I'm having problems with my scratch-built 40m superheterodyne receiver based on the W7ZOI design. Using a 4.195 MHz IF with a crystal ladder filter, but getting intermittent oscillation in the IF strip. MC1350P IF amp with proper decoupling, but still breaks into oscillation around S9 signals.

Anyone experienced similar issues? Wondering if it's insufficient isolation between stages or feedback through the power supply. Currently running 12V with 100uF + 0.1uF decoupling at each stage.

AGC is functioning properly, so I don't think that's the culprit. Would appreciate any troubleshooting suggestions from fellow homebrewers.

Classic problem with high-gain IF strips. Add ferrite beads on the power leads to each IF stage - FB43-101 or similar. Also check your shield compartments between stages. I had the exact same issue and ferrites solved it completely.

Had similar oscillation with my homebrew 20m rig. Try reducing the IF gain slightly with a 10k pot in series with the AGC line. Sometimes the MC1350P runs too hot with strong signals even with proper AGC.

Check your crystal filter termination impedances too. Mismatched impedances can cause instability in the IF chain. What's your measured filter bandwidth and insertion loss?