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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.

📡 https://w7txt.net/
🐧 https://blog.namei.org/
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jmorris

James Morris

Reply to @jmorris
Edited 1 year ago
Here's a trace of the power up sequence, with the gate voltage at the top, and drain at the bottom. I'm not sure if the CRO is fast enough to catch the sequence correctly, because I can't tell if there's a gap between gate & drain. IIUC, the negative regulator chip provides a 'voltage ok' signal that is used to switch the gate, so it should be ok. But, I'll keep investigating until I'm sure.

This is the kind of thing that leads to long development times for amateur microwave radio projects, so many (fascinating) rabbit holes and a lot of learning as you go. I wonder if more people knew about this aspect of the hobby, whether we'd see more and younger people joining.
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jmorris

James Morris

Reply to @jmorris
Load testing the bias power supply. The amp uses an expensive ($650) GaN transistor which must have bias applied before main power, or it will be destroyed - it’s ‘on’ by default and needs bias to switch ‘off’. I’m being extra careful with this, will also verify the power up sequence on a scope, response to short circuit etc.
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jmorris

James Morris

Working on a 10 GHz power amp. #hamradio #amateurradio #electronics #microwave
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jmorris

James Morris

Edited 1 year ago
Just a warning for people thinking about getting into #microwave #amateurradio -- it's an infinite labyrinth of hobbies, knowledge, and equipment. Precision machining, stripline circuits, strange semiconductors (IMPATT diode amplifier, anyone?), exotic electron tubes (which will try and kill you via xrays, lethal voltages, and beryllium oxide), metrology, physics, DIY, vintage equipment resurrection, morse code (modulation? sheer luxury!), scouring ebay, haunting electronics stores, poring over poorly scanned service manuals from defunct companies, and too many hex keys.

Oh, and it's a gateway drug to #radioastronomy.

#hamradio
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jmorris

James Morris

Reply to @jmorris
Now using aluminum extrusions to adjust the position of the sensor & also hold it tight. Any further improvement will require a dial indicator to ensure it’s centered. And maybe some shims. Learning a lot about precision metalwork with this.
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jmorris

James Morris

Making some hopefully final mods to the azimuth sensor for this az/el drive. Spent ages trying to find screws to match the Hammond enclosure. Turns out to be M3.5, which I have never seen used before. #hamradio #amateurradio #microwave #radioastrnomy
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jmorris

James Morris

TIL my 50 MHz scope is still somewhat usable up to 150 MHz.
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jmorris

James Morris

Reply to @jmorris
2 hours later…
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jmorris

James Morris

It ain’t much, but it’s honest work. Az/El sensors serial (SSI) to Arduino board. Removed an RS485 layer.
@adafruit 1/4 size proto boards are cute.
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jmorris

James Morris

Reply to @jmorris
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.
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jmorris

James Morris

Edited 1 year ago
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
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jmorris

James Morris

Performed some more mm-wave testing at the PNW Microwave build day, looking at the output of the 40-50 GHz quadrupler. Thanks to W7GLF for bringing in his spectrum analyzer & external mixer. Results forthcoming.


#amateurradio #hamradio #microwave #mmwave #electronics
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jmorris

James Morris

Testing a Ka band LNB, specified for 20.2-21.2 GHz. I could not see any signals beyond 22.8 GHz (well short of the 24 GHz amateur band), but that could be due to issues at the IF level. Worth investigating further. I was able to see a good signals at 22.2, an important radio astronomy frequency. #amateurradio #microwave #radioastronomy
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jmorris

James Morris

Edited 1 year ago
Just received this in gmail. Seems like my ad blocker and/or ublock origin is working well here to stop them tracking my behavior. I have in fact been opening their emails. UbO for the email shows dozens of blocked requests to play.google.com and other related sites.
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jmorris

James Morris

Current non-fiction reading pile.
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jmorris

James Morris

It’s not everyday you get to touch an SR-71. It didn’t quite feel like metal, the paint seems to dampen it?
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jmorris

James Morris

Edited 1 year ago
Got distracted working on slides, used the AI in powerpoint to make some alien cities. Here's one on an accretion-disk world. The "water" is not for swimming.
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jmorris

James Morris

At Linux Plumbers, toolchain track. @linuxplumbersconf
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jmorris

James Morris

Reply to @jmorris
I now have a LOVELY combination of C and C++ to clean up one day.
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jmorris

James Morris

Working on some long-needed updates to my 1.2m dish setup. Mounting an azimuth sensor (ETS25 absolute encoder) directly under the Az slew drive. A previous belt-driven version was too complicated. This is all upside down, btw. #amateurradio #hamradio #radioastronomy #electronics #microwave
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