Thunderbolt & Lady Heather 48 hour precision survey
For the last year I've been wondering why my thunderbolt doesn't perform as
well as I thought it should. Now I know why (at least I think I know why).
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map. I tried doing a 48 hour
survey through Lady Heather and it ended a few hours ago and there is now a
huge improvement in PPS stability -no more +/- 40ns excursions. I'll be
keeping an eye on it for a bit but I think the survey helped significantly.
I'm almost sure I did a survey when I first got it but maybe I somehow
skipped over that. Anyway, hope this helps somebody.
-Bob
On Fri, Nov 26, 2010 at 6:41 AM, Robert Darlington rdarlington@gmail.comwrote:
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map.
Robert-
Are you doing this for temperature stability? How stable is it?
Dave
I'm running another test now and it's significantly improved after the 48
hour survey. Before I'd see several degree swings over the course of an
hour, now it's more like 1.1 degrees in the last 8 hours. The problem here
is I didn't do anything to the styrofoam box, but the idea was to keep
temperature swings swinging slowly. For all I know I might be fighting the
Thunderbolt.
I'm running another test under the direction of Warren S. and will post
another screen shot late tonight after I collect about 24 hrs of data with
the elevation mask set to zero degrees. I'm determined to tune this thing
to be better than it was out of the box!
-Bob
On Fri, Nov 26, 2010 at 12:41 PM, Dave hartzell hartzell@gmail.com wrote:
On Fri, Nov 26, 2010 at 6:41 AM, Robert Darlington <rdarlington@gmail.com
wrote:
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map.
Robert-
Are you doing this for temperature stability? How stable is it?
Dave
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Comes down to the simple fact that it needs to know its position accurately
in order to give you good timing. I found this one out the hard way many
(many) years ago with an old single channel Trimble unit, where we had to
manually enter a known position in order to speed up acquisition. We were in
London at BBC Broadcasting House, and I inadvertently put the longitude of
the site East instead of West of Greenwich, and wondered why my 1PPS was
ramping off!
:-)
Cheers
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Robert Darlington
Sent: 26 November 2010 6:41 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey
For the last year I've been wondering why my thunderbolt doesn't perform as
well as I thought it should. Now I know why (at least I think I know why).
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map. I tried doing a 48 hour
survey through Lady Heather and it ended a few hours ago and there is now a
huge improvement in PPS stability -no more +/- 40ns excursions. I'll be
keeping an eye on it for a bit but I think the survey helped significantly.
I'm almost sure I did a survey when I first got it but maybe I somehow
skipped over that. Anyway, hope this helps somebody.
-Bob
Careful setting the elevation mask that low. I wouldn't go below 5 degrees.
I know you want best geometry for best position determination, but there are
all sorts of effects down at those levels which will degrade your results.
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Robert Darlington
Sent: 26 November 2010 9:23 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey
I'm running another test now and it's significantly improved after the 48
hour survey. Before I'd see several degree swings over the course of an
hour, now it's more like 1.1 degrees in the last 8 hours. The problem here
is I didn't do anything to the styrofoam box, but the idea was to keep
temperature swings swinging slowly. For all I know I might be fighting the
Thunderbolt.
I'm running another test under the direction of Warren S. and will post
another screen shot late tonight after I collect about 24 hrs of data with
the elevation mask set to zero degrees. I'm determined to tune this thing
to be better than it was out of the box!
-Bob
On Fri, Nov 26, 2010 at 12:41 PM, Dave hartzell hartzell@gmail.com wrote:
On Fri, Nov 26, 2010 at 6:41 AM, Robert Darlington
<rdarlington@gmail.com
wrote:
I keep it in a styrofoam beer cooler surrounded with bottled water
in a draft free area and it's been all over the map.
Robert-
Are you doing this for temperature stability? How stable is it?
Dave
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and follow the instructions there.
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On 11/27/2010 11:33 AM, Rob Kimberley wrote:
Comes down to the simple fact that it needs to know its position accurately
in order to give you good timing. I found this one out the hard way many
(many) years ago with an old single channel Trimble unit, where we had to
manually enter a known position in order to speed up acquisition. We were in
London at BBC Broadcasting House, and I inadvertently put the longitude of
the site East instead of West of Greenwich, and wondered why my 1PPS was
ramping off!
:-)
This is quite easily understood when confronted with the basic
pseudo-range equations:
p1 = sqrt((x1-x)^2 + (y1-y)^2 + (z1-z)^2) - b
p2 = sqrt((x2-x)^2 + (y2-y)^2 + (z2-z)^2) - b
p3 = sqrt((x3-x)^2 + (y3-y)^2 + (z3-z)^2) - b
p4 = sqrt((x4-x)^2 + (y4-y)^2 + (z4-z)^2) - b
p1 is the pseudo-range to sat 1 which has position (x1, y1, z1) for the
time of observation. Similarly for sat 2, 3 and 4.
The receiver position is at (x, y, z) and the time-offset is hidden in
the pseudo-range scaled bias term b.
The better we know the receiver position (x, y, z) we can reduce the
error in estimating the b term.
Since the above equations have 4 unknowns, you need 4 birds to solve it.
While these equations are non-linear, there is a linear solution to the
above problem lurking in there. A nice little exercise with paper and pen.
Cheers,
Magnus
Hi
Of course you do have the excuse that you had to stop and think for a second as to weather it was east or west of Greenwich ...
Bob
On Nov 27, 2010, at 5:33 AM, Rob Kimberley wrote:
Comes down to the simple fact that it needs to know its position accurately
in order to give you good timing. I found this one out the hard way many
(many) years ago with an old single channel Trimble unit, where we had to
manually enter a known position in order to speed up acquisition. We were in
London at BBC Broadcasting House, and I inadvertently put the longitude of
the site East instead of West of Greenwich, and wondered why my 1PPS was
ramping off!
:-)
Cheers
Rob Kimberley
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Robert Darlington
Sent: 26 November 2010 6:41 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey
For the last year I've been wondering why my thunderbolt doesn't perform as
well as I thought it should. Now I know why (at least I think I know why).
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map. I tried doing a 48 hour
survey through Lady Heather and it ended a few hours ago and there is now a
huge improvement in PPS stability -no more +/- 40ns excursions. I'll be
keeping an eye on it for a bit but I think the survey helped significantly.
I'm almost sure I did a survey when I first got it but maybe I somehow
skipped over that. Anyway, hope this helps somebody.
-Bob
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob Camp wrote:
Hi
Of course you do have the excuse that you had to stop and think for a second as to weather it was east or west of Greenwich ...
Bob
Is it not both? It was a few degrees west, but a mere 359.5 degrees east.
Was about half a degree west as far as I can remember. The confusion
occurred (I think - long time ago), because we had to enter a minus figure
for east and a positive for west, and I got the sign wrong.
R
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of jimlux
Sent: 27 November 2010 3:31 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey
Bob Camp wrote:
Hi
Of course you do have the excuse that you had to stop and think for a
second as to weather it was east or west of Greenwich ...
Bob
Is it not both? It was a few degrees west, but a mere 359.5 degrees east.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Ah. The curse of longitude sign. The heavens-above web site used to have an explanation of why there were apparently so many users in remote western China, and on the map of user locations there was a nice outline of the US mirrored over China.
On Nov 27, 2010, at 9:01 AM, "Rob Kimberley" rk@timing-consultants.com wrote:
Was about half a degree west as far as I can remember. The confusion
occurred (I think - long time ago), because we had to enter a minus figure
for east and a positive for west, and I got the sign wrong.
R
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of jimlux
Sent: 27 November 2010 3:31 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey
Bob Camp wrote:
Hi
Of course you do have the excuse that you had to stop and think for a
second as to weather it was east or west of Greenwich ...
Bob
Is it not both? It was a few degrees west, but a mere 359.5 degrees east.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.