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Newfangled Class E parts




 
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Author Topic: Newfangled Class E parts  (Read 3204 times)
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KF1Z
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Are FETs supposed to glow like that?


« on: December 11, 2020, 12:29:04 PM »

So.......
I've been out of the loop for ... too long .....

I'm assuming by now, new mosfets, gate drivers, etc have been 'discovered'

maybe even whole new methods...

Hoping to drag the old pwm modulator and class-e RF deck out of storage...
But after the past 7-8 years of being moved across the country twice, and 1/2 way once
being mistreated in storage etc.. not sure any of it's is going to fire up.
( that is if I can remember how to operate it  Cheesy )

So may have to start from scratch with some of it.

Carry on
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KQ6F
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« Reply #1 on: December 11, 2020, 02:28:31 PM »

Well, they're not exactly new but the SiC FETs from CREE may have come on the scene while you were gone.  I've had very good luck with the C2M0160120D devices.  Very robust.  Also Nigel VE3ELQ reported good results with the 900-volt device in the same family.

Rod
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M0VRF
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« Reply #2 on: December 12, 2020, 05:46:00 AM »

Yes the Cree SiC devices are very good, check their line up. Also the GaNs from Transphorm are very good and much easier to drive. No need for those huge drivers, the NCP81074As are fine for all devices. Hardly newfangled tho' and been around for years!
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vk3alk
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« Reply #3 on: December 12, 2020, 11:35:05 PM »

Hi Bruce....

Time has slipped by quickly..... 7 years woooww ...

Those nice Transmitters you built I would just apply power and see what happens.....
Test each Module separately and they might just work fine  Grin

The odd twink here and there and away you go ..........


Wayne

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steve_qix
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« Reply #4 on: December 13, 2020, 11:54:23 PM »

Hi Bruce, good to hear from you on the forum !!!

I'm trying to remember what you had.  I think your modulator is a PWM unit, in which case it should be fine just as it is.  You'll need to remember (or figure out) what is the specified load impedance (resistance) for the modulator (PWM filter).  How many MOSFETs are in the RF amplifier, and is it analog drive or digital drive?

For 75 and 160 meters, the standard MOSFETs (FQA11N90s at al) are still the most *reliable* option.

The SiC devices are very interesting, and I have personally built several RF amplifiers using them, however, due to the small die size and other factors, the SiC devices are VERY sensitive to overloads, and the SOA curve shows that any overload must be of an extremely short duration (much shorter than a standard MOSFET can withstand), or the internal structure of the device will be destroyed.

The IXDD414 has been replaced by the IXDD614.  It is functional on 160 and 80 meters for sure.  IMHO, it is not as good a driver as the IXDD414, however it does work almost as well, and many people have built successful and reliable class E transmitters using the IXDD614.

Are you still out in the West, or are you closer to the North East these days?

Good to hear from you again after all these years.

Steve
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High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
vk3alk
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« Reply #5 on: December 14, 2020, 07:18:35 AM »

Actually there is something weird about the IXDD614....

It definitely isn't the same the IXDD414 and unfortunately now only have the 614s left......

It seems with some only...  that when the Vcc voltage is more then twice the input voltage there is no output.....

The way around was to provide a little DC bias and all works well .... Roll Eyes

The IXDD414 only needed 3 volts input appox and away it went.....


Wayne
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KF1Z
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Are FETs supposed to glow like that?


« Reply #6 on: December 15, 2020, 11:28:56 AM »

Steve,

We spent 4 years in the high desert of Nevada, then the last 3 years in
North Central Washington....
I'm now down in Virginia... Closer to the Northest,
hence my renewed interest in getting back on the air.

Yes, I have the PWM modulator.
And a couple different RF decks.

The bigger one was the 8 Fet ( 2x4)
And a smaller one I was playing with thats 2x2

Yes impedance, I think the larger was 5 ohms? ( or 8 ?)

Digital drive for both, however, I dont think I have a VFO anymore.
So that will have to happen.

Been digging through remaining boxes, and a little dismayed at what I dont seem to have anymore.

I do have a bunch of IXDD414 ( and some 614 ) ,  ATC caps, and FETs

So I should be good to repair/rebuild the RF decks.

Need to clear off some bench space, and see what I can figure out.,
Currently, all my work space is cluttered with 3D printer parts.
As that has consumed most of my time for the past 3-4 years.
( repairing/ refurbishing for a Chinese company)

Still need to get some copper in the air, but have been listening to the K3FEF web sdr off and on.


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steve_qix
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« Reply #7 on: December 24, 2020, 06:35:32 PM »

Actually there is something weird about the IXDD614....

It definitely isn't the same the IXDD414 and unfortunately now only have the 614s left......

It seems with some only...  that when the Vcc voltage is more then twice the input voltage there is no output.....

The way around was to provide a little DC bias and all works well .... Roll Eyes

The IXDD414 only needed 3 volts input appox and away it went.....


Wayne

Wow, THAT'S a bug !
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High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
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