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   James Morris (jmorris@social.kernel.org)'s status on Tuesday, 09-Jan-2024 13:51:38 JST James Morris
   Working on a 10 GHz power amp. #hamradio #amateurradio #electronics #microwave
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     James Morris (jmorris@social.kernel.org)'s status on Thursday, 11-Jan-2024 03:48:24 JST James Morris

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     • Josh KD2YGL
     @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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     Josh KD2YGL (jtfletchbot@mastodon.hams.social)'s status on Thursday, 11-Jan-2024 03:48:31 JST Josh KD2YGL

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     @jmorris What's the input and output wattage? If you don't mind my asking.

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     James Morris (jmorris@social.kernel.org)'s status on Thursday, 11-Jan-2024 03:50:32 JST James Morris

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     • Josh KD2YGL
     @jtfletchbot I believe it can produce more linear power with higher voltage and active cooling, but 25W will be a good start.
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     James Morris (jmorris@social.kernel.org)'s status on Thursday, 11-Jan-2024 03:54:08 JST James Morris

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     • Josh KD2YGL
     @jtfletchbot btw, the PCB and housing is from Lothar Baier, https://texasmicrowave.com/ . Saves a mountain of busywork for me.
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     Josh KD2YGL (jtfletchbot@mastodon.hams.social)'s status on Thursday, 11-Jan-2024 05:09:30 JST Josh KD2YGL

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     @jmorris That's very cool! I wish you luck in your endeavors!

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     James Morris (jmorris@social.kernel.org)'s status on Monday, 15-Jan-2024 05:23:15 JST James Morris

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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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     James Morris (jmorris@social.kernel.org)'s status on Tuesday, 16-Jan-2024 05:44:37 JST James Morris

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     I suspect my CRO is not fast enough to catch the gap between gate (top trace) and drain (bottom trace) when powered up. Or I don’t know how to use it properly. In any case, I will keep at it, until I know for sure that this will not kill the GaN transistor. Also, this is why it takes so long to get up and running on microwave radio, so many rabbit holes, and why it’s interesting (to me).
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     James Morris (jmorris@social.kernel.org)'s status on Tuesday, 16-Jan-2024 05:55:44 JST James Morris

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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.
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     James Morris (jmorris@social.kernel.org)'s status on Tuesday, 16-Jan-2024 05:59:34 JST James Morris

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     of course, now I have run out of SMD caps
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     Gary @N8DMT (n8dmt@mastodon.radio)'s status on Wednesday, 17-Jan-2024 11:39:24 JST Gary @N8DMT

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     @jmorris Analog Devices makes voltage sequencers for turn on and turn off control. Digikey has an overview article to help designers get started. Have found turn-off to be a bigger challenge than turn-on…

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