A good ham friend of mine, is blind, yet would like to have an antenna, that would allow the auto tuner in his HF radio, to be able to tune one antenna for several of the low HF bands, without any trouble.
This project is a 4 band (75,40,20,15) meter Maypole I'm building for him. I've gone to great detail, showing how to construct the hexagon platform. Once installed I will follow up with additional pictures. (click on pictures for larger image)
Start the project with a 1 foot by 1 foot piece of 1/4 inch Plexiglass
Divide the Plexiglass square into 4 equal squares. Find the center of each square, and lay out a circle, about 5 3/4 inch in diameter, using a divider.
Layout the circumference of each circle, using the radius as the dimension, to achieve a hexagon pattern. hint: use a felt tip pen, attached to a common set of dividers, by means of electrical tape. this allows you to easily see the layout marks.
Close up of one of the 4 squares.
Cut out all 4 hexagons, and debur all sides. then, clean all sides with something like lava soap and scotch brite. that prepares all the surfaces for a good glue bond.
I used super glue, to bond the 4 hexagons.
Allow 24 hours to dry. then, use a sander, to true up all 6 sides. this is not absolutely necessary, but it sure looks better. Layout the center mounting hole, as well as the 6 (1/4) holes that will become the wire terminals. I used a 3/4 inch hole, for the center mounting bolt. more on that later.
note: the next picture will be a roll of copper plumbers tape, I use for the straps. If you get this material, then just use the hole pattern thats already on the copper strap, to lay out the 6 holes for the 1/4 inch bolts.
Copper type strap, often called plumbers tape.
Solder the copper straps, while they are loosely bolted to the platform.
Be sure to clean the
areas of the copper straps to be soldered. Clean the bolt hole
regions, for good electrical continuity.
(Note: You will need a heafty soldering iron, or 250 Watt soldering gun for this. The heat does not seem to bother the Plexiglass.)
This soldered area, will become the attach points, for the coax connections.
Top view of the platform, with 1/4 inch stainless nuts on top of stainless washers. the bolts are also stainless steel, with stainless steel lock washers on the bottom side, to ensure good electrical bonding to the copper strap. additional washers & nuts will be necessary, once the antenna wires are fitted to the bolts.
Establish the area that will become the lower pole surface, then outside of this area, drill 2 holes slightly larger than the coax. I used RG-58CU, so the holes I drilled were .200 inch.
Make a lazy half bend with the coax, on the top of the platform.
Separate back, about 3 inches, the center conductor from the shield. I used heat shrink on both conductors; this is worth taking the time to do. Next solder each of them to the centers of each strap junction.
Apply epoxy around both holes on top of the platform, where the coax exits and re enters.
Also apply epoxy around the bottom holes, where the coax enters and exits. (not shown in picture)
This step is not essential, but due to concerns over lightning, I added a short(10") length of stainless steel whip with a large ball bearing welded to it. I welded a 3/8 by 24 thread nut to the top of the 3/4 inch mounting bolt. This will allow a direct path, above the platform, for lightning to ground, thru the push-up pole.
Bottom view of the antenna platform, mounted to the top of the push-up pole. I haven't yet, taped the coax to the pole, but at final assembly, I'll be sure to tape the coax to the push up pole. this lessens the stress put on the coax.
This is a top view of the completed 4 band Maypole platform. Remember,
15 meters will work, because its the 3rd harmonic of 40 meters.
There will be a set of wires for 75 meters, a set for 40
meters, and a set for 20 meters. I haven't shown the detail for the wire
preparation, so please refer to the original Maypole platform project,
to view the method of wire preparation. You will also find the formula for
determining the wire lengths.
(Note the Lightening Rod is in place)
The finished antenna as installed: