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GaN Fets ordered - hopefully a 1kW before 2017 !




 
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Author Topic: GaN Fets ordered - hopefully a 1kW before 2017 !  (Read 1776 times)
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steve_qix
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« on: December 21, 2016, 11:19:48 PM »

Well, I just ordered 10 of the 50A GaN MOSFETs.  Going to use 4 of them in a 1kW carrier RF amplifier (75 meters).

Hopefully, I'll have it on before the new year - we'll see how the time goes (and assuming the parts get here fairly quickly).

Should be a good project !  It'll be interesting to see how these devices behave.

Regards,

Steve
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VE3ELQ
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« Reply #1 on: December 22, 2016, 08:20:53 AM »

Excellent Steve, I'm betting they will do the job FB at 4 mhz.  LF to hearing the test results and lessons learned.
Good experimenting.

73s Nigel
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« Reply #2 on: December 31, 2016, 10:52:18 AM »

Just a few hours left.   Will class E goodness override all the 2016 bad news as of late?

:-)


--Shane
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W2PFY
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« Reply #3 on: December 31, 2016, 01:23:50 PM »

Quote
Going to use 4 of them in a 1kW carrier RF amplifier (75 meters).

So 20 of them will make 5KW? I do have a 15KVA transformer that I believe will do 100 amps at 120 volts. So that's 12,000 watts, so it could run the PDM as well? What voltage will they run at in your experiment?

I was just looking at KA1TDQ's 100 watt 40 meter E rig. It looks very easy to build much like a 75 watt single tube novice rig of yesteryear.

Steve I don't pretend to know a lot about this but thanks to your efforts and others, it getting clearer all the time.   

 
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steve_qix
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« Reply #4 on: December 31, 2016, 05:42:35 PM »

I've got an experimental rig going, but am having some problems with parasitics - need to understand where they are coming from.

Otherwise, the rig works.

More later  Smiley

Regards, Steve
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« Reply #5 on: January 02, 2017, 10:37:48 PM »

I am getting amazing efficiency out of this rig at 500 watts carrier.  The TOTAL drive power for all 4 devices is a whopping 10 watts and that is the total power INPUT to all drivers on 75 meters.

The heat sink does not get warm (at 500 watts drain input).  Have not run at a kw yet.

The next step is a big one - I definitely have layout issues with my JS quickie layout.  I am going to rebuild the rig with a proper layout and repeat all of the tests.

Will report back!

Regards,  Steve
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« Reply #6 on: January 03, 2017, 08:38:31 AM »

Good stuff Steve, sounds like you are making progress.  For sure these GaNs are different animals and will take some experimenting to figure them out.  Curious as to how you are driving them, what drivers and what driver voltage??  My very limited experimenting with the 17A GaNs on 20M I found anything over 8V made no performance difference just higher driver current. Also of note is the voltage rating, seems its very conservative based on MTBF so they could probably be run up to or even a bit higher than spec for short durations such as mod peaks.  Their application note explains it all in detail in case you haven't already seen it.
http://www.transphormusa.com/document/drain-voltage-avalanche-ratings-gan-fets/
Should be a great transmitter.  Please keep us updated.
73s  Nigel
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« Reply #7 on: January 03, 2017, 10:55:35 AM »

Hi Nigel - Happy new year!

I'm driving the GaN Fets with IXDD614 drivers operating at 10V, 1 driver per device.  I have not noticed a performance degradation going from 12V to 10V and the curves indicate the device is in saturation at around 8V.

Hopefully my new layout will be both easier to work with (the current layout is very crowded) and completely stable.

I'll be reporting back once the new layout is completed and running  Smiley

Also am going to experiment with a couple of different RF output transformer designs once everything is working.  Fun stuff!

Regards,  Steve
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« Reply #8 on: January 14, 2017, 10:20:52 AM »

Hi Steve,

Are there plans to update the Class E Website with build instructions using newer FETs?  I was planning on building an AM transmitter for 75/80 last year, but I held off when I was told about the new FETs coming on the market.  I've heard folks running Class E driven with a Flex Radio and they sound FB.

73,
Scott
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« Reply #9 on: January 15, 2017, 11:56:32 AM »

I'm waiting for the 24 FET plans to get published.  My projects are almost done.  In about a month or so I'm going to be bored.

Jon
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« Reply #10 on: January 15, 2017, 10:30:40 PM »

My experiments with the GaN FETs are proceeding. I am having an anomaly where the class E waveform starts to come apart at very high levels of modulation with a carrier power over 500 watts.

I am trying to figure out exactly what is causing this - so far have not solved the problem.  It happens with 2 different layouts, so it's not specific to this particular test.

More later!

Hm.. I thought the plans for the 24 FET transmitter were published on the class E site.  I'll check it out.  It's a fairly straight-forward design, and a number of these have been built and are on the air.

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ka1tdq
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« Reply #11 on: January 15, 2017, 11:20:05 PM »

How did I miss that?  Seriously...

I've been to the class E website a thousand times, and I thought that the 24 FET rig was a secret.  Apparently I'm not reading all the instructions. 

Anyway, I did find it and it looks awesome!  I now know what's going to go in that steel cabinet I just got. 

I'll open up a new thread once I get the parts collected.  Semiconductors alone for this will definitely require some overtime at work.

Jon
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