Helical Antenna, 2.0 - 2.7 GHz, RHCP, 10 dBi

4 turn Right Hand Circular Polarised (RHCP) helical antenna. Designed and optimised for the 2000 to 2700 MHz frequency band, 10 dBi gain, 51 degrees beamwidth and VSWR less than 2:1 across the band.

Dimensional accuracy and dielectric properties influence antenna performance at these wavelengths. Antenna design & optimisation assumed a dielectric constant of 2.1 for PLA material and 100% infill.

The as-built antenna exhibited a higher measured VSWR of 2.26:1 at 2000 MHz, reducing to 2:1 or less over the 2016 to 2700 MHz frequency range and resonant at 2098 MHz where the VSWR is 1.44:1.

###Slicing/Printing

I printed my antenna with eSun Arctic White PLA+

* 100% infill must be used. * 0.4 mm nozzle must be used. * Brim recommended.

For dimensional checks the printed tube diameter should be close to 27.09 mm, helix pitch 30.52 mm and the matching section 2.45 mm above the tube base.

For a Left Hand Circular Polarised (LHCP) antenna apply your slicer's X or Y axis mirror function.

###Parts I Used:

* 200 mm Diameter Aluminium Pizza Tray - Amazon Australia ASIN B07N8RCGB9 * SMA Female Panel Mount Connector - Amazon Australia ASIN B0CX4PJXQ2 * Tinned Copper Wire, 0.71 mm / 22 AWG - Jaycar CAT.NO WW4030 * M3 x 12 mm Nylon Screw - Jaycar CAT.NO HP0140 * M3 nut & washer (metal or nylon OK)

###Suggested Assembly Steps & Tips:

1. Start winding the tinned wire at the top of the tube. Make a small (~3 mm) right angle bend then hook and glue into the small hole. 2. Wind the wire tightly, following the helical groove, all the way down and OVER the SMA connector cut-out at the bottom. I used masking tape to hold the wire in place as I went. 3. Secure the wire with a thin bead of super glue along its length, allow glue to fully cure. 4. Mark & centre punch the centre of the reflector (pizza tray), mark & centre punch a second position 13.5mm from the first. 5. Drill a 3.5 mm diameter hole in the centre of the reflector and a 6.5 mm diameter hole at the second off-centre position. 6. Deburr holes on both sides and lightly sandpaper around the 6.5 mm hole for a good electrical bond to the SMA connector. 7. Insert the SMA connector and fasten into position. Try to maintain the SMA connector's hexagonal nut in the orientation indicated in the supplied images. 8. Cut and needle file the SMA's connection pin so the wire element makes a right-angle connection while remaining parallel with the reflector surface. Almost all of the pin needs to be removed, leaving approx. 0.5 mm protruding above the dielectric. The pin is brittle; work slowly and with a light hand. 9. Perform an alignment check of the helical element and reflector assemblies, adjust pin height and rotation of SMA as required. 10. Fasten the helical antenna element in position with the M3 nylon screw (screw inserted down the tube, nut & washer installed from behind the reflector). I also applied super glue between tube base and reflector before tightening the screw. 11. Solder the wire to what remains of the pin with minimum amount of solder, snip off excess wire. The gap between the wire and top of SMA connector should be very small (~ 0.2 - 0.3 mm). 12. Perform SMA pin to antenna element electrical continuity check and SMA pin to SMA body electrical isolation check. 13. Glue the end cap into position.