Verify period freq f1.

   Input signal is applied to the Circuit I/P and is amplified
   and drives the two tuned circuits. In Test 4 the bias on
   the comparator is set on U1 pin 5/11 so that verification
   occurs at the correct time for tuned cct L4 etc.

   This test adjusts the Drive into tuned cct L3 etc. so that it gives
   the same O/P as L4 and so with the same bias (U1 pin 11) verification
   occurs at the same time for either tuned circuits
   The O/P of the comparator is on TP5.

Fault finding:
   The bias was set ok in previous test.
   Check for a burst envelope on R14 and TP3.
   Check the O/P of U9 on TP2 - Square wave ÷ 3Vp-p
   Check for sinewave burst on the end of R9 remote from TP2.
   R11 should have 5V on one end and ÷ 0.5V on the other
   Check Q5 for correct orientation
   Check C11,C12,L3,Q5,R14,R12,C15,R17,C16 for value, and soldering faults


