CCWN 75:27
                                                       
     (1) The Frequency Standard
     
     
        The frequency standard is the literal heart of the CCW
station. From  this standard all frequency and timing inputs to
the transmitter, keyer, and CCW  Filter are derived. For these
reasons, the standard is one area in which there  can be no
compromise in the quality of the components and construction
practices  employed. An excellent standard is described by  (HR,
1974). It employs a nigh  accuracy temperature compensated 4 Hz
crystal oscillator and IC dividers to  obtain 18 precision
frequency outputs in the range from 2 Mhz to 1 Hz. An  adaptation
of the standard, using the circuit board furnished by K4EEU, is
shown  in photo 2.          To complete the timing signal
requirements, an auxiliary frequency divider  board is needed in
addition to the K4EEU board to provide the 4 Khz and 40 Hz 
timing signals necessary to operate the keyer and the CCW filter.
This is  obtained by a chain of five additional 7490 dividers,
and is shown mounted  within the standard enclosure and powered
from the +5 volt regulated supply  within the frequency standard.
This auxiliary board is shown in photo 3, and  also in schematic
1. All frequency standard outputs required for the station (50 
Khz, 4 Khz, 1 Khz, and 40 Hz) appear at the phono connectors. The
transmitter  stabilization lockup signal (normally 500 Khz) is
fed through the main BNC  output, selected by the output switch
of the unit.          After initial tests using the K4EEU
standard's 1 Khz output in the  frequency stabilizer, a close
examination of the 1 Khz signal disclosed that it was 
nonsymmetrical, i.e., that the  output was at a 1 Khz rate but 
that the logic one and logic  zero levels were not in a 50%  duty
cycle. For proper operation of the frequency stabilization unit
that keeps the  TEN-TEC VFO within the tolerance required for
CC'S work, a symmetrical input      The auxiliary divider board
was expanded using a 7473 divide by 4 IC with a 4 Khz input       
as shown in the schematic.  The non-symmetrical 1 Khz output is
still very useful as a local test signal, as will be explained    
later.  The outputs of the standard must be treated carefully in
order to minimize the  transfer of TTL noise into the receiver
section of the TEN-TEC.