CCWN 76:72
PHASE ADJUSTMENT BY TIME REFERENCE Chas.. Woodson
Previously I suggested (CCWN 75:22) adjusting the phase
of CCWN keying to UT the world time standard. In testing the
practical method designed by Tyrrell (CCWN^I 76:69) for doing so
we have found a major problem. The signals do not reach the
receiver instantaneously. For example, JA signals take about .05
second to reach '16. Our adjustment, when we are using .1 second
pulse length, needs to be within .91 second for most effective
reception. Note that the phase lag from UT (assuming
the sender is in phase with UT) give us a measure of the distance
the operator is from us. This means, if this method becomes
widely used In CCW, CCW operators will in principle be able to
out the distance covered By the RF path. TUTORIAL: 'WHAT IS CCW?
A simplified ANSWER Chas. Woodson 1. Suppose we divide
seconds (in UT) into tenths. We can use 'WWV or a similar station
as a reference. Note that the seconds begin at the same time no
matter where you are on earth. 2. Suppose Morse CW is
sent in a very regular fashion, and such that each dot begins
exactly at the beginning of a tenth of a second and continues for
a tenth of a second. Therefore, the person wishing to receive the
CCW signal will know when each time period occurs, and during
each of these periods the transmitter will be sending either a
dot or a blank. A dash would be three times as long as a dot and
also begin at the beginning of a tenth of a second. All spaces
would be multiples of these .1 second periods. 3. In
our receiver, we amplify the signal received and mix it with a
local oscillator signal of the desired frequency in a mixer
designed to allow output of DC voltages. The output of the mixer
is zero Hz ( a DC voltage which is a function of signal strength)
for the desired frequency, and 10 Hz for an interfering station
(or noise) 10 cycles away. 4. We then integrate (sum)
the signal over each .1 second period. For the desired frequency,
this may be thought of as the sum of the signal and the noise
voltage measured at very small intervals throughout the .1 second
period. For the 10 Hz away interfering station (or noise 10 Hz
away), the sum would be zero because the average of 1 cycle (.1
second of 10 Hz) is zero. For noise at the frequency of 20 cycles
away from our station frequency, the noise will go through 2
cycles in the .1 second period of averaging, the average
intensity of the output of the filter will be zero for such
noise. O In the Petit filter, this sum from .1 second
is used to control the intensity of the audio output for the next
.1 second. Thus, the intensity of the audio output is constant
for .1 second. Since noise is varying in a seemingly random
fashion over the .1 second, the average of the noise over this
period is much lower than the average over say .O01 second. The
received power of the desired signal is relatively constant over
the .1 second period. The result is that the relative effects
upon the output intensity of the noise and the signal is greatly
changed, with the effect of noise dramatically reduced. We are
comparing the average noise + signal for a .1 second period, with
the average noise for a .1 second period.