9A3KB_LF_konverter

9A3KB - A High-Performance Low Frequency Converter (by Tim Brannon WA5MD - formerly KF5CQ)

As you can see, I take SRA-3 mixer with the same performance potential (and pinout) as SBL-3. I think that TAK-5 mixer is good also. See Mini-Circuits mixers.pdf. The relay on the antenna input is used for blocking at transmission to protect sensitive device.