usrp: adjust outlier rejection and signal range for improved antennas

- usrp/evscan: reduce outlier limit from 10 dB to 5 dB
- usrp/plscan: raise lower bound from -40 dB to -30 dB

usrp/evscan

@@ -19,5 +19,5 @@ for f in "$1"/24*; do
     echo -n `basename "$f"` ''
     for n in "$f"/data*; do
 	./fft $opts -s 100 0 20 70 <"$n" || echo "fft failed for $n" 1>&1
-    done | ./range -v 10
+    done | ./range -v 5
 done

usrp/plscan

@@ -19,7 +19,7 @@ gnuplot -persist <<EOF
 set xlabel "MHz"
 set ylabel "dB"
 set xrange [2402:2483]
-set yrange [-40:-5]
+set yrange [-30:-5]
 set title "Received signal strength"
 set data style errorlines
 plot \