Alfred E. Newman wrote:
Hi whatever your name is,

I am puzzled. If, as you wrote, John corrected you on the 'fact' that he
did not "Invent" these Antennas or the Design Concepts of these Low Noise
Antennas, then presumably he told you who did. So why have he and you
neglected to mention that in your writings?

RHF can't tell you because I didn't tell him. I didn't tell him because
I don't know. I know that the principles behind this kind of system were
well understood by radio engineers 70 years ago. I don't know the
original sources.

The idea of using a transmission line to prevent EMI pickup goes back at
least to 1877. According to the February 19, 1881 issue of Scientific
American, the US patent office ruled (in a dispute with Alexander Graham
Bell) that David Brooks had invented the "return wire" as a way to
reduce crosstalk between telegraph and telphone lines (and if someone
were to cite earlier work by, say, Kelvin, I wouldn't be surprised).


It was Denzil Wraight, in fact, who rediscovered Strafford's work on noise
reducing antennas, and who discovered by trial and error reasonable turns
ratios for the antenna matching transformers (Strafford does not discuss
that in his articles). So it is Strafford and Wraight that Doty plagiarized
and you failed to cite.

I've never heard of either of these people. My approach is apparently
more theoretical: if you understand the physics you don't need to
experiment with turns ratios (it's a "back of the envelope"
calculation). My writing is my own, not copied from anyone. The design
itself is a combination of well known ideas that should be obvious to an
expert: that makes it engineering, not invention.

Denzil used a vertical noise reducing antenna,
wrote me about how well it worked, and included a copy of Strafford's
Wireless World article. First I constructed a "top fed" vertical version
with mast almost touching my house. I didn't expect it to do much fow man
made noise in the MW band (my main interest), but to my surprise it did. In
my case, there was little, if any, difference noise reduction between
mounting the vertical mast almost touching my house, or 100 feet away. So
this kind of noise reducing antenna is ideal for DXers with limited space.
Next I implemented an inverted L version of Strafford's noise reducing
antennas. If I recall correctly, the first L was about 100 feet horizontal
and 15 feet vertical. I experimented with both base feed and top feed.
Both gave excellent noise reduction in the MW (and VLF) band(s). Both
Denzil and I used twin feed instead of coax because twin feed tends to pick
up less local nois than coax.

If you're getting less pickup with twin lead than coax, there's
something amiss with the way you're using the coax. In general, coax
picks up much less than twinlead. The EM field of coax is confined
within the cable. The field of twinlead surrounds the cable, making it
much more susceptible to to external coupling.

Denzil and I wrote two separate articles for
DX news (The National Radio Club http://www.nrcdxas.org/ reprint A69) that
were published in the early summer of 1991. I had sent Mark Connelly
preprints of our arfticles, and he developed coax feed versions of
Strafford's noise reducing antennas. According to Mark, the coax feed
variant picked up little, if any additional noise compared to the twin feed
version. At one point in these experiments I tried shielded twin lead, but
found no further noise reduction (or increase).

I got to know Mark a few years after I wrote the article. His approach
is similar to mine, but there are some important differences. He uses
transformers for isolation as well as matching. I shunt the common mode
current to ground at the ground stakes, while absorbing the common mode
energy by burying the coax between them.

Mark never accused me of intellectual theft.


Presently I use top fed inverted L noise reducing antennas as parts of my
phased arrays. Unless you are listening above 16 MHz or so, or have an
insensitive receiver, you don't really need (or want) a big inverted L. Mine
are 15 feet up and 30 feet horizontal. The matching transformer we
used then (and which I still use now) is an Amidon FT-114-75 (the 75
material may have been replaced with J material), 43 turns to 9 turns (at
the center of the 43 turns) #20 enameled copper wire. The twin lead I still
use is Radio Shack speaker wire (#18 stranded, 7 strands of, I think, #26).
It is cheaper ane easier to use than real twin lead, and had about the right
characteristic impedance (about 100 ohms). You'll need a balun (1:1) at
your receiver to convert the balanced lead in to your unbalanced receiver
antenna input (9 bifilar turns of #20 enameled on an FT-114-75 will do).

Like I said before, the noise reducing properties of these kinds of antennas
begin to decline as you go higher in frequency, and above 6 MHz there is not
much noise reduction. If you believe you got substantial noise reduction
above 6 MHz due only to using one of these kinds of antennas, then you are
mistaken. For SW, Strafford recommended doublet antennas for noise
reduction. I do not have much experience with these because I am not much
of a SW listener. What little experience I have suggests that phased arrays
are much more effective at reducing SW noise sources. Unfortunately,there
are no good phasers that you can buy.

I measured 36 dB of EMI reduction at 25 MHz with one of my antennas. If
you're not getting good EMI reduction at SW there's some important
difference between your approach and mine.


As for publishing these articles on the web, that would involve considerable
work. The articles were produced with typewriters, and contain hand
drawings. To convert them to .PDF or other files would be non-trivial, and
would require NRC approval. Anyone who wants these articles can easily
purchase them as reprints from the NRC at the web site above using PayPal or
other methods of payment.

The trouble is that most people who are interested will never even know
what to order. Allowing your work to be freely published on the web is a
good way to get it circulated. Credit for ideas tends to flow to those
whose disseminate them, regardless of precedence or the desires of the
people involved.


Best regards,

Dallas

-jpd