[Elecraft] RX Ant Preamps and the K3 12v Accessory Jack

[Phil & Debbie Salas]

"...I would suggest that you consider using a Reed relay or similar fast 
acting relay to short circuit the external preamp's input during transmit 
periods..."

Take a look at the Omron signal relay, Mouser part number 
653-G6A-274P40-DC12.  These relays operate in 3ms typical, 5ms max.  I use 
them in my ALS-600 QSK conversion and they work great.

Phil - AD5X