Saturday, November 17, 2012

40m Carolina Windom

There are two versions of the CAROLINA WINDOM® 40 Compact™ Attic Antenna. Each utilizes all of the main features of the CAROLINA WINDOM® 40 Compact™. Beyond that, the antennas are optimized for installations that are close to the ground, like attic and similar installations. The difference in the two models is only in the length of the Vertical Radiator and the bands covered. All of the major HF bands are covered by both models. However, the CAROLINA WINDOM® 40 AV6 Compact™ has a slightly higher SWR on 30 meters, but can still be tuned with a manual tuner or a wide range automatic tuner. If, for some reason, the automatic tuner in your transceiver cannot tune the CAROLINA WINDOM® 40 AV Compact™, an automatic tuner range extender (MFJ-914) can be used.
CAROLINA WINDOM® 40 AV9 Compact™9 foot Vertical Radiator
CAROLINA WINDOM® 40 AV6 Compact™6 foot Vertical Radiator
The Vertical Radiator may be supported by the attic's rafters to gain the extra length needed. The antenna's radiation pattern will be skewed slightly, but there are many other factors which will affect the radiation pattern of an attic installation, so this is not a major issue.


  • Freq. coverage: 40 - 6 meters**
  • Radiator length: Horiz. = 34'
  • Foldback element approximately 8.5'/8' drop
  • Polarization: Both vertical and horizontal components
  • Feed line: 50 ohm Coaxial cable
  • Tuner needed: Yes
  • Power Rating: >1000 Watts but this level is not recommended. For maximum safety, keep the power output of the transceiver at 200 watts or less.***
  • Radials? Not required
  • Most ham bands covered including the WARC bands and 6 meters.
  • It is an excellent receiving antenna.
  • Installation is easy. It's far less trouble than putting a lot of separate antennas in your attic.
  • Special Matching Transformer
  • High efficiency - no ground losses
  • Ground independent - radials not needed
  • The Vertical Radiator provides important vertically polarized components to the radiation pattern which improves signals on the higher bands.
  • The new Matching Unit enhances vertical radiation
  • Automatic tuners in most current rigs will tune this antenna.
* Based on user reports, field evaluations, and product reviews. Gain is due primarily to the low angle radiation pattern.
** The CAROLINA WINDOM® 40 AV6 Compact™ may require a manual tuner or wide range automatic tuner to cover 30 meters. An MFJ-914 automatic tuner range extender will extend the tuning range of your automatic tuner by a factor of about 10.
*** While the antenna is capable of handling more than the recommended 200 watts output on SSB or CW, the close proximity to people and electrical devices inside your house may result in excessive RF radiation levels. Interference with other electronic devices is possible when an antenna is in such close proximity. 
6 m: Limit the power to 100 watts and limit the use to CW/SSB duty-cycles.
Depending on the installation, this antenna may be able to handle AM, FM, RTTY and other high duty-cycle modes if the output power from the transmitter is kept below 100 watts. Under no circumstances, should you exceed 100 watts in these modes when utilizing the antenna inside your dwelling. Also, monitor your reflected power. It it drifts, reduce power.

An antenna support at a height of 15 feet above ground is not going to perform nearly as well as the same antenna supported at 50 feet. Fortunately, the Vertical Radiator in the CAROLINA WINDOM® 40 AV9 or AV6 Compact, will provide better performance than a simple dipole at the same height, but the low support height will reduce the effectiveness of any antenna. However, that doesn't mean that an attic antenna isn't effective. There is a member of a local DX club who uses only attic antennas and has worked hundreds of DX countries (entities). He does live in a two story house, so his antennas are between 25 and 30 feet in the air. Still, it's quite an accomplishment.
I will say that during the testing phase of the CAROLINA WINDOM® 40 AV Compact™, I was pleasantly surprised at how well it actually performed. Most of my testing was done at 20 feet above ground. My reference antennas are supported much higher, but there were times when there was little noticeable difference. The signal strength of incoming signals and signal reports received were only down an S-unit or so from the standard antennas. On other occasions, the difference was larger, as you would expect. The bottom line is this: The CAROLINA WINDOM® 40 AV Compact™ provides a way to put out an acceptable and certainly effective signal on most, if not all, important HF bands. The actual results will depend on your installation, circumstances, and the actual location and height of the antenna installation. Some attics are loaded with metal ducts and wiring. This does not lend itself well to good antenna performance. In some cases an attic installation may not be practical due to metal faced insulation, duct work, wiring and many other things that will interfere with an antenna operation.
Initial feedback from customers installing the CAROLINA WINDOM® 40 AV Compact™ in their attics report better than expected results. Certainly, installing a CAROLINA WINDOM® 40 AV Compact™ is going to give you better results than not having an antenna at all. The multiband coverage and coax feed are all pluses of this antenna system. Still, it can't defy the laws of physics. On the other hand, it just might be your ticket to years of continued enjoyment of Amateur Radio.
Outside Installation
The CAROLINA WINDOM® 40 AV Compact™ is fully weatherproofed (you have to install some Coax Seal which is provided to complete weatherproofing). The antenna could be installed on top of a roof and held in place with roofing cement or other appropriate product. It can be painted to camouflage the installation. It can even be installed as a normal antenna between two supports. If you have that option, support the antenna as high as possible.
With an attic installation, keep the power down. Insulate the wire from wood rafters, floors, etc. The wire is insulated, but you want to insure that the safety factor is high. Don't just nail the wire to the wooden structure. Just use good installation practices, keep safety foremost, use the proper antenna geometry and you'll enjoy many years of service from the antenna. 
VERT™ (Vertically Enhanced Radiation Technique)
The CAROLINA WINDOM® was the first antenna to take advantage of 'VERT™' (Vertically Enhanced Radiation Technique), and this feature continues with the CAROLINA WINDOM® Compact™.
VERT™ (Vertically Enhanced Radiation Technique) is a radiating feed line technique that produces a controlled, low angle vertical radiation pattern. The effect is absent from most ordinary antennas. Field tests, user reports and seven product reviews confirm that the CAROLINA WINDOM® will give you a remarkable performance advantage. The off-center fed CAROLINA WINDOM® provides unusually good performance on all bands covered, including the WARC bands. It's an ideal antenna for those of you who do not wish to use a tower and beam. The CAROLINA WINDOM® is also ideal for those who want a high performance antenna to cover the bands not covered by your beam antenna.

The Secret

It's the Vertical Radiator. Combined with the Dedicated Matching Unit and special Line Isolator, it is responsible for the improvement in the low-angle, vertical radiation pattern.

NRAI Snug Fit Insulator 
Nail-on Rafter Insulator for wood holds antenna wire about 3/4" from surface. Use with rope or insulated wire* up to 5/16". At least 10 insulators are recommended for rafter installations.Requires two (2) #8x3/4" screws supplied by the user.
 SRAI Standoff Insulator
Screw-in Rafter Insulator for wood holds wire about 6" from surface. Recommended for a deluxe installation. Use with rope or insulated wire* up to 5/16". At least 10 insulators are recommended for rafter installations.
Go to the antenna insulators page
*Use insulated wire in attic installations.

No comments: