Geoff,
I'm sorry that my comments concerning your list-serve statements were a=
pparently misinterpreted. I wasn't disagreeing with you-- only attempting =
to provide additional information about aliasing, based in my personal expe=
rience. Perhaps what you and I have learned collectively, if we can expre=
ss our thoughts without offense to one another, will be of considerable ben=
efit to the amateur community. I greatly appreciate amateur seismology, si=
nce I have received many blessings from my association with this community.=
It helped me, for example, to meet and learn from another PhD profession=
al (John Lahr) who is much better skilled at interacting with you guys than=
myself. Willie Lee, a USGS (PhD) scientist at Menlo Park, is putting toge=
ther IRIS-based materials to honor John and asked me to oversee a section c=
oncerned with a part of John's contributions to seismology. Willie and I =
didn't want to diminish the scope of those contributions by labeling them a=
s being directed toward 'amateurs'-because of the word's conotations in th=
e minds of some. I believe (and suggested to Willie) that what John has pr=
ovided fits better in the category of "Science in the public interest".
Your inference, Geoff, concerning too-many university types, I view a=
s 'right on target'. I hope that with this (too-long-for-comfort-on-my-pa=
rt) response will help you not to view me in the same context. Mercer phys=
ics is part of a College of Liberal Arts; I would rather that it be part of=
a college like other places, known as Arts and Sciences. Then the 'frict=
ional' nature of various colleagues on my career would have been less influ=
ential in causing me to lack diplomacy. This failure is bound to have be=
en made worse through my efforts to try and interact meaningfully with prof=
essional seismologists on things like 'soft-force feedback' (a question dir=
ected to me in the last 24-h, that I will respond to shortly), and 'power =
spectral densities'. Because of my insistence concerning the importance of=
these issues, and because of the indifference I sensed (whether rightly or=
wrongly) concerning the pro's response (really lack thereof)-I began, no d=
oubt, to become caustic. The famous astronomer, Fritz Zwicki was known for=
his term, "spherical bastard"-individuals who 'look the same from any view=
'. I wouldn't be surprised if I have been labeled with this term, for reas=
on of my directness. I hope that you don't believe the term fits me.
Physicists will, in my experience, engage in whole-hearted dialogue with su=
ch fervor that the un-initiated may think a 'knock down drag out fight is a=
bout to erupt'. But when the dust settles, everybody remains civil. Our s=
tyle of 'doing business' appears not to set well with the geo-science commu=
nity.
Now another few comments about aliasing and artifacts. You are correc=
t, that aliasing is a consequence of periodic sampling, no matter how it is=
done. It can be present in any system for which a high-frequency pickup s=
ignal 'bleeds through' to the 'sampler'. But the advantage of fully-digita=
l operation with the AD7745/6 chip is that it is a very small chip, and the=
refore much less vulnerable to the electromagnetic radiation associated wit=
h lines that are the most common cause for stray signal pickup responsible =
for the alias. Many if not most of you will have experienced first-hand th=
e advantage of the standard procedure of working with twisted pair wires to=
minimize 60-Hz pickup and/or ground loops. If there are no long wires to=
begin with (as with the chip mentioned) do you see thus its benefits?
(to be followed with part 2)
Geoff,
I’m sorry that my comments
concerning your list-serve statements were apparently misinterpreted. =
I
wasn’t disagreeing with you-- only attempting to provide additional
information about aliasing, based in my personal experience.
Perhaps what you and I have learned collectively, if we can express o=
ur
thoughts without offense to one another, will be of considerable benefit to=
the
amateur community. I greatly appreciate amateur seismology, since I h=
ave
received many blessings from my association with this community. &nbs=
p;It
helped me, for example, to meet and learn from another PhD professional (Jo=
hn
Lahr) who is much better skilled at interacting with you guys than
myself. Willie Lee, a USGS (PhD) scientist at Menlo Park, is putting
together IRIS-based materials to honor John and asked me to oversee a secti=
on
concerned with a part of John’s contributions to seismology. Wi=
llie
and I didn’t want to diminish the scope of those contributions =
by
labeling them as being directed toward
‘amateurs’—because of the word’s conotations =
in
the minds of some. I believe (and suggested to Willie) that what John=
has
provided fits better in the category of “Science in the public
interest”.
Your inference, Geoff,
concerning too-many university types, I view as ‘right on
target’. I hope that with this
(too-long-for-comfort-on-my-part) response will help you not to view me in =
the
same context. Mercer physics is part of a College of Liberal Arts; I
would rather that it be part of a college like other places, known as Arts =
and
Sciences. Then the ‘frictional’ nature of various
colleagues on my career would have been less influential in causing me to l=
ack
diplomacy. This failure is bound to have been made worse
through my efforts to try and interact meaningfully with professional
seismologists on things like ‘soft-force feedback’ (a question =
directed
to me in the last 24-h, that I will respond to shortly), and ‘p=
ower
spectral densities’. Because of my insistence concerning the
importance of these issues, and because of the indifference I sensed (wheth=
er
rightly or wrongly) concerning the pro’s response (really lack thereo=
f)—I
began, no doubt, to become caustic. The famous astronomer, Fritz Zwic=
ki
was known for his term, “spherical bastard”—individuals w=
ho
‘look the same from any view’. I wouldn’t be surpri=
sed
if I have been labeled with this term, for reason of my directness. I
hope that you don’t believe the term fits me.
Physicists will, in my experience, engage in whole-hea=
rted
dialogue with such fervor that the un-initiated may think a ‘knock do=
wn
drag out fight is about to erupt’. But when the dust settles,
everybody remains civil. Our style of ‘doing business’
appears not to set well with the geo-science community.
Now another few comments abou=
t
aliasing and artifacts. You are correct, that aliasing is a consequen=
ce
of periodic sampling, no matter how it is done. It can be present in =
any
system for which a high-frequency pickup signal ‘bleeds through’=
; to
the ‘sampler’. But the advantage of fully-digital operati=
on
with the AD7745/6 chip is that it is a very small chip, and therefore much =
less
vulnerable to the electromagnetic radiation associated with lines that are =
the
most common cause for stray signal pickup responsible for the alias. =
Many
if not most of you will have experienced first-hand the advantage of the
standard procedure of working with twisted pair wires to minimize 60-Hz pic=
kup
and/or ground loops. If there are no long wires to begin with (=
as
with the chip mentioned) do you see thus its benefits?
(to be followed with part 2)