Wire Antenna Suspension System

Back in October, 2019 I started planning a way to get the Barker & Williamson BWD-90 folded dipole up and running. Well, now it's up and here's how I did it.

Materials

350 feet of good 3/16" cord

Three (3) stainless steel pulleys (only 2 if your tower standoff arm already has pulleys)

Three (3) weights of the same weight (I cut solid metal bars to 5 pounds each)

Tools

A good throw line with launcher

A cutter for the cord

A lighter to melt the cord ends

How To

With a throw line, pull the two pulley cords (the red lines in the drawing) up and over the two support branches. Temporarily, leave the end with the pulley within reach from the ground.

Attach a cord to each end of the dipole antenna. 

Pass the antenna cords through the pulleys, leaving a generous length of cord on each end to accommodate for it's final horizontal length and vertical height. 

Temporarily attach a weight to each of these antenna cord ends.

If you are using a center support cord, attach a cord to an insulated center part of the antenna. Take the other end and run it through the center pulley. Tie a knot so it can't fall out of the pulley.

Pull the pulley cords, lifting the pulleys to full height. Leave about 18 inches of cord between the pulley and the support branch. While lifting the pulleys, the antenna cords should be moving through the pulleys and start raising the antenna.

When the pulleys are up in final position, cut the pulley cords just above ground height. Tie a loop and attach the loop to the base of the tree with a screw eye.

Pull the center antenna cord up to bring the antenna center into final position. Just above ground level, cut the cord and attach a weight. Temporarily secure this line to the tower to maintain the center positioning.

Pull the end cords to bring the antenna ends into final position. Just above ground level, cut the cords and attach the weights. The weights must be free to move, unrestricted, up to the pulleys.

Remove the device temporarily securing the center cord and weight. All three weights should now be just above ground level and free to move up as needed.

From time to time you may need to lower the antenna, so keep a length of cord to attach on the pulley lines for lowering. 

With this system, there is no extra cord laying on the ground to get caught in the lawn mower!

Enjoy your free-floating, suspended wire antenna without worry every time a storm blows!

The BWD-90 Folded Dipole

With all of the projects and ideas racing through my head lately, I realized I have neglected to set up the Barker and Williamson BWD-90 folded dipole antenna I got from my dad, K2JGL (SK). I have been very preoccupied with C4FM, MMDVM devices, repeaters, Raspberry Pi computers, WIRES-X, lightning arrestors, grounding, and maybe a few other things. It's time to get back on the air on HF and make some real DX QSO's with the awesome BWD-90 antenna.

Walking through our property looking for a suitable location to set up the antenna, I see this is going to be a bit more difficult than previously thought. The basic site characteristics to setup the antenna would be a flat open space at least 120' long, 50' wide, and 50 ' high. Well, we live in the woods, so that's not going to happen. Guess I'll have to settle for whatever site I can find.

One of the many great benefits of this antenna is the ability to change takeoff angles. My plan is to have the ability to adjust the antenna for several configurations. The following is taken from the Barker & Williamson user instructions.

NVIS propagation is performed as a flat-top with height varying from ground level to approximately 12 feet. This height is dependent on the ground (soil) conditions. It may be possible to lay the antenna on the ground in desert/low water table environments. The B&W NVIS pole kits allow multiple heights. In NVIS installations a counterpoise will sometimes enhance performance. If you are not getting enough distance from your NVIS setup, try raising the center of the antenna a few feet to make a very shallow inverted Vee. (Appropriate NVIS daytime frequencies are approx 5-12 Mhz, nighttime are 2-4 Mhz.) 

Conventional propagation minimum clear height is recommended at 25 feet for operation down to approx 3.5 Mhz (ends 12 feet for inverted Vee or sloper), and 40 feet for 1.8 Mhz (ends 20 feet for inverted Vee or sloper). Less height does not disqualify operation, but may require a tuner on the lowest frequencies. Also, propagation may be reduced with inadequate height on the lower frequencies. 

The next step is to design a support system that includes a left, center, and right side pulley system so the antenna can be set in any position with the ends from 12' to 24' high, and the center from 12' to 40' high. This would allow everything from a flat-top at 12', to an inverted V at 40' above ground.

See the Wire Antenna Suspension System to see how I finished this project.