Measurement results and a script to view them.

- usrp/plot: convenience script to plot the signal strength scans
- usrp/step-A, usrp/step-I, usrp/step-II: signal strength scans for three
  boards

usrp/plot

@@ -0,0 +1,15 @@
+#!/bin/sh
+if [ -z "$1" ]; then
+    echo "usage: $0 file" 1>&2
+    exit 1
+fi
+if [ ! -f "$1" ]; then
+    echo "$1: not found" 1>&2
+    exit 1
+fi
+gnuplot -persist <<EOF
+set xlabel "MHz"
+set ylabel "dB"
+set yrange [-30:-20]
+plot "<sed '\$d' $1" using (\$1):(log(\$3)/log(10)*10) with lines notitle
+EOF