[HCRA] Antenna Design

Fri Jun 11 20:43:30 EDT 2004

Key phrase from ARRL's Dean Straw, N6BV, who is our (ie, ARRL's) antenna
expert:

"But I remain somewhat skeptical,'' he said. "I'd like to see some
validated field test measurements."

Anecdotal evidence is great but as Dean likes to say "RF gotta go some
place," and "You can't defy the laws of physics."

That said, claims that a smaller antenna is going to be from 80% to 100%
efficient (as Mr Vincent--he's not a degreed engineer--asserts) tend to
stretch credulity. There's no mention of the tradeoff in bandwidth with
smaller antennas either.

Several of our members spotted this article (our PR folks arranged for
Dean to speak with the NYT reporter) as well as one that's on the
University of Rhode Island Web site.

Definitive tests of this antenna at an antenna testing range would
determine where the facts lie. Remember the article in QST a while back
about how much you could work by feeding RF into a light bulb
(essentially a dummy load) on a pole? This reminds me of the so-called
"crossed field array" or CFA antenna debate. The efficacy of those short
antennas also has been supported so far only by anecdotal evidence.

It's no big feat to work a lot of DX with a minuscule antenna. I've
worked well over 100 countries from my mobile, many of them on 40 meters
where the antenna is essentially a center and top-loaded monopole that's
fractionally smaller than a halfwave dipole--about 1/9th the size, in
fact. Last evening--you HF ops know how poor the bands have been--I had
a ragchew with a station in France on my way home from work--the sun had
not yet set--on 40 meter CW.

I've also had successful contacts loading up a 10-15 foot piece of wire
lying on the floor of my basement (I was testing a tuner I'd just built
at the time).

Then there's the guy in Virginia (W9JOP) who got WAS running 250 mW
(crystal-controlled, no less) on 40 and 20. See the story in this week's
edition of The ARRL Letter or on the ARRL Web site.

I'd like to believe this guy's onto something, but, like Dean, I remain
skeptical.

73, Rick, N1RL 
(ARRL Senior News Editor)

-----Original Message-----
From: hcra-bounces at mailman.qth.net [mailto:hcra-bounces at mailman.qth.net]
On Behalf Of Larry Krainson
Sent: Friday, June 11, 2004 8:29 AM
To: HCRA Email List
Subject: [HCRA] Antenna Design

______________________________________________
-------Hampden County Radio Association-------
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A friend sent me this article from the NY Times.

Enjoy,

de WB1DBY

>
> Intriguing the Physicists, Radio Buff Shrinks an Antenna
>
> June 10, 2004
>  By IAN AUSTEN
>
>
>
>
>
> WHILE a lifetime in ham radio played a role, it was love
> that ultimately led Rob Vincent to develop what he says is
> a way to make antennas significantly smaller but still efficient.
>
> "About 1995 I had met a sweetheart and we fell in love,"
> Mr. Vincent, now 60, recalled. "I went to live with her,
> but the only problem was that she lived on this postage
> stamp of a yard in a congested neighborhood."
>
> The real estate owned by Carolyn Hardie, the woman Mr.
> Vincent later married, was an issue because his amateur
> radio interests had turned toward frequencies in the
> 160-meter band. That band is close to broadcast AM radio.
> And, like an AM station, operating on it requires a tall antenna - in
> Mr. Vincent's case, one that is 140 feet high. Aesthetic and zoning
> questions aside, the 50-by-100 foot lot was not big enough to
> accommodate the guy wires needed to stabilize a tower that high.
>
> So Mr. Vincent, a technician with the University of Rhode Island's
> physics department, began thinking about ways to make antennas
smaller.
> The end result is a system that he claims can produce antennas that
are
> one-third to one-ninth as high as normally required. He has spoken to
> other ham operators in over 80 countries on the 160-meter band through
> his relatively new, self-supported backyard tower, which is one-third
of
> the conventional minimum size.
>
> Mr. Vincent said his improvements were not just applicable
> to ham radio towers. They could be used to either further shrink the
> tiny antennas in cellphones, he said, or boost their efficiency.
>
> Small yet efficient antennas have long been a goal for
> radio researchers, said R. Dean Straw, the senior assistant technical
> editor for the American Radio Relay League, an association of amateur
> operators. "The holy grail is an antenna the size of a grain of salt
> that produces big signals," he said.
>
> Generally the size of antennas increases with the
> wavelength of the frequencies they are transmitting or receiving.
While
> there are several formulas for determining optimum height, the height
of
> most antennas is one-quarter to one-half the wavelength. At 140 feet,
> for instance, Mr. Vincent's ham tower would have been slightly higher
> than one-quarter of the wavelength of 160 meters, which is equal to
525
> feet.
>
> Smaller antennas can be used, but with a trade-off. "When
> you get below a quarter-wavelength, efficiency drops off
dramatically,"
> Mr. Vincent said.
>
> Before arriving at the university in the early 1990's in a
> still-unfulfilled quest to complete his undergraduate degree, Mr.
> Vincent spent about 30 years in radio-related engineering jobs, mostly
> with a radar division of Raytheon. But his tinkering with antennas
dates
> back to when he obtained his first amateur radio license at the age of
> 14.
>
> "I've always had a natural understanding of radio - maybe
> it's from a prior life," Mr. Vincent said. "But in those
> early days I could not fathom how an antenna worked."
>
> The relationship between antenna height and efficiency was
> so well established that he initially kept his antenna-shrinking work
a
> secret. Mr. Vincent also acknowledged that he had relatively little
idea
> of what might work when he began the project.
>
> "When I started out to do this it was 10 percent theory and
> 90 percent black magic," he said. After reviewing much of
> the literature, Mr. Vincent started designing antennas with special
> simulation software on a personal computer.
>
> From the most promising of those virtual designs, he ran
> tests using antennas that were about 18 inches high and fashioned from
> copper-covered Plexiglas rods. One model seemed particularly
successful
> until it lost its signal during a high-powered broadcast test. When
Mr.
> Vincent went outside, he found only a lump of molten metal and
plastic.
>
> Gradually, he said, potential areas of improvement became apparent. He
> began confiding in some friends from the ham radio world and faculty
> members in the physics department. One friend allowed Mr. Vincent to
> build a 46-foot-high experimental antenna at his country home, which
> includes a salt marsh.
>
> Saltwater is an antenna builder's dream. By providing a
> highly conductive base for the antenna, the water improves reception.
>
> The big prototype improved upon conventional designs in
> many ways. But one crucial one involved the placement of devices known
> as load coils along its length. Load coils are commonly used in
> cellphone antennas to alter their current patterns.
>
> Conventional broadcast antennas, Mr. Vincent said,
> generally have a lot of current at the bottom and very
> little if any at the top. With his design, current is more evenly
> distributed.
>
> To avoid suggestions that saltwater, not his design, was
> the magic, another 46-foot prototype followed, built on
> rock. It offered 80 to 100 percent of the efficiency of an antenna
three
> times its size.
>
> About three years ago, the University of Rhode Island
> became interested enough in Mr. Vincent's work that it gave
> him office space. After a review by engineering and physics
professors,
> it began the process of patenting and selling the technology. Mr.
> Vincent has turned over all his rights to the university.
>
> "We've seen test data from Rob Vincent and it sure is attractive,"
said
> Quentin Turtle, the director of industry research and technology
> transfer for the university.
>
> Mr. Straw of the radio relay league said he was impressed
> with Mr. Vincent's work ethic. "But I remain somewhat skeptical,'' he
> said. "I'd like to see some validated field test measurements."
>
> Mr. Vincent said he was aware that would-be buyers of his technology
> would demand better test results, although measuring the efficiency of
> antennas is difficult. But given the scrutiny his project has received
> to date, he said he was confident that his antennas would pass muster.
>
> "I'm part of the technical staff to a whole bunch of
> Ph.D's," he said. "You can't fool these people."
>
>
http://www.nytimes.com/2004/06/10/technology/circuits/10next.html?ex=108
> 7881744&ei=1&en=09fb214d67020e08
>
------Hampden County Radio Association-------
An ARRL Special Services Club for over 50 years
------------http://www.hcra.org------------
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