Re: Low Band Receiving aerials.
A few years back I built a prototype SDR transceiver capable of full break-in CW keying.
I used it with the CW Skimmer program in the CQ WW CW QRP Assisted section to become 2nd in the UK. No one was more surprised than me!
For the antenna change over relay I used a small Omron surface mount relay that had a very fast switching time including contact bounce of 3 mS. In other equipment I've run them at 150 W on HfF with very good isolation and VSWR performance.
Here is a link to the RS Components listing for the relay: https://uk.rs-online.com/web/p/high-frequency-rf-relays/8074107/