The New Carolina Windom
By Len Carlson,
Copyright K4IWL, Len Carlson;
condensed from QRP EXPRESSIONS
Newsletter August 5, 2005
with Len's kind Permission
new information 01-07-09)
"The copyright for the
term 'Carolina Windom', as relates to the designs of Jim Wilkie
(WY4R), Edgar Lambert (WA4LVB), and Joe Wright (W4UEB), is owned by
Jim Thompson, (W4THU). All commercial use of the
term the term 'Carolina Windom' and commercial distribution of
'Carolina Windom' antennas is
all ham stations QRO or QRP, ten percent of a stationís success in quality QSOs is the equipment
and the operator. Ninety percent is
the antenna. This is especially true
in QRP since with very low power, by
comparison to the Power Mongers, we need to get more ERP per watt out into the ether to be
So when I
got back into QRP a few years ago I found the fascinating world of antennas and RF radiators
to be an exciting challenge and a
means to find the
perfect antenna which I call the....
have room for an 80-meter dipole or long wire so I have to restrict the length to 100 feet or
less. Besides my primary interests
are working only CW on 40, 30, 20,
and 15 meters.
Based upon these
parameters, I have found what I consider to be the
perfect antenna. The antenna I will show you
how to build in this article evolved from a concept that had its beginning back in
1929 when Loren G.
Windom described his invention in the
September issue of QST, 1929, pages
19-22. Just do a search on Google for more on the "Windom".
A few years ago, three hams, Jim Wilkie (WY4R), Edgar
Lambert (WA4LVB), and Joe Wright (W4UEB), came up with an idea
for an off-center fed dipole that carried Windomís single feed line
antenna to the next level. It has since become known as the Carolina
Windom. I will call this the Traditional Carolina Windom since it
was the first attempt at creating this specific type of multi-band
antenna based loosely on Windomís original concept. The differences
between the New Carolina Windom antenna and Windomís original
is that the Original Windom is not a
Enter the New Carolina
It will operate on 80, 30, and 17
meters but will require a tuner for these bands.
Windom shown cut for 40, 20, 15 and 10
recent, New Carolina Windom, version has some very interesting characteristics
as seen in the drawing above.
For one, the 4:1 Balun has been moved to the antenna radiator and is built into the center insulator.
The other interesting feature is that
the 10 feet of coax from the Balun is
terminated in a choke or line isolator. I have fitted the 10 foot stub with PL-259 UHF connectors
on each end. This allows the coax
vertical radiator to be easily removed if desired. It is designed
vertically which is one reason why this antenna is so
effective. The radiation pattern
the vertical radiator combines both horizontal and vertical radiation components and lowers the effective angle of radiation getting
more of your signal near the horizon.
antenna is in use the world over by DX'ers and DX'peditions. In one Navassa DX'pedition, of the
33,000 QSOs made, more than 27,000
were accomplished with this antenna.
The DX'pedition team also had a beam and
verticals, but the New Carolina Windom
was the antenna they used. Its
reputation for excellent performance is so
good that it served as one of the antennas
in setting two 40 meter "mile-per-watt" world records of nearly 4,000,000 miles-per watt.
The antenna can be used without the vertical radiator
but the radiation pattern will lose the low angle component and may
make the antenna less effective. If the vertical radiator is removed
then you should move the line isolator to the bottom of the
NOTE: This antenna should not need a tuner on the 40, 20,
15, and 10 meter bands although you may use one if you feel the need
to. It will operate on 80, 30, and 17 meters but will require a
tuner for these bands.
Here is the math for designing the New Carolina Windom
cut for your lowest band operation:
Holding true to
the original Windom formulas, we use a ratio of 37.8% for one side
and a ratio of 62.2% for the longest side after determining the half
wave length at the lowest operating
Using 7.1mhz as lowest frequency of
operation we use:
468 / 7.1mhz =
65.9 feet (round to 66 feet) for total half wave length.
side length = .378 (37.8%) X 66 = 24.9 feet = 25 feet
Long side length = .622 (62.2%) X 66 = 41.05 feet =
41 feet rounded
So we have the short length
of 25 feet, and
long side of 41 feet using the
Vertical length for RG58 from balun to choke = 4 to
1 ratio (meter band / 4)
40 meters / 4 = 10
Using 3.9mhz (80/75 Meters)
468 / 3.9mhz = 120 feet for total half wave length.
side length = .378 (37.8%) X 120 = 45.36 feet
length = .622 (62.2%) X 120 = 74.64 feet
Vertical length 4 to 1
radio = 80 / 4 = 20 feet
Editors note: The New
Windom can be designed for 160, 80/75, or any fundamental frequency
you desire as the lowest band of operation and it should perform
better on that fundamental frequency and still resonates on the harmonically related bands
without a tuner. Just keep the original ratios (37.8% and
62.2%) the same by using the formula.
You will have to adjust
the balun to choke length of RG58 in the same ratio by doubling the
length from 10 feet at 40 meters to 20 feet at 80 meters and 40 feet
at 160 meters. The ratio is meters / 4 = length of vertical
If you are a
perfectionist, then you may want to trim ends for best SWR.
According to all who have build the New Windom using these formulas,
they work great! Get is up as high as possible and have
For the complete article and plans for a
homebrew balun and choke,
check out Len's full article here at the Dallas ARC web site! Or....commercial units can be
Updates courtesy of 2E0JCA via email from Len, K4IWL 01-09 (Refer to
full article here)
"On the balanced side of the 4:1
balun, I.e., the aerial side, it makes no difference which side
A note about the choke [between
the balun and the feedline]: The choke [line-isolator] is simply a
straight piece of coax with ferrite cores strung on it. Just use the
same coax that you are using for the field line from the Xceiver to
the choke. I have made a mod to the choke also. Instead of bending
it back inside of the CPVC tube, make it a straight piece of coax
about 0.3 meter. The length is not critical but should be no shorter
than about 12 inches. Use as many ferrite tubes that will fit
in-line on that length.
By the way, not sure if you have
the latest updates to the article. I am enclosing what I have
been sending to all who have requested interest and/or are building
the antenna from "scratch".
The antenna is designed for
QRP. About 25-watts or less
on CW. The antenna itself can
handle 1KW or more power but the balun cannot. Hence the following
Notes on balun updates: (01-09)
If you are building the 4:1 balun
per the article here is a
The core should be a T106-2 (red) core [for QRP].
The wire should be the larger
AWG 20 enameled copper wire (not AWG 26 like in the article).
The minus-2 (red) is the MIX. This IRON CORE TOROID
value MUST BE USED
for the Balun to work and be broadbanded for 4MHz-29MHz.
Wind 26 bifilar turns. This should work to about 25-30 WATTS. For higher power to
about 150W use a T250-2 (red) core and the larger diameter AWG 16 enameled
copper wire. Should be around 30 bifilar
turns."Questions? Email Len at firstname.lastname@example.org
"The copyright for the term
'Carolina Windom', as relates to the designs of Jim Wilkie (WY4R),
Edgar Lambert (WA4LVB), and Joe Wright (W4UEB), is owned by Jim
Thompson, (W4THU). All commercial use of the term the term
'Carolina Windom' and commercial distribution of 'Carolina Windom'
antennas is reserved." CAROLINA
WINDOM AT RADIOWAVZ
POWERED BY HAM