A Hybrid Helical Antenna For The Es’hail-2 Geosynchronous Repeater

Amateur radio operators like to say that working a contact in space can be done with a simple handheld transceiver and a homemade antenna. And while that’s true, it’s true only for low Earth orbit satellites such as the ISS. If you want to reach a satellite in geosynchronous orbit it’ll take a little more effort, and this dual-feed helical “ice cream cone” antenna could really help.

Until recently, the dream of an amateur radio repeater in geosynchronous orbit remained out of reach, but that changed with the launch of the Qatari satellite Es’hail-2 last year. Since then, hams from Brazil to Thailand have been using the repeater, and UK-based [Tech Minds] has been in the thick of the action. The antenna he presents is a hybrid design, needed because of the 2.4-GHz band uplink and 10-GHz downlink on the satellite, also known as QO-100. Both require a largish dish antenna, with the downlink requiring a low-noise block downconverter (LNB) and feed horn. The uplink side of [Tech Minds]’ antenna is a helical design, with three-and-a-half turns of heavy copper wire and a tuning section of copper strapping that attaches directly to an N-type connector. The helix is just the right size for the feed horn of an LNB for the downlink side, nestled in a hole in the helical antenna’s aluminum reflector disc. There are 3D-printed parts to support everything, plus a cone-shaped radome to keep it all safe from the elements.

It looks like a great design, but sadly, North American and East Asian hams can only dream about building one, since QO-100 is below the horizon for us. We’re jealous, but we’re still glad the repeater is up there. Check out this article for more on how Es’hail-2 got the first geosynchronous ham repeater.

Continue reading “A Hybrid Helical Antenna For The Es’hail-2 Geosynchronous Repeater”

3D Print Springs With Hacked GCode

If you’ve used a desktop 3D printer in the past, you’re almost certainly done battle with “strings”. These are the wispy bits of filament that harden in the air, usually as the printer’s nozzle moves quickly between points in open air. Depending on the severity and the material you’re printing with, these stringy interlopers can range from being an unsightly annoyance to triggering a heartbreaking failed print. But where most see an annoying reality of pushing melted plastic around, [Adam Kumpf] of Makefast Workshop sees inspiration.

Noticing that the nozzle of their printer left strings behind, [Adam] wondered if it would be possible to induce these mid-air printing artifacts on demand. Even better, would it be possible to tame them into producing a useful object? As it turns out it is, and now we’ve got the web-based tool to prove it.

As [Adam] explains, you can’t just load up a 3D model of a spring in your normal slicer and expect your printer to churn out a useful object. The software will, as it’s designed to do, recognize the object can’t be printed without extensive support material. Now you could in theory go ahead and print such a spring, but good luck getting the support material out.

The trick is to throw away the traditional slicer entirely, as the layer-by-layer approach simply won’t work here. By manually creating GCode using carefully tuned parameters, [Adam] found it was possible to get the printer to extrude plastic at the precise rate at which the part cooling fan would instantly solidify it. Then it was just a matter of taking that concept and applying it to a slow spiral motion. The end result are functional, albeit not very strong, helical compression springs.

But you don’t have to take their word for it. This research has lead to the creation of an online tool that allows you to plug in the variables for your desired spring (pitch, radius, revolutions, etc), as well as details about your printer such as nozzle diameter and temperature. The result is a custom GCode that (hopefully) will produce the desired spring when loaded up on your printer. We’d love to hear if any readers manage to replicate the effect on their own printers, but we should mention fiddling with your printer’s GCode directly isn’t without its risks: from skipping steps to stripped filament to head crashes.

The results remind us somewhat of the 3D lattice printer we featured a couple of years back, but even that machine didn’t use standard FDM technology. It will be interesting to see what other applications could be found for this particular technique.

Continue reading “3D Print Springs With Hacked GCode”

Mechanisms: Couplings

I was splitting wood one day a few years back, getting next winter’s firewood ready on my hydraulic splitter. It normally handled my ash and oak with ease, but I had a particularly gnarly piece of birch queued up, and the splitter was struggling. The 20-ton cylinder slowed as the wedge jammed in the twisted grain, the engine started to bog down, then BANG! I jumped back as something gave way and the engine revved out of control; I figured a hydraulic hose gave out. Whatever it was, I was done for the day.

I later discovered that a coupler between the engine shaft and the hydraulic pump failed dramatically. It was an easy fix once I ordered the right part, and I’ve since learned to keep extras in stock. Couplings are useful things, and they’re the next up in our series on mechanisms.

Continue reading “Mechanisms: Couplings”

Jump In When The Water Is Just Right With A Wireless Swimming Pool Thermometer

[David]’s family acquired a swimming pool. While it’s not his favorite activity in the world, every now and then he’ll indulge in the blue plastic bin full of water occupying previously pristine land in his backyard.

As he says, cool beer is pleasant, but cool water tends to put a damper on the experience. Rather than do something pedestrian like touch the water himself to discover its temperature; he saw an opportunity for a fun little project in a wireless temperature monitor.

The heart of the device is a Telecom Design TD1208 which runs on the French SigFox network. For a small fee any device on the network can send up to 140 12byte packets of data a day. Not a lot, but certainly acceptable for the Microchip MCP9700 temperature sensor it uses. He got the board up and running, and even made his own custom helical coil antenna.

The case was 3D printed out of PLA. It’s a tiered cylindrical bobber. The wider top section floats on the water and the base acts as a ballast, holding the battery and sensor.  The bobber is powered by a combination of  a questionable Chinese lithium battery, charging circuit, and solar panel. [Dave] was keen to point out that the battery is, technically, water cooled.

He wrapped up the code for the bobber and used SigFox’s SDK to build a nice web interface. Now, when the rare mood strikes him, he can remain inside if the conditions aren’t right for a swim.