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Author Topic: What is the best SW antenna ?  (Read 42876 times)
W0BTU
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« Reply #45 on: September 03, 2012, 04:04:23 PM »

Notice that I used the term "shielded".

Yes, I noticed that. :-)

Please notice that W8JI states (at the first link) that "Folklore claims a small 'shielded' loop antenna behaves like an electrical sieve of sorts, sorting 'good magnetic signals' from 'bad electrical noise'. Nothing is further from the truth! At relatively small distances a small magnetic loop is more sensitive to electric fields than a small electric field probe."

Believe me, Tom knows exactly what he's talking about! I built such shielded loops from 1/2" hardline  some years ago.

Respectfully,
Mike
« Last Edit: September 03, 2012, 04:12:40 PM by W0BTU » Logged

KB5UBI
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« Reply #46 on: September 03, 2012, 04:31:07 PM »

I too, respect W8JI's opinions. Tom has vast knowledge and practical experience in the field. Don't take everything he, I or others say out of context.

I was first exposed to Shielded Loops in the late 60's when working on an Electronic Counter Measures project and developed my opinion then, but we can agree to disagree. It's an opinion, a theory and nothing more. My opinion: An unsheilded loop will pick up electromagetic (radio waves) and electrostatically induced noise (most man made noise). Most man made noise, has little chance being transformed into true EM radiation. A shielded loop, is mostly insensitive to electrostatically induced noise and when balanced, also has very sharp nulls giving us two chances to rid ourselves of locally generated noise. 

KB5UBI
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W0BTU
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« Reply #47 on: September 03, 2012, 04:34:47 PM »

Maybe I am taking some of this out of context. I guess it depends on how close the RFI source is. :-)

Exactly what do you mean by "electrostatically induced noise"? A corona discharge is all I can think of that fits that description.
« Last Edit: September 03, 2012, 04:40:55 PM by W0BTU » Logged

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