2m Amateur Radio Cycloid Omni-Directional Antenna

grabcad

This is a model of a Amateur Radio Cycloid Omni-Directional Antenna designed for the 2 meter VHF band (135 ~ 150 MHz) using 1/2" copper piping. This antenna uses a Linear Loading of the feed line into the the antenna. This design was found on the WA7X website but was designed by Clint (KA7OEI) http://www.ka7oei.com/and has a very detailed explanation of the design : http://www.wa7x.com/cycloid_info.htmlI have enhanced the design by using a PCB at the matching area to support the connector and have better contact with the tube contacts. The coax connector should be soldered to the PCB and the traces on the PCB should be designed and tuned as 50 ohm impedance microstrips that are a differential (balanced) pair across the top and bottom.The other enhancement is a 3D printed antenna support to the mast. I also designed for (2) set screws to put pressure on the tube to keep them in place. The side set screws are nylon 3.5 mm but can be #6 screws as well. There is only one 8 mm mounting bolt that is also nylon but can be 5/16 as well. I have checked for the center-of-mass for the model, and the position is just right for the balance of mass to avoid vibration issues.I recommend a 90 degree (right angle) N-type connector adapter to LMR-400 coaxial cabling that runs to the mast and a tight spiral around the mast about 6 ~ 8 times to serve as a 'choke-blaun' and to provide a strain-relief for the coax to the feed point at the circuit board (PCB).This antenna can be designed for other bands such as GMRS, FRS, or MURS.(update : 1/6/2022) : i am investigating changing this design to space the feed copper pipes to 300 ohms and use a twin-lead wire feed from a BalUn lower down the mast similar to the feed method that i used in the halo antenna model. I believe that a balanced 300 twin-lead feed will dramatically reduce the EMI issues concerning feed this type of antenna with a coaxial cable feed which requires the use of clamp on ferrites filters or the typical choke BalUn that is used ubiquitously. However the twin-lead feed will need to be outside and lower than the NEAR-field radiation pattern to be effective. Using 3d printed cable supports for the twin-lead into the mast will lower the conductance (G) losses as well.