CCWN 75 24
                                                    
COHERENT CW NEWSLETTER (Copyrighted July 1975)

THE COHERENT TEN-TEC: Andrew L. McCaskey WA7ZVc/

         A PRACTICAL CCW STATION ASSEMBLY                         
       WA4MTP


         With continual pressure on the available spectrum for
high  frequency amateur and commercial communications channels,
the  effective employment of natural spectrum resources will
depend on the  willingness and ability of all users of the HF
spectrum to employ  methods that have not been practical in
previous years. The shift  from spark transmitters to CW
transmissions, the use of crystal  control, and modern stabilized
VFO frequency control elements have  all paid dividends in the
reduction of spectrum requirements by  improving the stability of
transmitting stations.           A corresponding improvement in
receiving systems has also enabled  more efficient use of the
available spectrum. Advances that will  permit more effective use
of the available spectrum will expand the  communications
potential of the natural spectrum resources available  to us      
    A newly developed technique that can be applied to amateur CW 
systems quite easily is the use of COHERENT CW transmitting and 
receiving systems (CCW). Several amateurs, in particular W7GHM,
have  done a great deal of theoretical and practical work in this
area. This  station is an example of the efforts within the scope
of the average  amateur's skills and finances to adapt an
existing CW station to the CCW  mode. These principles may be
extended to fit the specific situation and  equipment available
and enable conversion to CCW of most common amateur  transmitters
and receivers.           Coherent CW (CCW): A coherent CW signal
differs from a  conventional signal in the following manner.      
     (1) The CCW signal is extremely stable in frequency. For
Morse  code at 12 WPM, a coherent signal must not drift more than
1 to 2 Hz  above or below the nominal transmission frequency. A
normal CW  transmitter, VFO controlled, would be within
acceptable limits if its  drift did not exceed 100 Hz during a 15
or 20 minute operating period.           (2) A CCW signal begins
and ends at highly predictable, precise  intervals. A dit begins
at a predetermined point, will last exactly a  certain length of
time, and will end at another predetermined point in  time. A
coherent dah will have the same beginning and ending 
characteristics, but will end after a time duration precisely
three  times the length of the dit time period.