[GPS_Standard] GPS_Standard Digest, Vol 35, Issue 1
ernieperes at aol.com
ernieperes at aol.com
Thu Jun 3 12:16:16 EDT 2010
Ref preferred GPS
Hi Gents,
Please chk the following links carefully... it is a simple but a very usable GPSDO for low budget.....
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
Best regards,
Ernie.
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Subject: GPS_Standard Digest, Vol 35, Issue 1
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oday's Topics:
1. preferred GPS (Bob Bownes)
2. Re: preferred GPS (jmfranke)
3. Re: preferred GPS (Dave Platt)
4. Re: preferred GPS (Martein Bakker)
5. Re: preferred GPS (Zack Widup)
---------------------------------------------------------------------
Message: 1
ate: Wed, 2 Jun 2010 12:54:56 -0400
rom: Bob Bownes <bownes at gmail.com>
ubject: [GPS_Standard] preferred GPS
o: undisclosed-recipients:;
essage-ID:
<AANLkTil0pggZ6cKtWOqZZVDqae_Mi_R57bSGF8waAo8k at mail.gmail.com>
ontent-Type: text/plain; charset=ISO-8859-1
So, do folks have a preferred GPS module to discipline clocks? Clearly
ome are better than others. I'd like one that will output in NMEA so
can use it to drive some other things as well, but other than that,
t has become clear that the Rockwell MicroTrack TU00 just isn't going
o cut it as it only locks to 4 satellites, has quite a bit of jitter,
oesn't hold a very good 3D lock (+/-100m just isn't good enough for
e...)
Thanks,
ob
-----------------------------
Message: 2
ate: Wed, 2 Jun 2010 13:41:41 -0400
rom: "jmfranke" <jmfranke at cox.net>
ubject: Re: [GPS_Standard] preferred GPS
o: "Bob Bownes" <bownes at gmail.com>, <gps_standard at mailman.qth.net>
essage-ID: <8D5D1A5D23804DCBAFE7DF4820552EFA at Franke>
ontent-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Speaking for myself, I have three Z3801As for serious work and several
upiter receivers for my own experiments at a GPSDO. By serious, I mean my
ouse standard which is being slowly reestablished after a house move. I
ope to have the outside antenna up and working before the end of this
onth. I have used the Jupiter receivers to discipline a couple 100 kHz
rystal oscillators. The first experiments have also included phase locking
CD4046 PLL to the 10 kHz output from the Jupiter receiver. Lots of fun!
John WA4WDL
--------------------------------------------------
rom: "Bob Bownes" <bownes at gmail.com>
ent: Wednesday, June 02, 2010 12:54 PM
o: "undisclosed-recipients:"
ubject: [GPS_Standard] preferred GPS
> So, do folks have a preferred GPS module to discipline clocks? Clearly
some are better than others. I'd like one that will output in NMEA so
I can use it to drive some other things as well, but other than that,
it has become clear that the Rockwell MicroTrack TU00 just isn't going
to cut it as it only locks to 4 satellites, has quite a bit of jitter,
doesn't hold a very good 3D lock (+/-100m just isn't good enough for
me...)
Thanks,
Bob
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Message: 3
ate: Wed, 02 Jun 2010 10:53:12 -0700
rom: Dave Platt <dplatt at radagast.org>
ubject: Re: [GPS_Standard] preferred GPS
o: Bob Bownes <bownes at gmail.com>
c: gps_standard at mailman.qth.net
essage-ID: <4C069A88.5080608 at radagast.org>
ontent-Type: text/plain; charset=ISO-8859-1
Bob Bownes wrote:
So, do folks have a preferred GPS module to discipline clocks? Clearly
some are better than others. I'd like one that will output in NMEA so
I can use it to drive some other things as well, but other than that,
it has become clear that the Rockwell MicroTrack TU00 just isn't going
to cut it as it only locks to 4 satellites, has quite a bit of jitter,
doesn't hold a very good 3D lock (+/-100m just isn't good enough for
me...)
On the used / new-old-stock market, I'd suggest looking for one
f the newer Motorola Oncore VP modules (the 8-satellite ones).
hey seem to have reasonably low (although not ideal) jitter,
nd support both NMEA and Motorola binary protocol.
Motorola made some Oncore models optimized for timing purposes
I think the UT and UT+ were of this sort) but some of these
on't speak NMEA.
The one I'm using myself is an older VP, purchased as
ew old stock from Synergy Systems a few years ago... 6
atellites, no NMEA. I was concerned about the lack of
MEA support, but the "gpsd" daemon has recently been
pgraded with a driver that understands Motorola binary
acket protocol. I had to hack the driver a bit to get
t to work - as released it understands only the
-satellite reports, and can't either request or parse
he 6-satellite reports from the older VP receivers - but
hat wasn't hard to do.
The newer VP/UT-family modules support a "site survey
nd automatic position hold" mode - they'll average
ut the positions they calculate for a day or so, then
tore the average in NVRAM and switch to position-hold
ode. This can improve the precision of the PPS
iming pulses somewhat. The older 6-channel VP modules
o support position hold but don't have the automatic
urvey-and-average feature - the average or median
osition must be determined by external software and
hen programmed back into the NVRAM before position-hold
ode can be used.
Used/working Oncore modules are pretty easily available
n eBay for a reasonable price, mostly from a number of
ell-stocked sellers in China. My impression is that a
unch of older cellphone sites (which use GPS for
iming synchronization) have been decommissioned or
pgraded, and the GPS modules pulled for sale. There
re a bunch of Motorola UT+ modules available, for
s low as $24 delivered.
Newer modules... well, the more recent Oncore line
as the M12+T, which seems to be optimized for timing
urposes... I believe it's based on one of the SiRF
hipsets. Most newer modules are *not* 5-volt - they
ypically require 3 or 3.3 volts for power, and use
his voltage for their I/O as well. Dropping one of
hese into a design intended for a 5-volt module might
ot be the simplest approach.
SparkFun has a whole bunch of modules, about which I
now little... mostly 3- or 3.3 volt, most with their
wn internal antennas (which is probably not a good
hing for this particular application).
------------------------------
Message: 4
ate: Wed, 2 Jun 2010 20:21:34 +0200
rom: "Martein Bakker" <martein at xs4all.nl>
ubject: Re: [GPS_Standard] preferred GPS
o: <gps_standard at mailman.qth.net>
essage-ID: <9C57E0CA2D2D49EBA38DFEACA990E152 at mhbp5q>
ontent-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
I am using a Rockwell Jupiter TU30-D145 easily available on ebay. It is a 12
hannel receiver and has NMEA output when configured to do so. I do not know
he specs of jitter of the 1PPS signal. I have been looking for a "Position
old" mode, but I have not found anything about it in the datasheet. Does
nyone know if this unit has a position hold mode and how it can be
ctivated?
Martein
a3ake
----- Original Message -----
rom: "Dave Platt" <dplatt at radagast.org>
o: "Bob Bownes" <bownes at gmail.com>
c: <gps_standard at mailman.qth.net>
ent: Wednesday, June 02, 2010 7:53 PM
ubject: Re: [GPS_Standard] preferred GPS
Bob Bownes wrote:
> So, do folks have a preferred GPS module to discipline clocks? Clearly
> some are better than others. I'd like one that will output in NMEA so
> I can use it to drive some other things as well, but other than that,
> it has become clear that the Rockwell MicroTrack TU00 just isn't going
> to cut it as it only locks to 4 satellites, has quite a bit of jitter,
> doesn't hold a very good 3D lock (+/-100m just isn't good enough for
> me...)
On the used / new-old-stock market, I'd suggest looking for one
of the newer Motorola Oncore VP modules (the 8-satellite ones).
They seem to have reasonably low (although not ideal) jitter,
and support both NMEA and Motorola binary protocol.
Motorola made some Oncore models optimized for timing purposes
(I think the UT and UT+ were of this sort) but some of these
don't speak NMEA.
The one I'm using myself is an older VP, purchased as
new old stock from Synergy Systems a few years ago... 6
satellites, no NMEA. I was concerned about the lack of
NMEA support, but the "gpsd" daemon has recently been
upgraded with a driver that understands Motorola binary
packet protocol. I had to hack the driver a bit to get
it to work - as released it understands only the
8-satellite reports, and can't either request or parse
the 6-satellite reports from the older VP receivers - but
that wasn't hard to do.
The newer VP/UT-family modules support a "site survey
and automatic position hold" mode - they'll average
out the positions they calculate for a day or so, then
store the average in NVRAM and switch to position-hold
mode. This can improve the precision of the PPS
timing pulses somewhat. The older 6-channel VP modules
do support position hold but don't have the automatic
survey-and-average feature - the average or median
position must be determined by external software and
then programmed back into the NVRAM before position-hold
mode can be used.
Used/working Oncore modules are pretty easily available
on eBay for a reasonable price, mostly from a number of
well-stocked sellers in China. My impression is that a
bunch of older cellphone sites (which use GPS for
timing synchronization) have been decommissioned or
upgraded, and the GPS modules pulled for sale. There
are a bunch of Motorola UT+ modules available, for
as low as $24 delivered.
Newer modules... well, the more recent Oncore line
has the M12+T, which seems to be optimized for timing
purposes... I believe it's based on one of the SiRF
chipsets. Most newer modules are *not* 5-volt - they
typically require 3 or 3.3 volts for power, and use
this voltage for their I/O as well. Dropping one of
these into a design intended for a 5-volt module might
not be the simplest approach.
SparkFun has a whole bunch of modules, about which I
know little... mostly 3- or 3.3 volt, most with their
own internal antennas (which is probably not a good
thing for this particular application).
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Message: 5
ate: Wed, 2 Jun 2010 13:41:17 -0500
rom: Zack Widup <w9sz.zack at gmail.com>
ubject: Re: [GPS_Standard] preferred GPS
o: gps_standard at mailman.qth.net
essage-ID:
<AANLkTikij1R7fbs8wu0lBRguEvg-Ha8BV_vy3flXsRw4 at mail.gmail.com>
ontent-Type: text/plain; charset=ISO-8859-1
I have a Motorola Oncore timing-quality GPS engine. I think anything that
tates timing-quality is best. I only paid something like $15 for this
ngine.
73, Zack W9SZ
On Wed, Jun 2, 2010 at 11:54 AM, Bob Bownes <bownes at gmail.com> wrote:
> So, do folks have a preferred GPS module to discipline clocks? Clearly
some are better than others. I'd like one that will output in NMEA so
I can use it to drive some other things as well, but other than that,
it has become clear that the Rockwell MicroTrack TU00 just isn't going
to cut it as it only locks to 4 satellites, has quite a bit of jitter,
doesn't hold a very good 3D lock (+/-100m just isn't good enough for
me...)
Thanks,
Bob
______________________________________________________________
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Post: mailto:GPS_Standard at mailman.qth.net
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