change fsk filter width

src/codec2/mod.rs

@@ -106,8 +106,10 @@ impl<I: Iterator<Item = Complex>> Fsk<I> {
 
         let internal = unsafe { fsk_create_hbr(FS, 9600, M, 5, N_SYM, -1, 0) };
 
-        let fsk_lower = -FS / 2;
-        let fsk_upper = FS / 2;
+        // Set upper/lower bound on the FSK peaks, from center
+        // (Hz)
+        let fsk_lower = -10_000;
+        let fsk_upper = 10_000;
 
         unsafe { fsk_set_freq_est_limits(internal, fsk_lower, fsk_upper) };