amateur radio - Hackaday

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Hackaday Links: May 23, 2021

Posted: 23 May 2021 04:00 PM PDT
https://hackaday.com/2021/05/23/hack...s-may-23-2021/


The epicenter of the Chinese electronics scene drew a lot of attention this
week as a 70-story skyscraper started wobbling in exactly the way
skyscrapers shouldnt. The 1,000-ft (305-m) SEG Plaza tower in Shenzhen
began its unexpected movements on Tuesday morning, causing a bit of a panic
as people ran for their lives. With no earthquakes or severe weather events
in the area, theres no clear cause for the shaking, which was clearly
visible from the outside of the building in some of the videos shot by
brave souls on the sidewalks below. The preliminary investigation declared
the building safe and blamed the shaking on a combination of wind,
vibration from a subway line under the building, and a rapid change in
outside temperature, all of which wed suspect would have occurred at some
point in the 21-year history of the building. Others are speculating that a
Kármán vortex Street, an aerodynamic phenomenon that has been known to
catastrophically impact structures before, could be to blame; this seems a
bit more likely to us. Regardless, since the first ten floors of SEG Plaza
are home to one of the larger electronics markets in Shenzhen, we hope this
is resolved quickly and that all our friends there remain safe.

In other architectural news, perched atop Building 54 at the Massachusetts
Institute of Technology campus in Cambridge for the last 55 years has been
a large, fiberglass geodesic sphere, known simply as The Radome. Its
visible from all over campus, and beyond; we used to work in Kendall
Square, and the golf-ball-like structure was an important landmark for
navigating the complex streets of Cambridge. The Radome was originally used
for experiments with weather radar, but fell out of use as the technology
it helped invent moved on. That led to plans to remove the iconic
structure, which consequently kicked off a Save the Radome campaign. The
effort is being led by the students and faculty members of the MIT Radio
Society, who have put the radome to good use over the years it currently
houses an amateur radio repeater, and the Radio Society uses the dish
within it to conduct Earth-Moon-Earth (EME) microwave communications
experiments. The students are serious they applied for and received a
$1.6-million grant from Amateur Radio Digital Communications (ARDC) to
finance their efforts. The funds will be used to renovate the deteriorating
structure.

Well, this looks like fun: Python on a graphing calculator. Texas
Instruments has announced that their TI-84 Plus CE Python graphing
calculator uses a modified version of CircuitPython. Theyve included seven
modules, mostly related to math and time, but also a suite of TI-specific
modules that interact with the calculator hardware. The Python version of
the calculator doesnt seem to be for sale in the US yet, although the UK
site does have a few where to buy entries listed. Itll be interesting to
see the hacks that come from this when these are readily available.

Did you know that PCBWay, the prolific producer of cheap PCBs, also offers
3D-printing services too? We admit that we did not know that, and were
therefore doubly surprised to learn that they also offer SLA resin
printing. But whats really surprising is the quality of their clear resin
prints, at least the ones shown on this Twitter thread. As one commenter
noted, these look more like machined acrylic than resin prints. Digging
deeper into PCBWays offerings, which not only includes all kinds of 3D
printing but CNC machining, sheet metal fabrication, and even injection
molding services, its becoming harder and harder to justify keeping those
capabilities in-house, even for the home gamer. Although with what weve
learned about supply chain fragility over the last year, we dont want to
give up the ability to make parts locally just yet.

And finally, how well-calibrated are your fingers? If theyre just right,
perhaps you can put them to use for quick and dirty RF power measurements.
And this is really quick and really dirty, as well as potentially really
painful. It comes by way of amateur radio operator VK3YE, who simply uses a
resistive dummy load connected to a transmitter and his fingers to monitor
the heat generated while keying up the radio. He times how long it takes to
not be able to tolerate the pain anymore, plots that against the power
used, and comes up with a rough calibration curve that lets him measure the
output of an unknown signal. Its brilliantly janky, but given some of the
burns weve suffered accidentally while pursuing this hobby, wed just as
soon find another way to measure RF power.