What does a Harley-Davidson motorcycle have to do with building antennas? Absolutely nothing, unless you happen to have one and need to work-harden copper wire to build a collinear antenna for LoRa.
We’ll explain. Never being one to settle, [Andreas Spiess] needed a better antenna for his LoRa experiments. Looking for high gain and an omnidirectional pattern, he bought a commercial colinear antenna, which is a wire with precisely spaced loops that acts like a stack of dipoles. Sadly, in a head-to-head test [Andreas] found that the commercial antenna was no better than lower gain antennas in terms of range, and so he decided to roll his own.
Copper wire is a great material for antennas since it can be easily formed without special tools and it solders like a champ. But the stuff you get at the home center is nowhere near stiff enough for a free-standing vertical whip. This is where the Harley came in: [Andreas] used his Hog to stretch out the 1.75-mm diameter (a little bigger than #14 AWG) copper wire. Not only did the work-hardening stiffen the wire, it reduced its diameter to the 1.4 mm needed for the antenna design. His vector network analyzer told him that ground-plane elements and a little fiddling with the loop diameter were needed to get the antenna to resonate at 868 MHz, but in the end it looks like the antenna is on track to deliver 5-dBi of gain.
Of course there are plenty of other ways to stretch out a wire — you could just stretch it out with hanging weights, or even with a go-kart motor-powered winch if you’re ambitious. But if you’ve got a bike like that, why not flaunt it?
Continue reading “Harley-Hardened Wire Helps High-Gain Antenna Hack”
If you are a lover of motorcycling, you’ll probably fit into one or other of the distinct groups of riders. Maybe you’re a sportsbike lover always trying to get your knee down, a supermotard who gets their knee down without trying, a trailie rider for whom tarmac is an annoyance between real rides, or a classic bike enthusiast who spends more time in the workshop than riding.
[Xavier Morales] is none of these, for he cruises the roads of his native Catalonia on a Harley-Davidson Sportster. If you’re familiar with Harleys only from popular culture, or you’re a sportsbike rider who derides them for anachronistic handling and brakes, it’s worth taking a look at a modern Harley from a technical standpoint. Despite styling and brand ethos that evokes another era with the trademark large V-twin engine that looks to the untrained eye the same as it did decades ago, today’s Harley is a very modern machine, and much more capable than the sneering sportsbiker would give it credit for.
There is one area though in which [Xavier]’s Harley was sorely lacking. Its single instrument was a speedometer, it had no rev counter. You might think this would be less of an issue with the lower-revving Harley engine than it would be with a Japanese sportsbike that exists in a hail of revs, but it was annoying enough to him that he built his own tachometer. His write-up of the project is both lengthy and fascinating, and well worth a read.
The Sportster’s data bus follows an established but obsolete standard, SAE J1850 VPW. Since driver chips for this bus are out of production, he had to create his own using a transistor and a couple of resistors. Once he has the data he feeds it to a PIC 18F2553 which in turn runs a display driver chip controlling a brace of 7-segment LEDs. There are also a set of LEDs to indicate gear changes. The whole is installed in a 3D-printed housing alongside the original speedometer, behind the glass from another dial. As a result it looks as though the bike was always meant to be a two-clock design, with a professional appearance.
If you’d like to see it in action, he’s posted a few videos, and we’ve put one below the break. The beautiful Catalan scenery and the mountain twisties look very inviting.
Continue reading “A Digital Tacho For A Harley”