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Technical Puzzle #20 - Fried Doughnuts
Technical Puzzle #20 - Fried Doughnuts
m0jha
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Joined: Sat Jul 21, 2007 9:37 am Posts: 10570 Location: Manchester IO83TK
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Re: Technical Puzzle #20 - Fried Doughnuts
m0jha wrote: will it stay the same??
like 2 people up seperate ladders , 1 stood on the first rung and the other stood on the 3rd rung and asking them both to move up a rung.. the difference in rungs between them is still the same.
billy sorry i quoted myself instead of editing..
_________________ Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.
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Sun Jan 17, 2010 6:00 pm |
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Technical Puzzle #20 - Fried Doughnuts
G3TXQ
Silent Key
Joined: Fri May 22, 2009 1:23 pm Posts: 5637 Location: Northampton IO92ME
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Re: Technical Puzzle #20 - Fried Doughnuts
Billy,
You're correct - the flux stays the same. We could have an open-circuit load on the secondary, or one which drew a large current, the flux would be the same as long as the output voltage didn't change.
Michael Faraday first discovered the relationship between flux and induced voltage: Induced voltage = No of turns x rate of change of flux
No mention of current at all!!
In a transformer - and that includes UnUns and voltage baluns - if you find the core is under thermal stress when handling a particular voltage, you should increase the number of turns. Faraday's equation tells us that must result in a corresponding reduction in the rate of change of flux; so assuming the frequency stays the same, the flux level must decrease.
73, Steve G3TXQ
_________________ "I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;" (Lord Kelvin 1883)
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Sun Jan 17, 2010 6:47 pm |
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Technical Puzzle #20 - Fried Doughnuts
m0jha
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Joined: Sat Jul 21, 2007 9:37 am Posts: 10570 Location: Manchester IO83TK
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Re: Technical Puzzle #20 - Fried Doughnuts
i frighten myself sometimes
_________________ Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.
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Sun Jan 17, 2010 7:35 pm |
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Technical Puzzle #20 - Fried Doughnuts
m0jha
Advanced Member
Joined: Sat Jul 21, 2007 9:37 am Posts: 10570 Location: Manchester IO83TK
Feedback: 60 (100%)
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Re: Technical Puzzle #20 - Fried Doughnuts
m0jha wrote: i frighten myself sometimes im that good
_________________ Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.
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Sun Jan 17, 2010 7:36 pm |
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Technical Puzzle #20 - Fried Doughnuts
G3TXQ
Silent Key
Joined: Fri May 22, 2009 1:23 pm Posts: 5637 Location: Northampton IO92ME
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Re: Technical Puzzle #20 - Fried Doughnuts
Rob, Yes the UnUn should be OK with "sensible" antenna lengths. But if you scour the ads you'll find at least one company that uses a 9:1 UnUn with a 20ft vertical on 80m Steve G3TXQ
_________________ "I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;" (Lord Kelvin 1883)
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Mon Jan 18, 2010 12:11 pm |
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Technical Puzzle #20 - Fried Doughnuts
G7DIE
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Joined: Mon Jan 04, 2010 8:23 pm Posts: 4236 Location: Still by the sea, but sadly only IO83ls
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Re: Technical Puzzle #20 - Fried Doughnuts
G3TXQ wrote: Rob, Yes the UnUn should be OK with "sensible" antenna lengths. But if you scour the ads you'll find at least one company that uses a 9:1 UnUn with a 20ft vertical on 80m Steve G3TXQ I've seen this antenna and wondered just how badly it would perform at lower frequencies, now I know
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Mon Jan 25, 2010 10:10 pm |
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