Pluggable band modules make a lot of sense, especially in an experimental radio.
I need to look at the 4375 as I'm not familiar with it.
The Mega328P has a 15 kSa/s 10 bit ADC. That provides a 3.75 kHz Nyquist for each I &Q stream. A commutating mixer aka Tayloe detector, provides a precise quadrature output at very low cost. The effective Nyquist is 7.5 kHz. But if you don't have the compute to process them all is for nought. So adding discrete calculation of the Q stream by Hilbert transform is a complete waste of already very limited resources. There is no increase in complexity and it frees up flash.
The output of a Tayloe detector is the basis of all the sound card based SDRs and the failure to take IQ outputs from a quadrature detector a significant design gaffe in my view.
For $300 I'd expect a 2-4" 320x240 OLED, several push switch encoders and a 16 switch keypad in an extrude enclosure with metal panles. I will not use toroids in the filters because they are expensive to wind and simply not needed The entire filter block should be shielded and there is only a single filter active at any time, so the coupling problem associated with solenoid form coils doesn't exist. That's a huge cost savings and increase in manufacturability simply by using SMD standard inductors.
The key goal is a 320x240, pixel per RBW waterfall with a 1, 5, 10, 50, 100... sequence from 1 Hz to 1 kHz
Have Fun!
Reg
