CHU time station

hal feinstein hfeinstein at
Sat Dec 2 13:45:33 CST 2006

Back in the early 1970's, when I was a student attending a college in  
upper tier of New York State,
I had the fortunate experience to have part time employment as a data  
analyst for the college geology department.  This mostly entailed  
cleaning up field data collected by students and
faculty research, developing complicated numerical models (try) to  
explain  geophysical  phenomena.  I also was tasked with servicing  
the seismograph recorders that collected
data on the unexpectedly active seismic activity in that part of the  
country.  These seismic recorders were pretty low tech affairs.  The  
actual seismic sensing instruments were located on a bedrock platform  
out in the woods about 20 miles away and linked via audio telemetry,  
one through phone line and the other via an FM radio link.  If you  
listened to the link it sounded like a wobbly audio tone with a  
center frequency of about 1000Hz.  The data modulation was simple  
amplitude proportional to the frequency shift.  Each day I changed  
the recorder paper.  As I said, this was low tech.  The paper was  
heat sensitive and the "pen" was a hot element driven by the  
telemetry signal.  The heat sensitive paper was rolled on a drum that  
rotated slowly around.  After installing a fresh sheet onto the drum  
I tuned in CHU.  In this part of the country CHU is clear and  
strong.  The recorder had an input that caused the recording pens to  
shift the recording baseline up an inch when it detected either CHU  
on the minute tone or the second time tick for the duration of the  
tone or tick. Once I got the drum stated again I listened for the CHU  
announcer and wrote the time next to the time tick.  This is an  
important step as I will explain next.

My next task was to scan the seismography record looking for events  
that were unusual or ones we expected and were using for research  
projects.  I can recalling the local stir when we recorded the  
seismic signature of a Chinese nuclear blast, but, identifying and  
recording data for our research projects is what kept me employed.   
The main project involved earthquake prediction by studying changes  
in so called travel time curves.  These curves represented the time  
it took seismic activity to travel from known source points to our  
recording instruments. Changes in the travel time of seismic energy  
represented changes in the force compressing the rock through which  
the seismic activity travelled.  A build up in compression over say a  
year with a sudden decompression meant the subsurface forces  
compressing the rock had shifted and an earthquake was in the offing.  
The more rapid the decompression the greater the predicted magnitude  
of the quake.

Our seismic sources were the blasts detonated by mining companies  
within about 400 miles of our sensor. They also used CHU to  
accurately trigger their blast and reported to us the time, depth and  
amount of explosives used.  In turn, I located seismic signature of  
these blasts on the seismograph.  The CHU time ticks were my clock on  
the seismic recording that allowed me to figure the arrival time of  
various types of seismic waves for each of the mine blasts.   
Although  it might seem otherwise, the earth is a pretty complicated  
seismic conductor.  Some waves came right to the instrument while  
others bounced off layers deep within the earth to arrive at  
slightly  later times, something like rf multipath refraction from  
the ionosphere.   Measuring the arrival time and detonation time gave  
travel time that I plotted for the research.  About 30 mines were  
reporting in per week so I had lots of data to work on.  Its an old  
story that your research can never be better than the quality of your  
data.  Without the strong and reliable signal from CHU I'm not sure  
how we would have known the accurate time.  Other methods existed at  
that time, for example using phone lines to get accurate time but the  
expense would mean other researchers would have to do without things  
they needed. None of this was run on big budgets so CHU was an  
enabler that ought to keep enabling.  It will be a sad day to tune to  
its 7mhz frequency and hear instead some broadcaster crocking on  
about the glories of this cause or that.


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