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Finally - Some 4-1000A Grounded Grid Linear IMD Specs




 
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Author Topic: Finally - Some 4-1000A Grounded Grid Linear IMD Specs  (Read 28706 times)
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KM1H
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« Reply #50 on: December 19, 2012, 09:08:52 PM »

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The next project is building a tube amp to go from 10mW to 100 W at -45db 3rd or better, to drive the 8877

4CX350FJ?  Kinda scarce

I dont know what you can drag out of a 8072/8121/8122 at a real low B+. The old Signal One ran a 8072 at around 700V if I remember.
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #51 on: December 19, 2012, 10:56:35 PM »

Shane:  I have tried the notch idea, but the blower noise is too wideband white noise and it takes too much audio with it.   Today I picked up the lumber and insulation needed to make three 4'X8' moveable walls that will seal the noise out, I hope.   Nothing like a QRO, quiet shack.

Carl:  I wouldn't mind trying a lineup similar to that. I need 30db of gain, 10mW > 100w.


I'm taking a different approach down the hill:


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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
ke7trp
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« Reply #52 on: December 19, 2012, 11:07:13 PM »

Tom how about one of the preselectors that follow the radio around via the tuner cable?  That would clean up the tranciever.   They give you 70 DB!..

http://www.arraysolutions.com/Hamation/bandpassfilters.htm


C
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #53 on: December 19, 2012, 11:47:36 PM »

Tom how about one of the preselectors that follow the radio around via the tuner cable?  That would clean up the tranciever.   They give you 70 DB!..

http://www.arraysolutions.com/Hamation/bandpassfilters.htm


C

Hi Clark,

Thanks for the suggestion.  That looks like a nice bandpass filter system - something I'd like for my HPSDR radio.

It would be nice if it were that easy, but in this case we are talking about two different things.  That filter would help the harmonic suppression far removed from the operating freq.  (X2, X3, etc)  Notice the filter is still flat at 15 mhz on 20M.

We need better IMD numbers - from distortion that is generated CLOSE to the operating frequency by a non-linear amplifier. (splatter)    No amount of 2nd harmonic suppression will help that, I'm afraid.  The FT-1000D is what it is and that's about -31db third order IMD at 200w output.  We need something that will do 15db better for close-in cleanliness to do justice to the nice 8877 amplifier IMD numbers.


T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
KB2WIG
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« Reply #54 on: December 19, 2012, 11:51:09 PM »

T,

The old ways are the best.

klc


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What? Me worry?
KM1H
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« Reply #55 on: December 20, 2012, 10:28:32 AM »

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Carl:  I wouldn't mind trying a lineup similar to that. I need 30db of gain, 10mW > 100w

I use a Class A 2N5109 to boost the 10mw from a TS-830 transverter port to 100 mw or so to drive a HA-6 transverter to the 15W needed to drive the 1200W amp. Needed a slip on heat sink due to the bias needed for that mode at 12V.
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