to measure tranmission;
first, just use a bnc bullet as the device under test and run 'make_trans_cal.py'
 with lower, upper limits and n.  This creates a 'temp_cal.txt' file. 
Then, run 'trans_cal.py' file witha file name as the argument.  This will
create the plot and show it of the transfer function; magnitude in dB and
phase in radians
