Timing check
    The test box applies 0V to U3 pin3 via TP9. This causes the
    micro to generate a self calibrating test pulse on TP10.
    
    The ANT Unit provides two bursts, one at frequency F1 which
    sets the timimg in motion. The second at F2 which gives a pulse out
    of the F2 comparator (TP7) the start of which should be aligned
    with the end of the test pulse. 
	Leave the scope on "ADD" at the end of the previous test and 
    the pulse will show how well the previous tests have been carried out. 
    If setting up has been careful there should be very little difference 
    observable from the previous test. 
    Re-do Tests 4 and 5 if difference spike >0.04ms (2mm on 0.2ms/cm).

