This is an antenna switch I made using some relays I purchased off AliExpress. The relay model number is SRD-24VDC-SL-C. 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 1.20. This is substantially better than my prior effort. You need to keep the wires short and make multiple paths for the ground otherwise the SWR is very bad. At lower frequencies (less than 5 MHz) this is fine to use.

This takes about an hour to assemble. I think this is a neat project, but it may not be worth building if you can buy a commerically available antenna switch.

One possible improvement is to mount this switch on a grounded piece of sheet metal to inccrease the shielding.

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