The Carolina Windom.The Carolina Windom.A long wire antenna for A long wire antenna for

portable operation.portable operation.

If you want a good argument on HF If you want a good argument on HF antennas bring up the Carolina antennas bring up the Carolina

Windom.Windom.Craig Williams W6CAWCraig Williams W6CAW

GoalsGoals

An effective multi-band, antenna for portable An effective multi-band, antenna for portable and emergency HF operations.and emergency HF operations.

Can work without an antenna tuner.Can work without an antenna tuner. Easy to construct and deploy.Easy to construct and deploy. Can be used for local Near-Vertical Incident Can be used for local Near-Vertical Incident

Skywave (NVIS) or long hall Skywave (NVIS) or long hall communications depending on frequency.communications depending on frequency.

Cheap!Cheap!

But first - What is NVIS?But first - What is NVIS? Near-Vertical Incident SkywaveNear-Vertical Incident Skywave (NVIS) (NVIS)

propagation is generally considered to be F-propagation is generally considered to be F-layer ionospheric reflection at angles of 70-layer ionospheric reflection at angles of 70-90 degrees. It is skywave propagation 90 degrees. It is skywave propagation without the usual skip zone. The purpose of without the usual skip zone. The purpose of NVIS is to communicate locally and NVIS is to communicate locally and regionally, out to a few hundred miles, with regionally, out to a few hundred miles, with moderate power, simple antennas, and no moderate power, simple antennas, and no skip zone. NVIS is typically used on 160, skip zone. NVIS is typically used on 160, 80/75, 60, and 40-meter bands by Amateur 80/75, 60, and 40-meter bands by Amateur radio operators using relatively low radio operators using relatively low horizontal wire dipole antennas. horizontal wire dipole antennas.

From: http://www.athensarc.org/nvis.asp

NVIS or ?NVIS or ?

75-meter NVIS antenna at 20 feet high.The -10db ray is at about 38 degrees.The -20db ray is at about 20 degrees.

75-meter antenna at 125 feet high (half-wave).No longer NVIS, but now a "skip" antenna, with most of the power at about 42 degrees.

From: http://www.athensarc.org/nvis.asp

NVIS and the F-layerNVIS and the F-layer

Above shows two of the three mechanisms that combine to attenuate low-angle daytime signals: (1) Compare the radiated power, which is about 2db below peak at 70 degrees, with the 30 degree angle, which is down about 14db. (2) Compare the distance the rays must travel through the absorptive D-Layer (twice) at various angles: the 30 degree ray has about twice as much loss as a very high angle ray. (3) Add the normal attenuation due to path length (not shown). These three factors, plus a little loss in the troposphere, all combine to attenuate low-angle signals in the daytime. As the sun gets higher, D-layer ionization intensifies, and the effective range decreases further.

From: http://www.athensarc.org/nvis.asp

What is a What is a Carolina Carolina Windom?Windom?

I found this Radio Works I found this Radio Works Windom as I was Windom as I was putting this putting this presentation together. presentation together. $140.00!$140.00! www.radioworks.com/www.radioworks.com/ccwcover.htmlccwcover.html..

Now, lets make one for Now, lets make one for considerably less.considerably less.

The 4 to 1 BalunThe 4 to 1 Balun

How to at: www.w5fc.org/files/how-to/QRP%20Expressions_version_1.pdf

Toroid is a T106-2, Wireman Part # 903

Testing the BalunTesting the Balun

A 200 Ohm resistor is A 200 Ohm resistor is connected between the connected between the balanced leads A1 and B2 balanced leads A1 and B2 to simulate the 200 Ohm to simulate the 200 Ohm feed point of the antenna.feed point of the antenna.

The 50 Ohm test device is The 50 Ohm test device is connected to the connected to the unbalanced feed point.unbalanced feed point.

VSWR should be 1.0 across VSWR should be 1.0 across frequencies of interest. frequencies of interest.

4 to 1 built for light weight4 to 1 built for light weightThe throw away putty knife Balun. The material is easy to work with, cheap, and should hold up well for temporary use. I decided to add terminals for easy of assembly and future repair. The coax is attached on the back side with the shield soldered to the ground windings on the balun and the coax center to B2. B2 and A1 go to the wire. The formula to compute the length of the wire is the standard 468/frequency with the 4/1 Balun at 62.2% from one end.

The wire is Toughcoat 'Silky' 26 AWG, 19 strand 40% copper-clad steel from the Wireman # 534

4 to 1 Balun Potted4 to 1 Balun PottedBalun “potted” with liquid RTV.Balun “potted” with liquid RTV.

Common ModeCommon Mode

On an 80 Meter Carolina On an 80 Meter Carolina Windom the Current Windom the Current Balun is placed around Balun is placed around 22 feet down the 22 feet down the vertical feed line from vertical feed line from the feed point. Using the feed point. Using this 22 feet of common this 22 feet of common mode as a radiating mode as a radiating element the antenna element the antenna pattern is filled in as pattern is filled in as seen here.seen here.

Radiation PatternRadiation Pattern

At the design frequency of At the design frequency of 80M the OCF antenna will 80M the OCF antenna will have a similar pattern to a have a similar pattern to a center fed antenna.center fed antenna.

At higher frequency At higher frequency harmonics the OCF will harmonics the OCF will have gain and pronounced have gain and pronounced lobes towards it’s long lobes towards it’s long end. The pattern in Fig. 4 end. The pattern in Fig. 4 is for a is for a two wavelength two wavelength dipoledipole. Keep this in mind . Keep this in mind when “pointing” your OCF when “pointing” your OCF antennaantenna

From: From: http://www.blacksparrowmedia.com/misc_fileshttp://www.blacksparrowmedia.com/misc_files/The%20OCF-dipole3col.pdf/The%20OCF-dipole3col.pdf

Antenna Current distributionAntenna Current distribution

Current distribution at Current distribution at center, 90 degree, and center, 90 degree, and OCF fed, 60 degree, OCF fed, 60 degree, feed points.feed points.

At 80M the center feed At 80M the center feed point = 70 Ohms. point = 70 Ohms. Above 80M it varies Above 80M it varies between 70 and 3000 between 70 and 3000 Ohms!Ohms!

The OCF feed point is The OCF feed point is around 300 Ohms at around 300 Ohms at 80M through 10M. This 80M through 10M. This is the key to multi-band is the key to multi-band operation with the Off operation with the Off Center Fed (OCF) Center Fed (OCF) antenna. antenna.

From: From: http://www.blacksparrowmedia.com/http://www.blacksparrowmedia.com/misc_files/The%20OCF-misc_files/The%20OCF-dipole3col.pdfdipole3col.pdf

Antenna Length and Balun Placement?Antenna Length and Balun Placement?

Overall length of the wire. Use the standard formula Overall length of the wire. Use the standard formula of 468/ frequency in Mhz for the total length. I find of 468/ frequency in Mhz for the total length. I find this is usually long which is a good thing. In this is usually long which is a good thing. In portable operation I fold back the ends to get a portable operation I fold back the ends to get a better match for the current environment it finds better match for the current environment it finds itself in. ( height, ground Xr, surroundings )itself in. ( height, ground Xr, surroundings )

Balun placement. I have been using the figure of Balun placement. I have been using the figure of 62.2% from one end. On 80M this morning WM6Z 62.2% from one end. On 80M this morning WM6Z from Imperial says he moves his balun around till from Imperial says he moves his balun around till he gets the best VSWR with his analyzer. Why he gets the best VSWR with his analyzer. Why didn’t I think of that?didn’t I think of that?

The Current BalunThe Current Balun

The current balun is made from 7 The current balun is made from 7 clamp on torroids from the clamp on torroids from the Wireman, part # 916. The RG58 Wireman, part # 916. The RG58 feed line is looped through the feed line is looped through the torroids 3 times. My current torroids 3 times. My current balun’s are somewhat a guess balun’s are somewhat a guess from looking at many articles on from looking at many articles on the internet. the internet.

You know they work when your You know they work when your tuner tunes properly. When they tuner tunes properly. When they don't your tuner does a long don't your tuner does a long mad hunt and never seems to mad hunt and never seems to settle in as the common mode settle in as the common mode current is still on the feed line.current is still on the feed line.

The MastThe Mast

33' fiberglass push up 33' fiberglass push up pole from The Mast pole from The Mast Company. Company. www.tmastco.comwww.tmastco.com

The pole is mounted in The pole is mounted in an RV flagpole mount I an RV flagpole mount I got at the Del Mar Fair.got at the Del Mar Fair.

Home Made Mast MountHome Made Mast Mount

A home made version of A home made version of the tire mount. The flat the tire mount. The flat part was laying around part was laying around the barn. It could be the barn. It could be duplicated with duplicated with anything sturdy enough anything sturdy enough not to flex. Attached to not to flex. Attached to the "tire holder" is a the "tire holder" is a hardware store pipe hardware store pipe flange. Screwed into flange. Screwed into the flange is a piece of the flange is a piece of pipe screwed to a pipe screwed to a female plastic PVC female plastic PVC connector. Glued to the connector. Glued to the PVC connector is a PVC connector is a length of PVC pipe to length of PVC pipe to drop the push up pole drop the push up pole into. Adjust your PVC into. Adjust your PVC pipe sizes to pipe sizes to accommodate your accommodate your push up pole diameter.push up pole diameter.

DeployedDeployed

MeasurementsMeasurementsVSWR and more for the finished 80M Carolina WindomVSWR and more for the finished 80M Carolina Windom

( Adjusted for the General phone upper portion of 75M )( Adjusted for the General phone upper portion of 75M )

F MHzF MHz VSWVSW RsRs

3.83.8 1.71.7 7171

3.93.9 1.41.4 4141

7.1757.175 2.42.4 2020

7.37.3 2.52.5 2020

14.3514.35 2.72.7 3131

Measured with an MFJ-269 antenna analyzerMeasured with an MFJ-269 antenna analyzer

160 Meter Windom160 Meter Windom

Measured with an MFJ-269 antenna analyzerMeasured with an MFJ-269 antenna analyzer

Questions ?Questions ?More details on this project, with links to sources, and other projects by W6CAW More details on this project, with links to sources, and other projects by W6CAW

can be found at:can be found at:www.craigwilliams.com/radiowww.craigwilliams.com/radio