This is an antenna switch I made using some relays I had that I salvaged. Internally they use a very broad set of contacts. This acts as a base that you can mount the BNC connectors in and then just glue the relays into. The relays are glued in upside down so that you can solder wires to the contacts.

I tested this using a NanoVNA and a 50 ohm dummy load. The worst SWR I got at 29 MHz was 1.38. You need to keep the wires short and make multiple paths for the ground (green wires in the photo) otherwise the SWR is very bad. At the lower frequencies like 14 MHz this is probably fine to use.

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coax_relay_switch_schrack.stl