Characteristics calculation site: http://www.vk2zay.net/calculators/helical.php
All calculations are on axial mode
All design files needed are available at [ the satnogs-antennas repository.
In EU cost is calculated around 35-50 euros
Mark perimetrically the boom in the ±0 position and in 240 mm distance from the base leaving a 1360 mm remainder Mark one side as side A and the other one as side B.
Using Helical-435-8-RHCP-Side_A.pdf start drilling side Α . The hole at -229 is for the 420mm struts all else are for Acetal
Β side uses Helical-435-8-RHCP-Side_B.pdf
All holes with a positive sign in side B are for Acetal and the to in -109 and -161 for the final attachment system (in our example a U-bolt) If a different support system is chosen adjustments might be required The 2 smaller diameter holes in -8 and -13 are use for the final attachment profiles of 680mm and must be 5mm
Print on a 1:1 scale Helical-435-8-RHCP-Top_pattern.pdf and place firmly on our work area. We use a 2mm 1inch (25.4mm) spaced grid mesh if it’s rolled we try to make it as flat as it gets without distorting its linear alignment.
We place the grid piece so that the boom mesh (20x20mm) trace on our print is surrounded equally by the central mesh grid space. (25.4x25.4mm) Also the linear alignment should not be identical to alignment A since it corresponds to the N-type. The reason is that the abnormal alignment will be forced during forced during the assembly
We point using a marker at the 690mm diameter. We cut the excess mesh grid and cover it with insulating film tape, to avoid hurting when handling. After the antenna placement we can remove the tape.
A construction that will assist in the configuration of the 3mm thick winding
The diameter must be strictly 225mm. This arises from the fact that the final helix diameter will be 219mm when the winding spacing is 172mm
Calculation of the 225mm
Use two chipboard pieces 20mm thick. We bonded them in one piece as pictured. Mark the perimeter with slots in it’s quadrants, preferably not in the direction of the arm.
The construction should look like a 40mm “banjo”
These instructions regard a RHCP configuration
Secure the edge of the 3mm thick brass wire together with the wood using a vise to start winding.
Winding must be performed counterclockwise as we see it so it would be clockwise from the vise to us so RHCP,
Procedure must me tight without kinks.
Mark the middle of the 680mm, and mark 10mm to the left and 10mm to the right (also helpful with the boom connection)
Drill 4mm holes at a 110mm distance from the center as pictured.
Remove part of the vertical side of the L profile from 90mm to 130mm from the central line. The cuts of the two rods must be facing each other.
Angle the boom and one of the L-profiles at a -2mm distance from the 0mm of the boom in their final position.
Mark using a long and thin mechanical pencil tip the drilling points on the L profile
Repeat the process on B with the other L-profile and drill 4mm.
The result must be symmetrical as in the provided photo.
Place the L-elements and boom on a vice and above them the mesh grid (on a probably non linear alignment) in parallel with the L-elements.
Mark upon the L-elements on both sides of the wire on at least three distances.
Overall drill at least 24 3mm holes.
Cut and remove part of the mesh grid in place for the N-type connector.
Cut the triangle out of a brass sheet of 0.3mm thickness (or slightly thicker)
Keep in mind that during cutting scale must be preserved and the extension to connect the N-type connector must be preserved.
The other protrusions are in place in order to embrace the wire.
We adapt the curvature and orientation using the "banjo"-like structure we made on a previous step.
Adjust the triangle by starting on the first mark of the wire and an orientation that conforms to Right Hand Circular Polarization (RHCP).
Stabilize the wire on the triangle by tightening the protrusions and use a torch to secure.
Remove and cut ONLY excessive part on the start of the wire based on the markings done on a previous step.
Having the boom stable gradually place the acetal elements starting from the closest to the reflector using the nylon nuts.
The placement should be every three on the top corner of the triangle.
Be cautious not to bend the wire This is probably the most difficult step, every time you screw one of the acetal elements must fix the wire on the rest.
Keep in mind that the marks must be covered in the spacer hole.
In the photo it is just before being covered by the spacer hole.
Subsequently marking with a red marker should be used for marking the final position
The remaining markers would assist in proper alignment
Checking them from the sides would place the boom exactly behind them.