@jmorris@social.kernel.org
@jmorris@social.kernel.org avatar

jmorris

@jmorris@social.kernel.org

Linux Kernel security developer, working for Microsoft. Also W7TXT. Views are my own. Topics: #Linux #kernel #security, #amateurradio, #RF, #hamradio, #electronics, #science, #radioastronomy, #physics, #space, #arduino.

๐Ÿ“ก https://w7txt.net/
๐Ÿง https://blog.namei.org/
โ˜ ๏ธ https://www.facebook.com/w7txt

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jmorris, to random
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Videos from LSS-NA 2024 in Seattle are now up: https://www.youtube.com/playlist?list=PLbzoR-pLrL6rbN7fu5TId8VWAC5A8v5O7

jmorris, to random
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Finally learning to mill, in a work makerspace. This is a game changer for all kinds of projects. My first task is smoothing out a copper heat spreader, which was extruded and less than ideal for heat transfer.

jmorris,
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@mcdanlj flycutting is probably not the worst? It's what I needed first. Luckily, there was a good Tormach flycutter laying around, as I have no idea how to grind the Grizzly one I bought. I will do another face prep of a heatsink (Alu) before then trying to do end milling. I may start with wood or wax there.

This is addictive -- I'm actively resisting buying a bench mill because I don't have the space and I can use the one at work, but I will crack at some point and make the room. LMS & PM seem to have good starter gear, and I've already learned about avoiding round columns from this Jet.

jmorris, to fediverse
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It's been a while since I looked into different #fediverse clients. Is there a good threaded web based client, or cross-platform app?

azonenberg, to random
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Trigger crossbar board shipped before CNY fab shutdown! Hoping it gets out of China before all of the FedEx staff leave for vacation.

Stencil is already here, parts should be coming in the next day or two and should arrive before the PCB.

This will be a fun design to bring up.

jmorris,
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@azonenberg @rgilton as a hobbyist, it's interesting to see concrete costs of professional level development. I just got 3 copies of a prototype board made by @oshpark for $8, including shipping.

jmorris,
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@azonenberg @oshpark @rgilton and this is why specialized technology is expensive, which I think many people don't understand

jmorris, to hamradio
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Finished making a thing. This is a power supply for the 30W 10 GHz amplifier Iโ€™m working on. It should also be able to power the transverter, IF radio, & relays. Iโ€™m resisting the temptation to add an MCU and display. For now.

(Note: the 50 Hz label should say 60 Hz)

jmorris,
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Using green wire for ground because the USA uses black for mains hot (active). I try and do this here when AC & DC are in the same enclosure. In Australia, brown is active and blue is neutral.
Also, fwiw, mains voltage here is supplied to homes as 240v, split into 120+120, neutral is centre tapped. It is not 110, 115, or whatever else you see: itโ€™s 120v. Heavy duty appliances typically have 240v supplies, and some people run 240v to an outlet in the garage.

jmorris,
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Also, re US vs .au, the way people talk about mains phases in the home can be confusing. Each 120v supply is called a phase, whereas if you have two 240v phases in .au, it's from a 3-phase feed. The 3-phase power I've seen in a person's garage here was 480v, which is getting well into catastrophic arc flash territory (search it up on youtube for an exciting time). People here very often do their own mains wiring mods, which is extremely unusual in Australia, I suspect in part because the default 240v is often lethal. Expect to die if you touch it.

jmorris, to hamradio
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Just tripped across this blast from the past: my first published article, in an .au electronics magazine.

Remember paper magazines? No? Ok.

#hamradio #amateurradio #satellite #electronics

jmorris,
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From the same era, when writing a GUI app in Linux probably meant buying a shelf full of X programming books. I was really, really, into satellites.

jmorris,
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@penguin42 Yep, that may have been a commercial library for Linux, before an open source equivalent existed. Prior to that I was using Xwt and even raw X. The later releases of various open source GUI libraries and desktops was such an major breakthrough at the time.

jmorris,
@jmorris@social.kernel.org avatar

@penguin42 kernel programming was no more difficult

Gina, to Travel
@Gina@fosstodon.org avatar

Turns out New Zealand is very nice! ๐Ÿฅ

I will say though, you can definitely tell there's a hole in the ozone layer here. I've never felt the sun burn me to a crisp within minutes.

#travel #newzealand #coromandel #thesunisadeadlylaser

Chilling with my tea and enjoying the ocean view from my cabin
Viewpoint overlooking the other side of Coromandel
Hot water beach, where you can dig in the sand and hot water comes out, supercool

jmorris,
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@Gina yes, you will get burned in 10-15 mins even through car windows.

penguin42, to random
@penguin42@mastodon.org.uk avatar

energy quiz: You replace a 58W Fluorescent tube (5200lm nominal) by two sets of 3x 8W/1100lm LED bulbs, with each set switched separately. How much energy do you save?
One set is placed directly over the main table.
Known unknowns:
a) How much does a florescent fitting take with that tube?
b) How much light does either combination actually give?
c) Will we turn both sets on or just one most of the time?

jmorris,
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@penguin42 also, power factor.

g4dbn, to random
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jmorris,
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@g4dbn @azonenberg the possibilitiesโ€ฆ! Iโ€™m interested to know if you will be able to do very small runs of custom uwave & mmWave plumbing for amateur use.

jmorris,
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@g4dbn @azonenberg those dishes should be well-sized for for > 100 GHz, especially with good surface RMS and feed accuracy. btw, something that would be broadly useful are matching plates for common Ku band satcom feed horns with a circular waveguide connection, to wr75 or wr90.

jmorris,
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@azonenberg @g4dbn btw, there is a microwave group in the Seattle area: https://pnw-microwave.com/

jmorris, to hamradio
@jmorris@social.kernel.org avatar

After many hours, including re-capping the power supply (no dice, but worthwhile in any case), and tracing through most of the upper section, I finally found the issue with this Tektronix spectrum analyzer. A tantalum cap on the horizontal storage board failed and shorted the +15v bus. Replaced it and the SA seems to be working ok so far. #hamradio #amateurradio #electronics

jmorris, to random
@jmorris@social.kernel.org avatar

@mcdanlj I'd read that spiral flute taps are weaker and more likely to break for small taps, so I haven't tried them yet. Thanks for the pointers!

RE: https://social.makerforums.info/users/mcdanlj/statuses/111060149655556379

jmorris,
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@mcdanlj a mill would be great but I currently have no room for one. Btw, I ended up brute force drilling the broken taps out with a solid tungsten carbide bit (which broke twice), then I was able to drill & tap for 6-32. There was enough slack in the copper spreader to handle some misalignment. The rest of the 4-40 were done very carefully with a form tap and tap magic. Iโ€™ll try the spiral flute next.

jmorris, to hamradio
@jmorris@social.kernel.org avatar

Metalwork for the linear amp is going GREAT. First I drilled the wrong hole sizes for the heat sink, then broke two 4-40 taps. Will figure out how to extract these then try a thread forming tap instead of a cutting tap.

#hamradio #amateuradio #electronics

jmorris,
@jmorris@social.kernel.org avatar

@mcdanlj I hadn't heard of that method, interesting!

M0CUV, to hamradio
@M0CUV@mastodon.radio avatar

Well my PK-88 Terminal Node Controller still powers on and flashes its LEDs during boot after being in storage since the early 90s!

Now Iโ€™ve just got toโ€ฆ

A) get it connected to a #HamRadio transceiver

B) find a DB9-DB25 RS232 adapter in my old bag of serial cable kit

C) persuade lots of amateurs that they too want to recreate the 1200 baud Packet Radio network we had in the 90s before The Internet #RetroCommunications

jmorris,
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@M0CUV I tried setting up 1200 VHF packet back in 1995 or so, and it was so disappointing and painful that I did not return to digital for over 15 years.

jmorris, to random
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Wrong answers only: what does this kernel code do?

struct file *file = (struct file *)(v & ~3);

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