Antenna switch relay board
The relay board is the part of the overall system that does the actual coax switching. The design is freely available here https://m0agx.eu/2021/04/03/coax-relay-pcb-for-hf-antenna-switching/ You can send the gerber files to any manufacturer to get cheap PCBs. The board has 4 relays and 5 SO-239 connectors. Coils can operate both with positive and negative common wire (depending which way the diodes are placed).