James Morris
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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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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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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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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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Paul Moore
securepaul@fosstodon.orgSELint, a linter for SELinux policy sources, released a new version yesterday: SELint v1.5.
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@jtfletchbot btw, the PCB and housing is from Lothar Baier, https://texasmicrowave.com/ . Saves a mountain of busywork for me.
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@jtfletchbot I believe it can produce more linear power with higher voltage and aggressive cooling, but 25W will be a good start.
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James Morris
jmorris
@jtfletchbot this is for a TGA2623-CP device (yet to arrive), with the aim of 25W out for about 60mW in.
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