CC;C ,5:44
RECEIVER DESIGN FOR CCW Ray Petit & Chas Woodson

           Considering the characteristics of CCW and the
experience we have had so far, we offer the following ideas for
the design of a multi-band, multi-frequency CCW receiver. Let's
call it the PW-1 design.             The receiver should be
single conversion. This simplifies the frequency stability
problem. We think 9 MHz for the IF is a good choice as good
crystal filters are available. Experience with the Hayward design
(CCWN 75:3) indicates it needs more selectivity. Both the HFO and
the BFO should be phase locked. Figure 1 gives a block diagram of
the phase locked HFO for such a receiver and Figure 2 gives a
block diagram of such a receiver.             We propose the new
net frequencies of 3,562,500 Hz and 14,062,500 Hz. These
frequencies are selected because they are relatively easy to
synthesize.             Figure 1 shows the proposed design for
the HFO of 5,062,500 Hz. National Semiconductor makes an
integrated circuit well suited for this application, the DI375,
which has an oscillator and TTL buffer on one chip.            
Another LM375 plus the other half of the 7474, another quarter of
the 7486, and some discretes make up the 9,001,000 Hz phase
locked BFO. The X-OR has one input direct from the 1 KHz output
from the standard, the other from the D flip-flop is the
difference between the 9th harmonic of 1 MHz and the 9,000,000 Hz
output from the Xtal BFO.             For 14,062,500 Hz output,
the transmitter needs the existing 5,062,500 Hz HFO and 9,000,000
Hz for the carrier oscillator. The 9,0Q0,000 Hz is easy to get by
an xtal oscillator connected to a 7490 with QA and QD outputs
connected to R01 and R02, this yields a divide by 9. The 1,000 Hz
output is phase- compared with the 1,000 Hz from the standard,
low pass filtered, and applied to the tuning diode of the
oscillator as above.             For 3,562,500 Hz output, the HFO
needed is 12,562,500. A 500 Hz signal intO the clock of the D
flip flop will strip off the 12,5 MHz, leaving the 62.5 KHz as
before.      We welcome your comments and suggestions.