When the news broke recently that communications had finally been re-established with Voyager 2, I felt a momentary surge of panic. I’ve literally been following the Voyager missions since the twin space probes launched back in 1977, and I’ve been dreading the inevitable day when the last little bit of plutonium in their radioisotope thermal generators decays to the point that they’re no longer able to talk to us, and they go silent in the abyss of interstellar space. According to these headlines, Voyager 2 had stopped communicating for eight months — could this be a quick nap before the final sleep?
Thankfully, no. It turns out that the recent blackout to our most distant outpost of human engineering was completely expected, and completely Earth-side. Upgrades and maintenance were performed on the Deep Space Network antennas that are needed to talk to Voyager. But that left me with a question: What about the rest of the DSN? Could they have not picked up the slack and kept us in touch with Voyager as it sails through interstellar space? The answer to that is an interesting combination of RF engineering and orbital dynamics.
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In general, you get what you pay for, and if what you pay for is a dollar-store WiFi antenna that claims to provide 12 dBi of signal gain, you shouldn’t be surprised when a rusty nail performs better than it.
The panel antenna that caught [Andrew McNeil]’s eye in a shop in Rome is a marvel of marketing genius. He says what caught his eye was the Windows Vista compatibility label, a ploy that really dates this gem. So too does the utterly irrelevant indication that it’s USB compatible when it’s designed to plug into an SMA jack on a WiFi adapter. [Andrew]’s teardown was uninspiring, revealing just a PCB with some apparently random traces to serve as the elements of a dipole. We found it amusing that the PCB silkscreen labels the thru-holes as H1 to H6, which is a great way to make an uncrowded board seem a bit more important.
The test results were no more impressive than the teardown. A network analyzer scan revealed that the antenna isn’t tuned for the 2.4-GHz WiFi band at all, and practical tests with the antenna connected to an adapter were unable to sniff out any local hotspots. And just to hammer home the point of how bad this antenna is, [Andrew] cobbled together a simple antenna from an SMA connector and a rusty nail, which handily outperformed the panel antenna.
We’ve seen plenty of [Andrew McNeil]’s WiFi antenna videos before, like his umbrella and tin can dish. We like the sanity he brings to the often wild claims of WiFi enthusiasts and detractors alike, especially when he showed that WiFi doesn’t kill houseplants. We can’t help but wonder what he thinks about the current 5G silliness.
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In a field where components and systems are often known by sterile strings of characters that manufacturers assign or by cutesy names that are clearly products of the marketing department and their focus groups, having your name attached to an innovation is rare. Rarer still is the case where the mere mention of an otherwise obscure inventor’s name brings up a complete schematic in the listener’s mind.
Given how rarely such an honor is bestowed, we’d be forgiven to think that Sidney Darlington’s only contribution to electronics is the paired transistor he invented in the 1950s that bears his name to this day. His long career yielded so much more, from network synthesis theory to rocket guidance systems that would eventually take us to the Moon. The irony is that the Darlington pair that made his name known to generations of engineers and hobbyists was almost an afterthought, developed after a weekend of tinkering.
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If you’ve hung around electronics for any length of time, you’ve surely heard of the decibel (often abbreviated dB). The decibel is a measure of a power ratio. Actually, the real measure is a bel, but you almost never see that in practice. If you are versed in metric, you won’t be surprised to learn a decibel is 1/10 of a bel. Sometimes in electronics, we deal with really large ratios, so the decibel is logarithmic to cope with this. Doubling the number of decibels doesn’t double the ratio, as you will soon see. It’s all about logarithms, and this ends up being extremely useful when measuring something like antenna or amplifier gain.
Besides antennas, decibels are often used to measure sound and light. The reason is that human ears and eyes have a logarithmic response to those quantities. Your ear, for example, has a huge dynamic range. That is to say, you can hear a whisper or a space shuttle launch. That ratio is about 1 trillion to 1, but that’s only 120 dB. This is also why potentiometers made for volume controls have a logarithmic taper. A linear pot would seem off because, for example, a tenth of a turn at one extreme will affect the apparent volume much more than a tenth of a turn at the other extreme. This holds true whether or not those knobs go up to eleven.
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