Alfred E. Newman wrote:

John Doty's noise reducing antenna ideas from his 1993 posting are virtually
identical to noise reducimg antenna ideas found in articles by Denzil
Wraight and me which were published in DX News in 1991.

Decoupling a feedline is decoupling a feedline....

Denzil's article
was titled "Interference Reducing Antennas For The BCB," and mine was
"Inverted L Noise Reducing MF/VLF Antenna."

Is that an oximoron? Seriously...Using an omnidirectional antenna to
reduce *noise* on those bands is kinda counterproductive seems to me...

Denzil and I used twinlead
rather than coax. However, Mark Connelly published descriptions of similar
noise reducinmg antennas using coax in DX News later in 1991. These
articles are available from The National Radio Club http://www.nrcdxas.org/
as reprint A69. Contrary to what John claims, these kinds of noise reducing
antennas are not very effective against noise at SW frequencies much above 6
MHz.

Uhh...Decoupling a feedline is decoupling a feedline. No matter what
frequency...
You can do it at 440 mhz just fine... All my antennas are well
decoupled, and that includes from MW to 440 mhz.


These types of noise reducing antennas were invented by F. R. W.
Strafford in or about 1936, and he discusses these and other types of noise
reducing antennas for short waves in "Screened Aerials," Wireless World,
November 25, 1937, pages 516 - 518.

Decoupling the feedline has been around for quite a while...
I guess I have one issue though, and yes, I am anal retentive...I object
to *any* antenna being called a "low noise" antenna. Why? Cuz they don't
exist. These is no such thing. They should describe all of these types
of decoupled antenna schemes as "examples of better decoupled antenna
*systems*. The lower noise has nothing to do with the antenna itself.
Only the decoupling of the line, coax or ladder line. And to top this
off, if you are in a quiet area with no noise to pickup, using the
decoupling schemes will not do *anything* at all to reduce noise. The
performance will be exactly the same. IE: out in the woods, running
battery power, etc...A *true* noise reducing *antenna* would work
anywhere, but again, as far as I'm concerned, they don't exist. The on;y
way to really reduce noise using the antenna itself, would be to change
polarity. That would reduce an opposite polarized signal about 20 db or
so...
As far as the decoupling losing effectiveness over a certain freq, thats
a design issue with the decoupling scheme being used. Balun, chokes,
etc...BTW...I include the so called "shielded loops" with the "misnamed"
antenna group. In all tests I've ever run, I've never seen any
indication a shielded loop is any *quieter* to noise pickup than a
regular open loop. But the reason there is not due to decoupling of the
feedline per say, although a lack of decoupling can effect the overall
balance. It's due to the shielded loop providing inherent good balance
due to it's design. But if you have an open loop just as well balanced,
it will null noise sources just as well as a shielded loop. A shielded
loop is not any quieter to far field noise, than any other loop if you
are not using it to null the noise source. It *could* do a better job of
nulling that source, *if* the balance on the open loop was poorer, but
again, this is a design issue..You can design the open loop to be just
as balanced. MK

--
http://web.wt.net/~nm5k