I'm planning a scratch-built QRP SSB transceiver covering 80, 40, 30, 20, 17, 15, 12, and 10 meter bands with about 5W output. Planning to use a single-IF design with AGC, and looking at Si5351 for the VFO. My main questions: What's a good IF frequency that has readily available crystal filters? I've seen 455 KHz mentioned often but crystal sources seem scarce. Also considering a 7 MHz IF with ladder filter using MC1496 mixers and IRF840 finals. Any recommendations for a proven filter design at this frequency?

For multi-band QRP work, I'd strongly recommend 9 MHz IF - plenty of crystal filter options available and you can get good selectivity with relatively simple ladder filters. The MC1496 mixers work well at this frequency too.

As a newcomer to homebrew, I found separate receiver and transmitter builds helped me learn before tackling a full transceiver. Maybe start with just the receiver section first? The VFO tracking between RX and TX can be tricky.

The Si5351 is solid for this application - I've used it in similar builds. For the transmitter chain, Steve Weber's design is hard to beat and gives clean 4-6W output across all HF bands. Consider his low-pass filter board design too.