Antenna Repair

Author: Levente Buzas

The ORCASat ground station uses high performance circularly polarized Yagi antennas. While ORCASat utilizes a half-duplex UHF communication system, equipment for VHF operation is also installed at the ground station; this is to make the installation of the antennas easier, and provide additional capabilities for amateur satellite work and future satellite missions.

The antennas selected for the ground station are the 436CP42UG UHF and 2MCP22 VHF antennas from M2 Antenna Systems Inc. These antennas were kindly made available to ORCASat at no cost by Prof. Peter Driessen VE7AB from his research laboratory. However, they were not in good condition after being exposed to the elements for ~30 years. Many elements were bent or damaged, and waterproofing on the connectors was severely degraded.

Refurbishing these antennas is an important step in the construction of the ORCASat ground station, as any deviation from the factory condition of the antenna degrades the performance characteristics (e.g. gain) specified by the manufacturer. Refurbishment involves replacing or repairing all the bent antenna elements, replacing corroded fasteners, adding aluminum antioxidant (Noalox) on all aluminum joints, and re-waterproofing all the RF connectors. As part of the refurbishment, electronic antenna polarization switching is also installed to expand the capabilities of the antennas.

Once all the elements are refurbished a jig is fashioned to store the antenna outside on the roof. The antennas are stored in this manner until they are ready to be mounted on their support structure, a topic which will be covered in an update at a later time.