Can I put two of these cheap (less than 3USD) and common CFU455IT +/-2kHz (4kHz bandwith -6dB ) ceramic filters in series to get a lower bandwidth good for SSB TX? If I'm correct I will get -12dB at +/-2kHz so the bandwidth will be reduced a bit, I can trim the rest by adding a trimmer in parallel to the filters and playing with the loading resistor. What about CFU455HT? They are even more easy to get and cost 1.25USD. It sure beats paying 50USD for a factory made one and I have only so much crystals to put in filters.
When making an SSB superhet RX are lightly loaded (100k ohms) LC resonant circuits and RC lowpass audio filters good on their own or do I really need that filter?