This all started back in June when Gary, W9XT (Unified Microsystems) gave a presentation at the Wisconsin Amateur Radio club meeting about some updates that he recently made to his K9AY antenna . At the time I didn’t have a radio with a separate receive antenna input so while interesting I filed it away as something to build at another time. But that changed in July when I obtained my TS-590SG. Now my gears starting whirring. The planning started in earnest. The first problem to solve was location. Where could I put a K9AY antenna such that it wouldn’t be bothered? While we have enough room it’s still a 30 foot diameter circle of antenna space and I didn’t want it to be disturbed by lawn tractors, ATVs, snowmobiles, dirt bikes, etc. Was there some means by which to create a smaller footprint?
As I was reading the original K9AY article in the September 1997 issue of QST the part that added to the footprint problem for an original\standard implementation were the support ropes that essentially create the loops. These two supports make a 30 foot diameter circle more like 40 feet in reality. That’s moving the footprint in the wrong direction. What if the supports could be moved to the inside of the circle? As I was doodling the shape of the loop, dividing it into the four right triangles that comprise it, and working out the lengths of the legs and the angles the shared leg of the bottom and top triangles emerged. (Sorry, I’m an engineer…I figure if Pythagoras went through the trouble to sort out the math the least we can do is use it whenever possible if for no other reason than to check his work.) What if the shared leg could be a support of some kind? This would certainly help to solve the footprint problem.
The shared leg
This led to some more conceptual drawings ultimately resulting in this design:
And once the supports were on the inside of the circle the next logical improvement was to hinge them in some manner such that they could be moved upward out of the way of any number of wheeled conveyances if needed.
K9AY support arms detail
With this design the diameter of the antenna circle was 30 feet, not more and could be substantially reduced if necessary to a few feet.
With the design in hand the next step was a design review and site choice meeting with my XYL. After some hemming and hawing a suitable location was agreed upon and construction began. Thankfully I have two strong sons, my youngest, Ben, manning the post hole digger to make the hole for the 4×4 post that would form the base of the antenna.
Ben and the base
The base was placed in the hole accompanied by a bag of Quikrete. The next step was to build the arm holders which were constructed from 2×8 treated lumber.
The next step was to bolt in the arm supports, constructed of 2×4 treated lumber.
I considered a few different materials for the support arms including Crappie fishing poles but in the end settled on schedule 40 PVC conduit mostly because it’s readily available and very inexpensive. If it doesn’t work for some reason I’ll update the arms to some other (better?) material.
Support arms attached
I did not want the antenna wire to bear all of the weight of the arms so support ropes were needed. I constructed an attachment plate out of Kydex to fit at the joint of the mast pieces to provide a place to attach the support ropes to the mast.
Arm support rope attachment plate
And likewise another Kydex plate was constructed for the top to provide a place to attach guy ropes and the top supports for the antenna wires.
Given that the support mast is 24 feet tall all of the arm support ropes, guy ropes, and antenna wires had to be assembled and attached before erecting the mast. This creates a considerable amount of spaghetti on the ground but with some proper management and the help of my older son, Dominic (W9KKX) the mast was erected. The mast guy ropes are attached to some nearby trees in locations high enough such that they don’t reach the ground and allow the antenna support arms to fold inward unobstructed.
Obviously to support folding, either the antenna wire has to move along the ends of the arms or I have to detach the antenna wire from the base. I’ve chosen to use a waterproof multiconductor plug to enable quick detachment of the antenna wires from the K9AY control box that will be located at the base of the antenna.
The day was drawing to a close. As I was orienting the antenna wires and attaching the arm support ropes and the guy ropes the first owl of the evening started to hoot, sounding the end of the work day. The majority of the mechanical work is complete. I need to place the antenna wires in the ends of the arms and then begin the electrical work. Thus far the design seems to be working out largely as planned. We’ll see how it holds up through the Winter. I can’t wait to “hear” this new antenna.