CCWN 75:50
                                                      
CCW STANDARDS AND SPEED

       Quite a few people have complained about the 12 wpm
standard as being too slow. First, it was selected because of the
relative ease of keying, operation of the CCW filter, and
obtaining the reference frequencies. Any pulse length could be
used as long as both the sending and receiving stations are
together on it. I have experimented with 1 second and 10 second
pulse lengths which are too slow for most people's taste. A
possibility would be to use .05 second dot lengths which would
give about 24 wpm, or .025 second which would give about 48 wpm.
Obviously, we will eventually have CCW equipment with selectable
dot lengths, and therefore speed. Meanwhile, I feel it better for
use to stay at .1 second so we can communicate among each other.
Once we have things going well, it will be a relatively easy
matter to change speeds.         Note that the digital filter
bandwidth is related to pulse length. Faster speeds result in
wider bandwidth, greater power requirements, and probably less
difference between CW and CCW.  FREQUENCY CALIBRATION BY PHASE
COMPARISONS         The usual method of calibration of a
frequency standard is to beat some harmonic of the standard on
the carrier of a HF signal from WWV or a similar station, usually
at 10 or 15 MHz. Propagation disturbances cause the received
signal to vary in phase and frequency, but these variations are
not sufficient to cause problems to most users. We usually make
comparisons over a few seconds and observe the beat. Results
obtained in this way are accurate to around 10-7 which is about
the requirement for a standard CCW station.          It is also
possible to make comparisons on the basis of phase. Phase
comparisons also have the characteristic of giving us directional
information and can relatively easily be converted into numerical
measures of moderate term accuracy.          For example, one
might compare the 10 Hz for 1000 Hz from a standard with the 600
Hz from WWV or the 1000 Hz from JJY by means of displaying both
on a single trace scope or one each on the channels of a dual
trace scope. Since there are 1000 x 60 cycles of a 1 KHz tone
over a minute, a shift of a bit less than 1 % of a cycle over a
minute in phase difference between the reference and the standard
would indicate an error of 10-7.
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