On 4/4/12 7:35 AM, Chuck Forsberg WA7KGX N2469R wrote:
If foliage does such a number on GPS signals, just fill a big garbage bag
with yard debris and set the antenna in the middle of that.
*wet* yard debris..
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A google of helibowl GPS turns up dozens..
But here's a reference that might be useful to the tinkerer:
M
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and follow the
Oops hit send accidentally..
Charles Counselman, Multipath-Rejecting GPS antennas, IEEE Proceedings,
V87, #1, Jan 1999, pp 86-91
The antenna in the paper is one approach, but of more interest are the
references..
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On 4/3/12 5:22 AM, Azelio Boriani wrote:
Agreed. My consideration was general but, yes, money is necessary so a
decision is a must to properly allocate the financial resources.
Well.. we could hope for a fabulously wealthy patron who thinks that it
would be a good thing to fund time-nuts of
On 4/2/12 12:19 AM, Hal Murray wrote:
robert8...@yahoo.co.uk said:
Have a look in The Art of Electronics by Horrowitz Hill (if you don't
hav a copy, you should! or try the local libary). It has a nice circuit for
this (Actually a telescope drive IIRC) type of application.
Rats. I can't
On 4/1/12 3:01 AM, Dr. David Kirkby wrote:
On 03/31/12 09:38 PM, Jim Lux wrote:
On 3/31/12 1:15 PM, Brooke Clarke wrote:
Hi Achim:
SMA RF connectors have a very limited life (number of matings) until
they are worn out.
I don't think so. Yes, they're only rated for 500 cycles, but there's
On 4/1/12 2:25 PM, Dr. David Kirkby wrote:
On 04/ 1/12 03:33 PM, Jim Lux wrote:
On 4/1/12 3:01 AM, Dr. David Kirkby wrote:
On 03/31/12 09:38 PM, Jim Lux wrote:
I don't think so. Yes, they're only rated for 500 cycles, but there's a
paper by a guy at Maury Microwave that I ran across when
On 3/31/12 1:08 PM, Javier Serrano wrote:
On Sat, Mar 31, 2012 at 9:24 PM, Achim Vollhardtavoll...@physik.uzh.ch wrote:
I do work in high energy physics and we use LEMO and other standards. For
some years now, I have started to advertise against LEMO (in particular the
LEMO 00 size), as it is
On 3/31/12 8:21 AM, Eric Lemmon wrote:
Hal,
The beauty of the header strips is that the Z3801A can easily and quickly be
converted back to RS-422 in the future, without having to partially
dismantle the unit and do more soldering- again.
true, but you have to remove the board from the case
On 3/31/12 1:46 PM, J. Forster wrote:
Remember, there are two varieties of SMA: Those with a gold plated center
pin soldered onto the center conductor and those with a sharpened center
conductor of 0.141 hard line.
The latter are near junk, IMO.
Only if you're planning on multiple
On 3/31/12 3:24 PM, Hal Murray wrote:
jim...@earthlink.net said:
I can't see ever changing mine back. I could see going in and modifying it
to put a USB/serial dongle inside, so it would have a USB jack on it, since
serial ports are become less common.
I have several USB-Serial dongles.
On 3/30/12 4:16 PM, Javier Herrero wrote:
I suppose that when it was photographed, nobody noticed it. After
noticed that it was no correctly plugged-in, the past pictures were
reviewed and found that in fact it was not fully plugged in :)
We do this all the time at JPL. You have someone come
On 3/30/12 8:43 PM, Larry McDavid wrote:
On 2/16/2012 Brad Stockdale announced here on Time-Nuts that he had a HP
Z3801A GPSDO for sale. I corresponded with Brad several times and he
reported that he sold one Z3801A to a list member and that this unit had
been modified to provide RS-232 rather
On 3/29/12 3:17 PM, Magnus Danielson wrote:
just so we can re-transmit it, is probably not sensible. However,
studies of these remarkable pulsars is ongoing.
Hmm, wouldn't the space-located antenna have a good chance of better S/N
as the antenna sees cold space and could be kept cold itself?
On 3/29/12 6:19 PM, Tom Knox wrote:
I thought I might apologize because I didn't explain my idea very
well initially, and reiterate my original thoughts on a pulsar timing
idea. The basis of my idea was that if problems could be overcome
certain pulsars could provide not only Time but also
On 3/28/12 1:28 AM, Jim Palfreyman wrote:
So when a member of the general public says:
Why do we need really accurate clocks?
What is your answer?
Personally I explain that accurate clocks enable you to pack a higher data
rate into your smart phone. They like that.
But I don't know that
On 3/28/12 1:28 AM, Jim Palfreyman wrote:
So when a member of the general public says:
Why do we need really accurate clocks?
Not necessarily at time-nuts performance, but here's some clock and
clock distribution applications
There are a lot of systems out there that timestamp something
On 3/28/12 1:11 PM, Tom Knox wrote:
My thought was to rec it in space before it is degraded and perhaps rec it in
the x-ray region. A few Geo Sync Sats doing a correction algorithm for earth
position vs the pulsars would not be that complex.
Thomas Knox
What you're talking about is
On 3/21/12 9:17 AM, beale wrote:
I suppose there is limited interest in homebrew GPS receivers given how cheap
the fully integrated chipsets are. However, just noticed the below tuner chip
intended for DTV, actually lists GPS L1 as an applicable frequency. A TV Tuner
USB stick using this
On 3/16/12 5:35 AM, Chuck Harris wrote:
I was of the understanding that SBIR's results are in
the public domain that however, doesn't mean that
a patented receiver that uses the SBIR results cannot
be had.
You too can use the results of this SBIR and patent
your receiver's special features.
On 3/14/12 9:14 PM, J. Forster wrote:
On 3/14/12 8:07 PM, J. Forster wrote:
John
Like your thought. I seem to remember costas loops work like that to
recover the carrier.
Paul,
It recovers a bipolar signal to steer the local VCO as well as the
data..
It also needs a quadratue hybrid at the
On 3/15/12 6:50 AM, shali...@gmail.com wrote:
Poul-Henning,
Do you need 16 bits or can you get by with a 12 bit ADC?
Have you considered using an FPGA for signal processing? It seems you need a
fairly serious CPU to handle that much data.
You could use an FPGA, but the data rate isn't all
On 3/15/12 7:49 AM, J. Forster wrote:
Suppose the modulation is not present. The output of the phase detector
that steers the local standard ot indicator works correctly.
Now reverse the 60 kHz carrier. The phase detector works exactly thye
opposite way... wrong.
Now alternate between 0 and
On 3/15/12 8:10 AM, J. Forster wrote:
Why make it simple when complicated also works?
-John
Can't get your doctorate doing something someone else has already
done...grin
Enormous literature out there on this, and it's been grist for many a
Master's or PhD dissertation.
All in a quest
On 3/15/12 3:24 PM, Chris Albertson wrote:
On Thu, Mar 15, 2012 at 2:51 PM, Attila Kinaliatt...@kinali.ch wrote:
After the discussion here, i had a similar idea. I want to use the
STM32F4xx for something bigger and bought two discovery boards to get
used to them. But i didn't know what i want
On 3/15/12 3:27 PM, Poul-Henning Kamp wrote:
In messagePine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you
On 3/15/12 9:41 PM, Chris Albertson wrote:
On Thu, Mar 15, 2012 at 8:45 PM, Jim Luxjim...@earthlink.net wrote:
http://dttsp.sourceforge.net/
documentation for dttsp is less than wonderful
On 3/14/12 6:23 AM, Attila Kinali wrote:
On Wed, 14 Mar 2012 14:05:03 +0100
Azelio Borianiazelio.bori...@screen.it wrote:
And don't forget the usual PDF
http://gpstime.com/files/tow-time2011.pdfwhere you can find the
comparison of typical Allan Deviations from various
clocks on page 7.
On 3/14/12 8:07 PM, J. Forster wrote:
John
Like your thought. I seem to remember costas loops work like that to
recover the carrier.
Paul,
It recovers a bipolar signal to steer the local VCO as well as the data..
It also needs a quadratue hybrid at the VCO frequency (although it might
be
On 3/12/12 2:20 AM, Azelio Boriani wrote:
Yes, build three and compare them but your comparator has to have a very
low noise floor. I think that in addition to building new higher precision
clocks you need to build new lower noise TI counters.
This is part of the thrill (or frustration) of
On 3/10/12 2:42 PM, Azelio Boriani wrote:
Amazing, 10 at -19... will it ever be measurable?
build three and compare them?
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I've got a student intern (Undergrad Senior) who's doing a project for
me where he's trying to synchronize (and syntonize) two 1 pps ticks,
generated from different oscillators using some modules in an FPGA.
One oscillator is a run of the mill 66 MHz clock oscillator the other is
a 49.x MHz
On 3/7/12 10:22 AM, saidj...@aol.com wrote:
Sorry for my language, I was quite upset when I read his letter.
If it really was trivial and very low cost to upgrade GPS receivers, then
he should not worry too much about loosing much revenue. This sounds more
like he made major investments in
On 3/5/12 2:31 AM, Charles P. Steinmetz wrote:
Poul-Henning wrote:
That would make roll-out a matter not for governments, but for
airports, harbours and other interested parties, like for instance
DME.
Would this mean depending on private parties for precision timing and
positioning [using
On 3/5/12 3:45 AM, Poul-Henning Kamp wrote:
In message20120305113804.48fc411b...@karen.lavabit.com, Charles P. Steinmet
z writes:
Technical merit aside, I doubt there is any chance of getting
regulatory approval for such a system, at least in the US, for
practical and political reasons.
On 3/5/12 6:19 AM, Charles P. Steinmetz wrote:
Poul-Henning wrote:
Thats why some people in the military is looking into a modern
more lightweight version of Tactical Loran for use when GPS is jammed.
That is a much easier thing -- our military/intelligence complex
(however oxymoronic that
On 3/3/12 4:13 PM, Azelio Boriani wrote:
Geez, I have read and I don't think it is possible to replicate the CALOC
PDP-8/E software nor it is useful to use the Austron 5000 Loran receiver,
my understanding is that it was used to control and steer the system. It
seems they were in use until the
On 2/29/12 4:20 PM, Bob Camp wrote:
Hi
They look like part of an eval kit. The docs on the kit might be out there.
Bob
Like this
http://www.analog.com/en/content/CU_AD9850_evaluation_tools/fca.html
The part has been around a while
* AD9850 Evaluation Board Software for Windows 3.1
On 2/28/12 3:40 PM, Chuck Forsberg WA7KGX N2469R wrote:
Does this mean your GPS is safe? Who knows.
http://dailycaller.com/2012/02/28/lightsquared-ceo-resigns-amid-revelations-of-companys-proximity-to-obama-white-house/
well, L2 did just announce they're laying off half their staff (of some
On 2/23/12 6:24 AM, Alberto di Bene wrote:
On 2/23/2012 1:04 AM, Poul-Henning Kamp wrote:
I simply don't buy the story that tightening the connector makes
a consistent 60 nanoseconds difference on a signal.
I spoke with a physicist of Cern, friend of the leader of the team that
On 2/23/12 1:25 PM, Robert LaJeunesse wrote:
FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem
(seen in eevblog teardown). Yes it's sort of cheating, but if the part works
fine because all of the suppliers parts now yeild that fast due to an improved
process well,
On 2/23/12 2:22 PM, Azelio Boriani wrote:
Actually, undersampling does use the alias effect to bring down the RF
carrier. That is, the direct sampling radio concept cannot avoid the
aliasing: it is exploited to avoid, for example, to sample a 2GHz carrier
modulated with a 20MHz signal with a
On 2/22/12 4:38 PM, Dr. David Kirkby wrote:
On the train this morning I picked up a copy of the Metro (there are
usually numerous copies on any train, as its free and does not take long
to read).
There was an article about financial institutions being concerned about
the time of their clocks
On 2/22/12 2:26 PM, Poul-Henning Kamp wrote:
In message9a458dba-3875-43b2-8383-5ca2f86be...@leapsecond.com, Tom Van Baak
(lab) writes:
Could be on the electrical side of the adapter, not the optical
side. It's not impossible to get 60 ns of phase or trigger error
with RF connectors.
I
On 2/20/12 8:34 AM, Achim Vollhardt wrote:
Hi Bill,
what about White Rabbit?
http://www.ohwr.org/projects/white-rabbit/wiki/Description
Successor of NTP.. PTP: precision time protocol.
It delivers Gigabit Ethernet and precise (1nsec) timing over singlemode
fiber. You would have to connect all
On 2/20/12 9:52 AM, WarrenS wrote:
Recording high speed and/or long general purpose raw Osc data, the file can
become very large.
I'm looking for a simple, fast and easy (and cheap) way to transfer large
compressed data files of up to say a 100 MB between time-nuts.
I know there are all kinds
On 2/20/12 10:31 AM, Bob Camp wrote:
Hi
Simple answer:
A rack mount cesium standard is as good as you can get. Figure on 15 ns per day of
drift. That gets you to 15 us in 1000 days. You may or may not get one that drifts
that little, a lot depends on little details. For 3 years, consider
Do you believe there may be a problem for those who are
reverse-engineering, and posting on the open net, items which may be
covered under these regulations?
If you do, you may want to consider contacting them off-list and letting
them know your concern.
Peter
Man, export controls are a
On 2/19/12 2:47 PM, Tom Van Baak wrote:
There seems to be some confusion about stability and drift; about
ADEV and other tools. The tone of this thread is not heading in a
positive direction.
So instead I will offer to put together a short tutorial or series of
tutorials that focus on factual
On 2/17/12 5:27 AM, paul swed wrote:
The used market makes no difference to them. No revenue stream.
In fact I would say you are swatting at the behive. It would be wise to
leave them alone since several have reached out and already had a poor
experience.
As someone else pointed out this is what
On 2/17/12 7:02 AM, Bill Riches wrote:
Good points made - no income for the company, However on the other side of
the coin - look at Agilient having available all of the old HP manuals for
download even though there is no income to them. I wonder if it was a
requirement of them to supply HP
On 2/15/12 7:16 AM, Peter Vince wrote:
See:
http://www.nytimes.com/2012/02/15/business/media/fcc-bars-airwave-use-for-broadband-plan.html?_r=1scp=3sq=lightsquaredst=cse
Err.. not necessarily. As one of the commentators in the business press
said yesterday (paraphrasing).. Harbinger needs
On 2/11/12 7:42 AM, paul swed wrote:
Indeed interesting but the 5370s seem to go for $300-400 and this $1750.
I had been lucky to get my 5370s pre-interest price accelerator so $50-75.
Because who would ever want such a heavy thing?
Much as I love the modern interfaces, size, quite, and low
On 2/11/12 12:43 AM, Attila Kinali wrote:
Moin,
The recent discussions have made it again clear to me, that i lack
a lot of knowledge in electronics. Especially when it comes to
the black arts: analog stuff, HF, getting the most ouf of a transistor,
or doing it really really low noise.
Could
On 2/11/12 8:00 PM, Said Jackson wrote:
The appnotes from LT especially Jim Williams articles. LT used to print these
in book form.
Check out the V to F designs, and the data acquisition stuff. Very practical
with real world components and test results. Very high end analog stuff.
Most
On 2/10/12 1:37 AM, Hal Murray wrote:
It's the international science and engineering fair, so both kinds show
up.
The line between applied science and engineering is pretty fuzzy.
There is another category. I'm not sure what the right term is. How about
just having fun?
Most
On 2/10/12 2:05 AM, Chris Dawes wrote:
Thanks Hal,
Will have to visit next time I am in San Fran sounds interesting
Makes a nice, but busy, day to do the Exploratorium and the California
Academy of Sciences/Steinhart Aquarium. They're pretty close to each
other, so it's not like you have
On 2/9/12 4:51 AM, WarrenS wrote:
Indeed,
ADEV is for random freq variation not easily measured by other means.
Temperature fluctuations do not cause random freq changes and the
temperature's effect should be removed if one wants accurate long term
ADEV numbers.
Even daily diurnal cycles due to
On 2/9/12 8:42 AM, Magnus Danielson wrote:
On 02/09/2012 04:10 PM, Jim Lux wrote:
Interesting point you make here. The rising ADEV at 100-1000 second-ish
tau in a system that should be better is a classic sign (at least around
here) that temperature effects are showing up.
I regularly see
On 2/9/12 8:23 AM, Chris Albertson wrote:
I think it's odd that all these science projects are NOT doing any
science. They sound like engineering to me.
So you build a neat mouse trap? That is not science unless you have a
theory about mouse behavior and your trap is intended to test the
Yes, a fun project, and a fine physics lab exercise. But not a good
science fair project because it doesn't meet the originality bar.
This is something that I confess I had a hard time figuring out what
that meant when I was entering science fairs... as it happened, my
projects *were*
On 2/9/12 4:00 PM, Bill Hawkins wrote:
Fellow time scientists,
Here's my view of the difference between science and engineering:
snip
If marketing studies show a positive return on investment, engineers
are turned loose to solve the problems revealed as the details of
building or
On 2/8/12 3:23 PM, EB4APL wrote:
I want to take advantage of the topic just to ask if anybody has any
manual or schematics of the PTS 040. I realize that the PTS 160 is close
enough, taking in account the different frequency range, and they use
almost the same modules but it would be nice to
On 2/8/12 4:51 PM, Magnus Danielson wrote:
On 02/08/2012 03:25 PM, Craig S McCartney wrote:
We already have one of those that everybody can use. It's called the
earth.
Yes, but you don't have it hanging in a neat position in your office,
living room or lab, now do you? Besides, if you are a
On 2/8/12 4:47 PM, EB4APL wrote:
Jim,
I already have the info on the remote interface, taken from the PTS 160
doc and other sources, I was asking if he was talking about some
specific gadget.
I also was using at those years some remotely controlled PTS's , did you
know the JPL MK IV receiver
While delayed, I would think that the signal freqs would still need to
be maintained... hmmm, maybe not... interesting science project...
anyone? anyone? ;-)
Jerry
I'm waiting to see a good time-nuts project at the science fair. (at any
level up to ISEF)
There's a lot of good
On 2/8/12 6:03 PM, Chris Albertson wrote:
The number one TN science fair project would have to be measuring the
speed of light using some simple, inexpensive method such as
reflecting sunlight from rotating mirrors
Actually, that's probably not a good project: it's been done, in almost
On 2/8/12 7:37 PM, Ray Xu wrote:
Hi guys
My 2 cents...from first person experience ;-) (although this doesn't have
much to do with frequency standard-related science fair projects...)
I am actually a high school junior in one of Dallas/Ft Worth, Texas's,
suburbs, and I have been competing in
On 2/8/12 8:11 PM, Ed Palmer wrote:
I thought the same thing but I think Mark was referring to the end date
of the Mayan calender. Now those guys were Time-Nuts!!
But oddly, as Feynman pointed out, they only used Venus, and not Mars
(or Jupiter, although the synodic period is pretty long for
On 2/7/12 1:30 PM, Attila Kinali wrote:
On Tue, 07 Feb 2012 16:15:44 -0500
Mike Naruta AA8Ka...@comcast.net wrote:
On 02/07/2012 03:59 PM, Attila Kinali wrote:
while TV and radio uses 75R. (there was once a reason
for this, but i don't know it).
A 4:1 balun takes old 300 ohm twinlead to 75
On 2/7/12 6:01 PM, Chris Albertson wrote:
GPS requires a good view of the sky, Hard to do in say the 7th floor
of a 40 story building if you have no windows. I'm wondering about
using the new digital TV signals for timing.
I'm pretty sure there is time code in the signal and I'm pretty sure
On 2/6/12 6:14 AM, paul swed wrote:
Indeed the long cable runs are tough. Though today we have differential
cable drivers that do quite well to the Ghz range. But certainly back in
the dark ages the sine wave was a very reasonable way to go.
Regards
Paul
we may have GHz bandwidth drivers, but
On 2/6/12 6:47 AM, paul swed wrote:
Well right you are thats why todays chips have equalizers and such.
But then its all getting crazy complicated even though its in a itty bitty
chip.
My distribution is made of high quality television analog amps and I have
in general made amplifiers and such
On 2/2/12 1:49 AM, Hal Murray wrote:
If I want to decode a GPS signal, do I have to know (or figure out) the
frequency of the local oscillator? Or does it drop out of the calculations,
somehow?
Yes, it comes out in the calculations.
That's why you need 4 satellites. You solve for x,y,z
On 2/2/12 1:28 AM, Attila Kinali wrote:
On Wed, 01 Feb 2012 21:53:16 -0800
Jim Luxjim...@earthlink.net wrote:
You don't need the ADC: you just need a limiter/comparator.
Yes, but this degrades sensitivity quite a lot.
You don't need insane sampling rates. Think in terms of subharmonic
On 2/2/12 12:05 PM, Daniel Schultz wrote:
I found this homebrew GPS receiver project recently:
http://www.holmea.demon.co.uk/GPS/Main.htm
No custom specialized chips that are unavailable in small quantities, or which
will go obsolete in a few months. I think the best solution for the open
On 2/2/12 9:39 AM, Attila Kinali wrote:
On Thu, 02 Feb 2012 07:49:53 -0800
Jim Luxjim...@earthlink.net wrote:
[
There is a sampling rate around 38-39 MHz that works out nicely for all
three bands (actually, any rate in that range probably works..I haven't
looked).. It helps that the 3 GPS
On 2/1/12 9:27 AM, Chris Albertson wrote:
On Wed, Feb 1, 2012 at 8:19 AM, Attila Kinaliatt...@kinali.ch wrote:
On Wed, 01 Feb 2012 09:07:23 -0500
John Ackermann N8URj...@febo.com wrote:
There've been numerous threads on the Gnuradio mailing list about code
to receive GPS using the Ettus
On 2/1/12 10:12 AM, Attila Kinali wrote:
On Wed, 1 Feb 2012 09:27:30 -0800
Chris Albertsonalbertson.ch...@gmail.com wrote:
I thought it might be interresting but then found out you need to buy
$2,000+ worth of hardware for even start experimenting.Open Source
SDR needs to run on a common
On 2/1/12 12:22 PM, Attila Kinali wrote:
On Wed, 1 Feb 2012 11:49:51 -0800
Peter Montapmo...@gmail.com wrote:
One possible inexpensive design:
- RF input passively split three ways, with LC filters for the three
channels: L5/E5, L2, and L1/E1/Glonass
- For each channel, a downconverter
On 1/31/12 12:34 PM, cfo wrote:
On Mon, 30 Jan 2012 19:23:10 +, cfo wrote:
I just got my Prologix GPIB-ETH
I am 90% Linux Ubuntu based , and would like to get 99% based. So i am
looking for some C code examples, implementing the linux networking
part.
Thanx for all the suggestions ,
On 1/26/12 10:14 AM, Chris Albertson wrote:
On Wed, Jan 25, 2012 at 8:38 PM, Jim Luxjim...@earthlink.net wrote:
OK.. without getting into celestial navigation, the whole thing of telling
time with the moon is intriguing. And with some forethought and data
available today, we could fairly
On 1/26/12 2:08 PM, paul swed wrote:
We are talking parts in the -9th but I am using a hp3801 and the general
software that lets you see the 1 sec variation.
I had never seen this behavior before and thought the oscillator must be in
trouble. Measured it against a local RB and it was stable.
On 1/26/12 2:55 PM, Jim Palfreyman wrote:
As a reasonably experienced occultation observer (and the very reason I got
into being a time-nut - so I could time these observations), the main
problem is that the number of binocular-observable occultations is actually
quite rare. When the star
On 1/26/12 4:35 PM, Jim Lux wrote:
Yeah, that is something I don't have a feel for.. How many stars are
candidates? I assume you could get a moon RA/declination list, and then
run that against the star list.
This is one of those things that I was hoping there's probably someone
who has
OK.. without getting into celestial navigation, the whole thing of
telling time with the moon is intriguing. And with some forethought and
data available today, we could fairly easily do what folks back in the
18th century could not.
Let's say you run a suitable celestial model and identify
On 1/25/12 8:38 PM, Jim Lux wrote:
OK.. without getting into celestial navigation, the whole thing of
telling time with the moon is intriguing. And with some forethought and
data available today, we could fairly easily do what folks back in the
18th century could not.
Let's say you run
On 1/24/12 9:48 AM, Chris Albertson wrote:
If you want to try your hand at position determination in the pre
radio nav days you can buy a studen sextent It's a low cost plastic
instrument sells for about $60.
That's the Davis Mark 3 (which is basically a copy of a lifeboat
sextant). $50 from
On 1/24/12 9:46 AM, Attila Kinali wrote:
On Tue, 24 Jan 2012 11:05:58 -0600
Lee Mushelherbe...@centurytel.net wrote:
If you're looking for a really interesting topic to read about, the
development of an accurate ship-board clock is really fascinating! And it
wasn't done overnight!
If you
On 1/24/12 10:26 AM, Chris Albertson wrote:
have you ever tried to measure an angular distance using a hand held
instrument while standing on the deck of a moving boat in the open
ocean? try it and you will see why they wanted a clock. You
really can't measure an arc minute reliably we
On 1/24/12 3:19 PM, J. Forster wrote:
Is the USNO almana/ephemeris still published in hard copy every year? That
had moon timing, etc.
You can download pieces from the Astronomical Applications website at USNO.
Or you can buy a copy of the Nautical Almanac for about $20 from a
variety of
On 1/23/12 6:58 AM, Chuck Harris wrote:
I don't think it is clear that editing the Subject line is the same as
raising a new subject. There are a bunch of reasons why you might want
to edit a subject line on a thread without starting a new thread: Removing
offensive material, fixing a spelling
On 1/23/12 9:45 AM, J. Forster wrote:
The fundamental problem is our system of units is not defined rationally.
What is universal about a meter or a second or a kilogram? Nothing!
If you were suddenly transported elsewhere in the universe bareassed,
could you replicate the standards we use?
If
This chat of zenith cams, etc. is interesting.
How well could you do with something like the camera in the iPhone4
facing up. The front camera is VGA resolution.
Say you're on another planet?
(we transfer time to Mars Rovers using radio, but techniques that are
independent of radio are
On 1/23/12 12:05 PM, Poul-Henning Kamp wrote:
In message4f1dbcc9.9040...@earthlink.net, Jim Lux writes:
How well could you do with something like the camera in the iPhone4
facing up. The front camera is VGA resolution.
Very badly.
The major trouble is actually not getting the light from
On 1/23/12 12:29 PM, Chris Albertson wrote:
On Mon, Jan 23, 2012 at 12:02 PM, Jim Luxjim...@earthlink.net wrote:
This chat of zenith cams, etc. is interesting.
How well could you do with something like the camera in the iPhone4 facing
up. The front camera is VGA resolution.
Say you're on
On 1/23/12 1:18 PM, Javier Herrero wrote:
El 23/01/2012 21:43, Jim Lux escribió:
One is where you lay the iphone on the table in a fixed position.
One could use the internal accelerometers to determine level, but I
don't think you could tell orientation, unless, perhaps, you can see
On 1/23/12 1:20 PM, Doug Millar wrote:
A mercury mirror is better than a plumb bob.
Doug
Or Gallium?
But what sort of precision are we looking for here?
1 second of earth rotation is 1/240th degree (15 arc seconds), about
0.07 milliradian.
So on a plumb bob a meter long, you're looking
So, to summarize the chain so far..
You need to solve two problems:
What's my camera orientation with respect to the stars.
Where is the Sun (or something else) as it moves across the field.
Conceptually, if I have my camera fixed and look at stars over some
hours, they'll follow a path that's
On 1/23/12 3:27 PM, Brooke Clarke wrote:
Hi Jim:
I spent quite some time on looking at ways to optically tell the time, see:
http://www.prc68.com/I/StellarTime.shtml
Oddly, I was *just* looking at that page...I mean, I closed the browser
and opened mail and saw your email.
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