CCWN 75:20
                                                              

     The steady tone output should also have a very light, rapid
clicking       sound in the background. If you have provided
balance controls, adjust them       alternately for the best
null. Rotate the phase select switch over its       entire range.
No noticeable change in output should occur at any position.     
      Now introduce a very small signal input at precisely the
center frequency       of the filter. (This is exactly h the
frequency of the TTL switching signal used       for the input
mixer.) The level of this input should be from 10 to 30
millivolts.       Whenever this signal is connected, you should
hear a pronounced rise in the       amplitude of the audio
output, and this output will be noticeably delayed from the      
input when you connect and disconnect it.            If you now
connect a low-level non-coherent signal from your receiver into 
     the filter, you should hear low-level, random pulsing tones
in the output.            When operating the filter on the air,
it is extremely important that the       desired signal level not
exceed about 50 millivolts. Otherwise, the filter will be      
saturated and will not function properly. Undesired signals can
be permitted to       reach 1 or 2 volts, and the filter will
reject them satisfactorily.            The CCW filter can provide
an a.g.c. voltage which is compatible with the i.f.      
amplifier shown in Wes Hayward's CCW receiver (CCWN 75:3). If
four diodes are       connected to pins, 1, 7, 8, and 14 of the
output LM324 as shown in Figure 5, this       output plus a
simple operational amplifier buffer will provide an excellent
gain       control.            On-the-air operation is simple,
and exacting. Both the frequency of the       incoming signal and
the timing of the signal must be precisely matched to your      
receiver frequency and the filter timing. If you are using a
receiver in which every       frequency-generating circuit is
phase locked onto your 4-Mhz master standard (such       as the
CCWN Coherent receiver design), and you have your standard set
precisely to       WWV, the only adjustment you need to make is
the filter timing, with the 10 position       phase control.     
      Our standard procedure for a station calling CQ is to send
a string of dits for       at least 30 seconds followed by "CQ DE
W7GHM." If you hear a sudden rise in filter       output which
lasts for more than a second or two (either a steady tone, a
pulsing       tone, or a dit string), adjust the phase control
for maximum contrast between the       spaces and the dits. You
now are synchronized, and when he calls, "CQ" you should hear     
 it clearly.