI Guy] has in mind, this sure seems like enough.

Just getting into surface mount? If so, you might want to check out this handy guide to the often cryptic markings used on SMD parts.

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Affordable Networking For Your Classic Mac

December 5, 2023 by 1 Comment

The Mac SE and in particular the Mac SE/30 number among the more sought-after of the classic all-in-one Apple computers, and consequently their peripherals including network cards are also hard to find and pricey. Even attempts at re-creating them can be expensive, usually because the chips used back in the day are now nearly unobtainable. But if the search is widened to other silicon it becomes possible to create substitutes, as [Richard Halkyard] is doing with a modern version of the SE Ethernet card.

The chip which makes this possible is the Microchip ENC624J600, an embedded 10/100 Ethernet controller with an impressively configurable interface that can be easily mated to the 68k bus. For The SE it’s mapped to a memory area, while for the /30 there can be a declaration ROM which informs the machine where it is.

This is an as yet unfinished project, a work in progress. But it deserves to succeed, and if we can provide encouragement by featuring it here then it’s definitely worth a look. Or course, this is by no means the only replacement for an original board.

SE/30 picture: Cornellanense, CC BY-SA 4.0.

Retrotechtacular: The Gunsmith Of Williamsburg

December 5, 2023 by 11 Comments

A modern firearm is likely to be mass-produced using high-precision machine tools, and with a uniformity to the extent that parts from one can be interchanged with those from another. This marks a progression of centuries of innovation, in gunsmithing, in machine tooling, and in metallurgy. In the 18th century there was little of the innovations found in a modern weapon, and a rifle would have been made entirely by hand through the work of a master gunsmith. The video below the break is a fascinating 1969 film following Wallace Gusler, the gunsmith at the museum town of Williamsburg, Virginia, as he makes an 18th-century muzzle-loading flintlock rifle from raw materials. It’s a long video, but it leaves nothing out and has a really informative commentary we’re told from the gunsmith himself.

The film opens with a piece of wrought iron being forged into a long strip. We’ve talked about wrought iron as a difficult-to-find blacksmith’s material before here, so this immediately makes us curious as to what material the current Williamsburg gunsmiths use. The strip is formed round a mandrel and laboriously forge-welded to form a rough tube, before being bored with a series of drills and then rifled with a toothed slug. The finishing is done by had with a file, with the rough tube being filed to an octagonal shape. Continue reading “Retrotechtacular: The Gunsmith Of Williamsburg” →

A Single Board Computer, With Vacuum Tubes

December 5, 2023 by 8 Comments

We have occasionally featured vacuum tube computers here at Hackaday and we’ve brought you many single board computers, but until now it’s probable we haven’t brought you a machine that combined both of these things. Now thanks to [Usagi Electric] we can see just such a board, in the form of his UE-0.1, a roughly 260 by 210 mm PCB with 24 6AU6 pentodes on board that implements a simple one-bit CPU.

The architecture starts with the MC14500B 1-bit microcontroller, which was the subject of a previous vacuum tube computer. People found the unusual architecture difficult to understand, so this board is an even simpler take. It doesn’t have all the features of the Motorola original but it is (just) enough to be a CPU.

The tubes are arranged in groups of four with heaters in series from a 24 V supply, while the inputs and clock come in the form of on-board suitably retro-looking switches. The final touch is a VFD of the type used in bar graphs, were used to show the state of the various bits. It’s a fully working computer in the simplest sense, and definitely worth a look in the video below the break.

It would be interesting to see whether the tube count could be reduced further, or is this a record. The number of physical devices could be cut by using tubes with more than one device in them such as double-triodes, but perhaps that would be cheating.

Meanwhile, if you think vacuum computing is all about the old stuff, perhaps you should look at the state of the art.

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Mining And Refining: Titanium, Our Youngest Industrial Metal

December 5, 2023 by 9 Comments

Earlier in this series, we made the case for copper being “the metal that built technology.” Some readers took issue with that statement, noting correctly that meteoric iron and gold were worked long before our ancestors were able to locate and exploit natural copper outcroppings, therefore beating copper to the historical punch. That seems to miss the point, though; figuring out how to fashion gold decorations and iron trinkets doesn’t seem like building the foundations for industry. Learning to make tools from copper, either pure or alloyed with tin to make bronze? Now that’s how you build an industrial base.

So now comes the time for us to make the case for our most recent addition to humanity’s stable of industrial metals: titanium. Despite having been discovered in 1791, titanium remained locked away inside abundantly distributed ores until the 1940s, when the technological demands of a World War coupled with a growing chemical prowess and command of sufficient energy allowed us to finally wrest the “element of the gods” from its minerals. The suddenness of it all is breathtaking, too; in 1945, titanium was still a fantastically expensive laboratory oddity, but just a decade later, we were producing it by the (still very expensive) ton and building an entirely new aerospace industry around the metal.

In this installment of “Mining and Refining,” we’ll take a look at titanium and see why it took us over 11,000 years to figure out how to put it to work for us.

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