Nothing wrong with a channel approach. Simplifies most of the design
tradeoffs.

BTW, I measured all the AM stations at my house (Seattle). Using a
typical AM radio (a Sony SW7600GR with internal antenna), I tuned all
the stations that were easily received without too much QRN/QRM (day
time). I then checked the field strength of each using a spectrum
analyzer and a calibrated antenna with 1 meter effective electrical
length.

I received 15 (reasonably clear) stations. The strongest station,
only 2 miles away, gave -55dBuV (about 1.8mV/m), while the weakest of
the 15, gave -85dBuV (about 56uV/m).

QRN, due to skywave, increased substantially at night. This is "same
channel" interference, which we get from the fact that there are no
"clear channels" anymore. Better antennas actually make the QRN worse
on some channels-- even while helping local daytime reception.

I would design the radio to only work with strong local signals, if
fidelity is the goal.

Again, I say "good luck."

Steve.

--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA