James Morris
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349📡 https://w7txt.net/
🐧 https://blog.namei.org/
☠️ https://www.facebook.com/w7txt
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.
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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: it’s 120v. Heavy duty appliances typically have 240v supplies, and some people run 240v to an outlet in the garage.
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: it’s 120v. Heavy duty appliances typically have 240v supplies, and some people run 240v to an outlet in the garage.
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James Morris
jmorris
Edited 1 year ago
Finished making a thing. This is a power supply for the 30W 10 GHz amplifier I’m working on. It should also be able to power the transverter, IF radio, & relays. I’m resisting the temptation to add an MCU and display. For now.
(Note: the 50 Hz label should say 60 Hz)
#hamradio #electronics #amateurradio #microwave #qro #sspa
(Note: the 50 Hz label should say 60 Hz)
#hamradio #electronics #amateurradio #microwave #qro #sspa
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Ok, I think I understand this a little more now. The horizontal bar in the waveguide is a thermal mass, which heats up in the presence of RF. The detector thermistor is attached to it (too small to see here), and it will closely follow the temperature of the bar. A bias current runs through the thermistor, and also the isolated compensation thermistor. The comp thermistor has its own thermal mass, which is the gold plated square, and a couple of rectangular blocks, which I assume were selected and pasted in by hand during construction, and this can be finely adjusted via the screw. Not sure exactly where the compensation thermistor is yet, and the circuit diagram shows a capacitor here somewhere. Could be both are in the white block, which looks like a modern SMD cap.
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James Morris
jmorris
Edited 1 year ago
Not sure if this microwave power sensor is repairable. It’s an HP P486A waveguide thermistor mount for 12.4 to 18 GHz. It was bugging out, and I’ve rejuvenated one of these before (using the guidelines in the manual) but it didn’t work this time. I’m puzzled by the mechanics of this, what the adjustment screw actually does, and why is it attached to a small metal block which is maybe held with conductive paste? It’s supposed to finely match the inner and outer thermistors: one is in the waveguide and the other is inside the housing as a reference. The waveguide thermistor is heated by the RF signal, and the power meter detects this, via a bridge circuit which tries to balance the current in each thermistor.
The wonders of 1960s microwave tech. We explored space with this stuff.
#hamradio #amateurradio #microwave #electronics
The wonders of 1960s microwave tech. We explored space with this stuff.
#hamradio #amateurradio #microwave #electronics
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James Morris
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Jeroen Baert
jbaert@mastodon.socialCrazy read: detecting positions of players in Counterstrike by *listening to their GPU over a microphone*
https://faculty.cc.gatech.edu/~genkin/papers/lendear.pdf
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James Morris
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keithp
keithp@fosstodon.orgReleased picolibc version 1.8.6 today.
Highlights: ctype avoids a static array, fenv functions are inlined (except on x86).
Full release notes here: https://github.com/picolibc/picolibc/releases/tag/1.8.6
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James Morris
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Linux Security Summit 🐧
LinuxSecSummit
❕ 📢 Note: The LSS-NA 2024 CfP has been EXTENDED ❕
🐧 The new CfP deadline is: Sunday, February 4 at 11:59 PM PST
🐧 For full details, see
https://events.linuxfoundation.org/linux-security-summit-north-america/program/cfp/
RE: https://social.kernel.org/objects/a91fa775-15d9-4ee0-bc99-f9b40cad10c5
🐧 The new CfP deadline is: Sunday, February 4 at 11:59 PM PST
🐧 For full details, see
https://events.linuxfoundation.org/linux-security-summit-north-america/program/cfp/
RE: https://social.kernel.org/objects/a91fa775-15d9-4ee0-bc99-f9b40cad10c5
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Evil Mad Scientist
emsl@mastodon.cloudAnnouncing the acquisition of Evil Mad Scientist by Bantam Tools.
Dr. Windell Oskay & Lenore Edman will be joining as CTO and COO of Bantam Tools in Peekskill NY.
Pen plotter enthusiasts can look forward to a new generation of art machines in Spring 2024.
More at: https://www.evilmadscientist.com/2024/bantam-tools/
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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.
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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James Morris
jmorris
@MLE_online tell me you're not in the PNW right now without telling me...
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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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