Any local surveyor or civil engineering firm will know where the
benchmarks are.
Also see:
http://www.ngs.noaa.gov/cgi-bin/datasheet.prl
Don
Jim Lux
On 9/13/11 4:24 PM, li...@lazygranch.com wrote:
I think I mentioned this is a thread one before. If you are really
interested in position
Hi!
On 14 September 2011 05:36, Mark Sims hol...@hotmail.com wrote:
Lady Heather's precision (nominal 48 hour) survey collects data over
multiple 1 hour periods. With 48 hours of data, multipath and transient
disturbances are minimized. It applies weighted median filters to the data
and
Just looked up all USGS maintained benchmarks within 30 mi radius of my
home. One, at about 1.7 mi is a class A. the search site is
http://www.ngs.noaa.gov/cgi-bin/ds_radius.prl
Took me less than 5 min to find it via Google.
Don
Jim Lux
On 9/13/11 4:24 PM, li...@lazygranch.com wrote:
I think I
Often, you can talk to the local city/county and find out where some
accurate benchmarks are, typically on a curb. They are used to define
street positions and such.
I'm in Menlo Park. The USGS has a big office complex here. That includes a
bench mark just outside the front door of the
http://www.ngs.noaa.gov/cgi-bin/ds_radius.prl
is what I use. Best to check them out on google maps or earth to see
what you are getting into. Some have a summary of how to get to the marker.
I use one in a road, but it is a dead end. If it says satellite
viewable, it will be a large X.
n37
Hello, Timenutters--
There is a USGS survey benchmark on the side of the road
just a half-mile from my house.
Any guess as to how accurate these are?
I parked my pickup truck over the benchmark with the LH
box and antenna ( a 10 year-old Trimble surveyors antenna).
I only let LH run for an
Hello, Timenutters--
Somewhere I saw a LH display screen showing an AZ-EL
display of signal strength.
Looking through the help files, I do not see where to call
this display up.
I made a screen-capture of it if anyone would like to see it.
I think that feature would tell a lot about what the
I have been looking at all of these OCXO's for sale on EBAY. Most seem to
be coming out of China.
It as if they are scrapping lots of equipment and pulling out the
oscillators.
There are lots of data attached to these auctions. It seems that for an
OCXO the rate of aging changes with the
Paul,
The info they show is generally from the manual or paperwork that comes with
the OCXO when new.
If they are used OCXO's, then they will be more stable over time than a new
one, off the shelf, as far as drift, or they should be. The OCXO acts
similar to any heated device, and resistors
Howdy Timenuts-
It has been a few years since I went to school on these, and there have been
some changes. Basically, to find out the specifics on the benchmarks, you can
go
to the USGS website, and search for the benchmark, from the info on the brass
plate. You can find the 'Order' of the
On Tue, Sep 13, 2011 at 11:22 PM, Don Latham d...@montana.com wrote:
Just looked up all USGS maintained benchmarks within 30 mi radius of my
home. One, at about 1.7 mi is a class A. the search site is
http://www.ngs.noaa.gov/cgi-bin/ds_radius.prl
Took me less than 5 min to find it via Google.
When GPS was first developed (Late 70's) the DATUM used was the World
Geodetic System, 1972 (WGS-72). The next release was indeed in 1984
(WGS-84). The early GPS receivers had over 200 datums stored in permanent
memory. In its most basic form a datum defines the center of the earth and
the
Will,
Yes.. I see the point you are making. So aging is a function of all the
components in the oscillator, not just the crystal.
I am just now trying to get a feel for what to expect from different OCXO
that I have running.
Also how long to have them running before any type of meaningful
I hear that there is a hobby where people photograph these and collect
the photos. Seems pointless in the city but many are on mountain
peaks and other places with good views. The hobby is more reasonable
if you find them without using GPS. The USGS maps are good enough o
put you within 10
Hi
OCXO's are heated gizmos when in use. If you keep them on power constantly,
you are more likely to get a reasonable aging trend. When they are power
off, some (but not all) of the things that age will un-age. I have seen
some that take as long as 60 days to come back to normal after being
From a friend:
=
Any guess as to how accurate these are?
1. They vary. You have to look up the info on the particular benchmark.
Some benchmarks and geodetic monuments (see below) receive a lot of
attention and are known as First Order points. Many more receive less
attention and are
Hopefully it is better than the ones that denied Georgia a piece of
the Tennessee river - just about one mile off... Interesting topic in How
the States got their shapes on History channel.
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]
On Wed, Sep 14, 2011 at 08:39:44AM -0400, Michael Baker wrote:
Hello, Timenutters--
There is a USGS survey benchmark on the side of the road
just a half-mile from my house.
Any guess as to how accurate these are?
No guesses, but for something in the NGS, you can find
out.
On Wed, Sep 14, 2011 at 9:52 AM, Jose Camara camar...@quantacorp.com wrote:
Hopefully it is better than the ones that denied Georgia a piece of
the Tennessee river - just about one mile off... Interesting topic in How
the States got their shapes on History channel.
In one sense a BM's
Hi Chris:
And there's the problem that the BM is moving.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.End2PartyGovernment.com/
Chris Albertson wrote:
On Wed, Sep 14, 2011 at 9:52 AM, Jose Camaracamar...@quantacorp.com wrote:
Hopefully it is better than the ones that
That certainly happens, on a short time scale even, across fault lines.
Kinda makes you wonder about dams and other big structures.
-John
===
Hi Chris:
And there's the problem that the BM is moving.
Have Fun,
Brooke Clarke
___
There are of course many levels of performance in OCXOs, but in general the
ageing slows down with time, and veteran OCXOs can be very good. I recently
tested the OCXO in an old HP5245L counter (circa 1970), last calibrated in
1985, and it was still within 100ppb of 10MHz after 24 hours warmup!
Murray,
Thank you.
When an OCXO is unpowered for some time, it undergoes a further ageing
process when it starts up next. This is specified in some data sheets, and
can typically require an hour of burn-in for each day left unpowered before
specifications are met.
This is one thing I was
On 14/09/11 23:34, Paul A. Cianciolo wrote:
Murray,
Thank you.
When an OCXO is unpowered for some time, it undergoes a further ageing
process when it starts up next. This is specified in some data sheets, and
can typically require an hour of burn-in for each day left unpowered before
Maybe 2 days would be a good compromise?
I don't think you are going to get a solid answer, especially since you
haven't mentioned how good of a result you want or need.
How about recording some data and telling us what happens?
--
These are my opinions, not necessarily my employer's. I
Michael,
On 14/09/11 17:05, Michael Perrett wrote:
The user, mostly military or marine, would choose the datum he/she wanted to
use. This would match up the local map with the GPS derived position. The
difference could be quite large (hundreds of feet), especially important in
the Z (vertical)
I was speaking in terms of the user. The point I was trying to make is that
if the user had a map, chart or simply a set of three dimensional
coordinates created from one datum, then that user had better use the same
datum or position errors will be evident. The Z direction is typically used
by
This is a 3 MHz OCXO from some old telcom gear, nothing special,
First 3 hours:
http://www.megapathdsl.net/~hmurray/time-nuts/Drift-ocxo3mhz-a.gif
First 3 days:
http://www.megapathdsl.net/~hmurray/time-nuts/Drift-ocxo3mhz-b.gif
First 10 days:
Hello, TimeNutters--
Majdi asked about details on the USGS benchmark located
about 1/2 mile from my house out here in the boonies.
Below is what I have in my file on it.
Some of this means nothing to me-- my only interest in the
benchmark was knowing (roughly) how accurately it is located
for
No, more like two months! It typically takes a couple of MONTHS for an
oscillator that has not been used in a long time to stabilize! This is very
evident when firing up an old HP 5370 or Thunderbolt.This extended period
of time is why people leave their oscillators powered at all
Murray,
You hit the nail right on the head. Thank you for pointing this out.
I don't truly know what I want to accomplish, and without defining that, how
can you define what testing needs to be done.
Here are some facts.
1) I am absolutely intrigued, addicted, to the concept of precision
I forgot to mention.
I do have data for following.
The Rakon OCXO
The Spectracom 8165 WWVB Disciplined Oscillator
Ball-Efratom Rubidium Telco version
24 hours worth of data at 10 Mhz using the Z3801A 1PPS output for the
start channel
Same 24 begin and end times
-Original
As far as Lady Heather not working with other GPSDO's... well, She has
good taste. The Trimble Thunderbolt is far and away the best time-nut GPSDO
out there. It is highly configurable and controllable, comes with a very
good OCXO, and is dirt stinkin' cheap. If you dot all your i's and
A bit OT but there are way more markers out there than USGS. But getting the
official coordinates is another story. I've seen DMA (defense mapping agency),
various county markers, and I think a US Coast guard marker. I found one in
Nevada close to 100 years old. (Photographed it, but I can't
It is a hobby called benchmarking. Check it out over at geocaching.org.
I've tracked down several that hadn't been seen in many decades, updated
Uncle Sam with current coordinates (hand held gps so they can find them and
then survey it at high precision later if they want to).
-Bob
On Wed, Sep
Paul,
As far as shop temperature, I don't think you will have much of a problem,
if it only varies a few degrees +/- over the day. The concern would be if it
got as hot as, or hotter than, the oven temp, which is around 100+ degrees
F., as it's set according to the manufacturer of the OCXO.
What
On Wed, Sep 14, 2011 at 5:43 PM, Doug Calvert
dfc-l...@douglasfcalvert.net wrote:
ridiculously high performance out of the tiny little box... rivaling the
best cesium references made for under $200.
Far and away better than the M12+ or M12M?
The Oncore GPS recievers are only GPS recievers
Hal,
Wonderful plots. Thanks for posting them. Can you tell us a little
about your test setup? I think the group would enjoy hearing how
a long-term experiment like this is done.
I especially like the one-year plot since it nicely shows that even
after a couple of weeks real-world factors like
Will Matney wrote:
Paul,
The info they show is generally from the manual or paperwork that comes with
the OCXO when new.
If they are used OCXO's, then they will be more stable over time than a new
one, off the shelf, as far as drift, or they should be. The OCXO acts
similar to any heated
Bob,
It's according to what other components are mounted with the OCXO. I have
seen HP OCXO's, that are just the metal can type, mounted within a Styrofoam
enclosure, with no harmful effects. Now, if there is a board with it made to
be mounted in the free air, or where air is circulated by a fan,
Paul,
Whenever you make changes to the physical setup you will cause mechanical
disturbance to the OCXO which it is likely to take some time to recover
from. A couple of days continuous operating should suffice. Add to that an
hour for every day it's been switched off.
Even tipping the unit
Bob,
Many OCXOs, and definitely the CMAC (now RAKON) STP2145A, use ambient
compensation technology. It is not possible to place the heater, the crystal
and the temperature sensor in exactly the same place, and consequently there
will be a thermal profile within the OCXO which depends on the
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