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Class E - 20 meters and higher




 
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Author Topic: Class E - 20 meters and higher  (Read 1922 times)
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kb3ouk
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« on: March 30, 2016, 09:41:02 PM »

I see all kinds of development on transmitters that cover 160, 80, and 40 meters, but don't see much on anything for 20, 15, or 10. I know there are commercial class E designs that work at 13.56 mhz and also some that I believe operate up in the 26-27 mhz range, but other than some on-air discussions that briefly mention an RF deck design for the higher bands, or maybe a bit of a post here and there, I really haven't seen any major topics about it, or schematics either. I do remember hearing about some device that showed potential on 20 and 15 meters, I though I wrote the number down but can't find it, something sticks in my mind it was an APT fet of some type, I forget the full part number. I would think someone out there would have a functioning transmitter on the air, I've just never seen one yet.
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KD6VXI
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« Reply #1 on: March 30, 2016, 09:58:16 PM »

Here's mine.   125 watts of carrier.   500 peak.   10 meter.

I modulate it with  a Homebrew pwm I've posted before.

I'm so happy ten meters is now dead lol.

The transistor is missing,  due to it being repurchased for 40 meters.

--Shane
KD6VXI


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W3GMS
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« Reply #2 on: March 31, 2016, 01:56:50 PM »

Here's mine.   125 watts of carrier.   500 peak.   10 meter.

I modulate it with  a Homebrew pwm I've posted before.

I'm so happy ten meters is now dead lol.

The transistor is missing,  due to it being repurchased for 40 meters.

--Shane
KD6VXI

Good work Shane! 

What kind of efficiency are you getting on 10M and how are you driving it? 

Joe-GMS 
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steve_qix
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« Reply #3 on: March 31, 2016, 08:08:15 PM »

It can and has been done.  You just have to use more expensive RF MOSFETs, and pay a lot more attention to the layout.
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kb3ouk
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« Reply #4 on: March 31, 2016, 08:18:57 PM »

Here's mine.   125 watts of carrier.   500 peak.   10 meter.

I modulate it with  a Homebrew pwm I've posted before.

I'm so happy ten meters is now dead lol.

The transistor is missing,  due to it being repurchased for 40 meters.

--Shane
KD6VXI

What device were you using?
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KD6VXI
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« Reply #5 on: April 01, 2016, 01:33:06 PM »

Sorry about the delay.

ARF448 in my 500 Watt pep amp.   I've also used an irf640 at ten meters.   100 watts pep,  iirc.

My efficiency is in the 85 to 90 pct area.   Amp is based on an 11 meter ism writeup,  so I'm sure it could use a bit of optimizing.   But,  it was a proof of concept.

I actually have two more transistors.   With a pair,  push pull single ended,  I could have a 250 Watt class amp.

75 and 40 meters has been more on my mind,  lately,  since they are actually active right now.

--Shane
KD6VXI
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KD6VXI
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« Reply #6 on: April 01, 2016, 01:36:09 PM »

GMS:  Drive is complete sinewave drive.   Used a modified Cb radio,  killed the 15 mhz tripler input to the pll.   Ran the mfj259 into the tripler input,  Mfj becomes a nice vfo for complete ten and twelve meter coverage.

That might explain my lower than  expected efficiency as well....   Not that I'm complaining,  but would be nice to be in the mid to upper 90s.

--Shane
KD6VXI
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W3GMS
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« Reply #7 on: April 01, 2016, 08:00:17 PM »

GMS:  Drive is complete sinewave drive.   Used a modified Cb radio,  killed the 15 mhz tripler input to the pll.   Ran the mfj259 into the tripler input,  Mfj becomes a nice vfo for complete ten and twelve meter coverage.

That might explain my lower than  expected efficiency as well....   Not that I'm complaining,  but would be nice to be in the mid to upper 90s.

--Shane
KD6VXI

Yep, I am sure square wave drive would really help with the transition times, hence better efficiency.

Joe-W3GMS
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VE3ELQ
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« Reply #8 on: October 30, 2016, 06:20:59 PM »

The DRF1300 looks interesting for the higher bands up to 10 meters.
Specs here:   http://download.siliconexpert.com/pdfs/2010/9/8/7/1/16/727/mcs_/manual/drf1300_e.pdf

73s  Nigel
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ka1tdq
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« Reply #9 on: October 30, 2016, 10:35:05 PM »

Those look awesome!  The drivers and FETs all in one package.  At $230 each though from DigiKey, they're an expensive experimentation toy.  Probably even after you got it to work, you'd probably just whisper into the microphone to go easy on it. 

"Psssst. How does my 10 meter class E rig sound?  I play it safe and keep the modulation around 15%."

I guess that would level the playing field with high frequency class E running PW modulation as well.

Jon
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