CCWN 75:56
                                                   
          I am working on a new type of CCW filter. It is
designed
to work at 9 MHz. No BFO is necessary. The circuit is
similar to the Petit filter but it uses faster IC's and a
switch frequency of 36 MHz. This frequency is obtained from
a highly stable oscillator which has a slight VFO capability
for fine tuning, about 15 Hz. It may turn out to be necessary
to lock this oscillator to a stable 4 MHZ oscillator. The
filter also has selectable pulse length and provisions for
ordinary CW are to be included, although the advantages of
CCW would not be there. The filter also has adjustable
bandwidth. I will describe it later in CCWN.

          An important accessary is a simple diode mixer with
outputs
for a volt meter and audio. This is used for calibration, e.g.,
feeding a signal from the station standard (e.g., 2 MHz) and
a signal to be calibrated (e.g., l8 MHZ ) to the mixer. The
audio output is used to get the calibration close, and a volt
meter is used for low beat frequency observation. Sometimes
it is better to use a communication receiver tuned to the
frequency of interest.
















Figure 1. Block diagram of the W6NEY CW-CCW receiver