[Marcel] was trying to shoehorn a few new parts into his trusty Nexus 5 phone. If you’ve ever opened one of these little marvels up, you know that there’s not much room under the hood to work with. Pulling out some unnecessary parts (like the headphone jack) buys some space, but then how to wire it all up?
[Marcel] needed a multi-wire connector that’s as thin as possible, but he wasn’t going to go the order-Kapton-flex route. Oh no! He built one himself from masking tape and the strands from a stranded wire. Watch the video how-to if that alone isn’t enough instruction.
If you’ve worked with radios or other high-frequency circuits, you’ve probably noticed the prevalence of 50 ohm coax. Sure, you sometimes see 75 ohm coax, but overwhelmingly, RF circuits work at 50 ohms.
[Microwaves 101] has an interesting article about how this became the ubiquitous match. Apparently in the 1930s, radio transmitters were pushing towards higher power levels. You generally think that thicker wires have less loss. For coax cable carrying RF though, it’s a bit more complicated.
First, RF signals exhibit the skin effect–they don’t travel in the center of the conductor. Second, the dielectric material (that is, the insulator between the inner and outer conductors) plays a role. The impedance is also a function of the dielectric material and the diameter of the center conductor.
For some reason, communications and power infrastructure fascinates me, especially the long-haul lines that move power and data over huge distances. There’s something about the scale of these projects that really gets to me, whether it’s a high-tension line marching across the countryside or a cell tower on some remote mountain peak. I recently wrote about infrastructure with a field guide that outlines some of the equipment you can spot on utility poles. But the poles and wires all have to end at the shore. Naturally we have to wonder about the history of the utilities you can’t see – the ones that run under the sea.
We live under the umbrella of an intricate and fascinating web of infrastructure that enables every aspect of modern technology. But how often do we really look at it? I’ve been intrigued by utility poles for years, and I’ve picked up a thing or two that I’d like to share. Bear in mind these are just my observations from the ground in my area; I’m sure utility professionals will have better information, and regional practices will no doubt lead to very different equipment arrangements. But here’s a little of what I’ve picked up over my years as a pole geek.
In this short but intense classic of corporate cinematography, we get to watch as the Pacific Bell central office in Glendale, California is converted to electronic switching in a 47-second frenzy of cable cutting in 1984.
In the 1970s and 1980s, conversion of telephone central office (CO) switch gear from older technologies such as crossbar (XBar) switches or step-by-step (SxS) gear to electronic switching systems (ESS) was proceeding apace. Early versions of ESS were rolling out as early as the 1950s, but telcos were conservative entities that were slow to adopt change and even slower to make changes that might result in service outages. So when the time finally came for the 35,000 line Glendale CO to cutover from their aging SxS gear to ESS, Pacific Bell retained Western Electric for their “Speedy Cutover Service.”
Designed to reduce the network outage time to a minimum, cuts like these were intricately planned and rehearsed. Prep teams of technicians marked the cables to be cut and positioned them for easy access by the cutters. For this cut, scaffolding was assembled to support two tiers of cutters. It looks like the tall guys got the upper deck, and the shorter techs – with hard hats – worked under them.
At 11PM on this cut night, an emergency coordinator verified that no emergency calls were in progress, and the cut began. In an intense burst of activity, each of the 54 technicians cut about 20 cables. Smiles widened as the cut accelerated, and sparks actually flew at the 35.7 second mark. When done, each tech turned around and knelt down so the supervisors knew when everyone was done. At least one tech couldn’t help but whoop it up when the cut was done. Who could blame him? It must have been a blast.
USB has been on our desktops and laptops since about 1997 or so, and since then it has been the mainstay of computer peripherals. No other connector is as useful for connecting mice, keyboards, webcams, microcontroller development boards, and everything else; it’s even the standard power connector for phones. The latest advance to come out of the USB Implementers Forum is the USB Type-C connector, a device with gigabits of bandwidth and can handle enough current to power a laptop. It’s the future, even if Apple’s one-port wonder isn’t.
The cable of the future is, by default, new. This means manufacturers are still figuring out the port, and how to wire it up. You would think remembering ‘red = power, black = ground’ is easy, but some manufacturers get it so terribly wrong.
The cable in question was a SurjTech 3M cable that has thankfully been taken down from Amazon. Swapping GND and Vbus weren’t the only problem – the SuperSpeed wires were missing, meaning this was effectively only a USB 2 cable with a Type-C connector. The resistor required by USB spec was the wrong value, and was configured as a pull-down instead of a pull-up.
This isn’t an issue of a cable not meeting a design spec. Ethernet cables, specifically Cat6 cables, have been shown to work but fail to meet the specs for Cat6 cables. That’s shady manufacturing, but it won’t break a computer. This is a new low in the world of computer cables, but at least the cable has disappeared from Amazon.
Though we’ve never used their cables, [Blue Jeans Cable] out of Seattle, WA sure does seem to take the black art of cable manufacture seriously. When they read the Cat 6 specification, they knew they couldn’t just keep building the cables the way they used to. So they did some research and purchased a Fluke certification tester for a measly 12,000 US dollars. While they were purchasing the device, they ran across an interesting tidbit in the fluke knowledge base. Fluke said that 80% of the consumer Cat 6 cables they tested didn’t begin to meet the Cat 6 specification.
This is the part where [Blue Jeans Cable] earns our respect; like good scientists, they set out to replicate Fluke’s results. Sure enough, 80% of the Cat 6 cables they tested from big box stores etc. failed the specification. More surprising, many of them didn’t even pass the Cat 5e specification. [Blue Jeans Cable] asserts that this is possible because the Ethernet cable specification is policed via the honor system, allowing manufacturers to be fairly brazen about what they label as Cat 6.