THE CAROLINA WINDOM
This page is dedicated to Martin, a friend of mine. He wants an all-band... Correction, an all-frequency aerial, fed with coax. I must admit that I knew nothing about the Carolina Windom. However, with Martin in mind, I've done a little research into this aerial.
In the Carolina Windom, the current in each of the wire radiator sections is out of balance. Why? Because the two wires either side of the feed point are of unequal length. (Unlike a centre-fed dipole) Coaxial cable (which is not a balanced line) will radiate when the voltage and phase relationships are not properly balanced. OK? Got that?
Here's en excerpt from an advert... The 'Dedicated Matching Unit' is used to match the transmission line (coax feed line) to the antenna is a special design that enhances transmission line radiation.
Dedicated Matching Unit? Special design? What a load of crud! The Dedicated Matching Unit of special design is nothing more than a 4:1 bloody balun. OK, enough of my gripes.
Part of the coaxial feed-line serves not only as the transmission line but, simultaneously, as a vertical radiator. The wire portion of the antenna is the counterpoise for the vertical radiator. The result is an inverted-vertical antenna located high in the air and free of ground losses. The combination of horizontal high angle radiation and vertical low angle radiation accounts for the alleged excellent performance of the Carolina Windom.
Here's another excerpt from an advert... The Line Isolator effectively separates the transmission line portion of the cable from the radiating portion. Vertical radiator length is predictable and repeatable. A Line Isolator is placed in series with the transmission line at a critical point. The Line Isolator provides a large inductive reactance at the insertion point (the action is similar to an RF choke). This effectively eliminates transmission line radiation beyond the point where it is inserted into the transmission line.
Line Isolator? Another load of crud. The LIne Isolator is nothing more than a ferrite ring or sleeve! Whatever you do, don't buy an aerial. I find it incredible to think that people go out and buy a simple G5RV aerial. Two lengths of wire, some coax and a length of ribbon feeder... There's nothing to the damned thing!
Below is a diagram of the Caroline Windom. Measurements are in feet, the insulators speak for themselves and the vertical radiator is 50 ohm coax. It's as simple as that.
The diagram below shows the 4:1 balun. The number of turns depends on the thickness of the wire and the size of the ferrite ring. Around 18 turns is a good starting point. You can always add or remove turns if things don’t look too good.