I developed a mixer topology that’s based on the familiar quad diode balanced mixer, but using FST3257 SPDT CMOS bus switches instead of diodes. Initial results are very encouraging, with conversion loss under 4.5db and IP3 at least +30 dbm. Transformers are 4 turns #34 trifalar twisted wire on BN43-2402 cores. I’ll write more about this later…
. Stay tuned.
Breadboard
Bus Switch Mixer Schematic
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Conversion Loss @2db/div
W3JDR Bright Ideas 
Darren
Check that the transformer are wound exactly as specified and that bias voltage is 2.5V I’ve built several of these and the conversion loss at HF is always around 4.5 dB.