usb gps devices
Have any of the 'nuts hacked one of the very simple very cheap GPS USB
devices for your car top to see if there is an available 1 sec tick
inside one of them somewhere? I have one that I intend to look at, but
I'll have to get a scope and teenyweeny probe outside to do it, so, if
there is a readily available something, I'd like to know. Thanks!
Don
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
The pulse per second output on the Garmin serial/CMOS interface units
is only specified to be within 1 microsecond. I guess they are
commonly used to synchronize NTP servers where any extra precision
would be lost in network transport anyway.
I have been thinking of picking one up cheap to test since the
specification is so vague. 1 microsecond makes me think that the
pulse per second output is generated from a 1 MHz asynchronous clock.
On Wed, 26 Sep 2012 14:11:10 -0600 (MDT), "Don Latham"
djl@montana.com wrote:
Have any of the 'nuts hacked one of the very simple very cheap GPS USB
devices for your car top to see if there is an available 1 sec tick
inside one of them somewhere? I have one that I intend to look at, but
I'll have to get a scope and teenyweeny probe outside to do it, so, if
there is a readily available something, I'd like to know. Thanks!
Don
If they have FCC ID numbers, you may be able to find photographs of the inside of the devices, which in turn could reveal the chipset if the photo was clear, then with the chipset you could determine if a 1 second pulse is available.
Years ago I got a GPS board from Asin or something like that. It had a 1 second pulse, but absolutely not locked to gps time. So you need to beware of what looks like a timing pulse but might not be.
-----Original Message-----
From: "Don Latham" djl@montana.com
Sender: time-nuts-bounces@febo.com
Date: Wed, 26 Sep 2012 14:11:10
To: time nutstime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] usb gps devices
Have any of the 'nuts hacked one of the very simple very cheap GPS USB
devices for your car top to see if there is an available 1 sec tick
inside one of them somewhere? I have one that I intend to look at, but
I'll have to get a scope and teenyweeny probe outside to do it, so, if
there is a readily available something, I'd like to know. Thanks!
Don
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
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.
I've purchased some VERY cheap ones from eBay (china/hongkong). Some from
Motorola/ Trimble/ etc, .... Some with SiRF protocol, all with NMEA
protocol. All cheap. :-)
Just read the spec sheet on each before you buy, ...they are often in the
eBay auction, btw.
If it says the 1-pps is 'tied to' UTC time, then they will be accurate,
...mine are within 15-50ns.
Otherwise, ...like David says, ...they are not tied to the GPS clock and can
be off by microseconds.
-Don
From: "David" davidwhess@gmail.com
Sent: Wednesday, September 26, 2012 3:31 PM
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Subject: Re: [time-nuts] usb gps devices
The pulse per second output on the Garmin serial/CMOS interface units
is only specified to be within 1 microsecond. I guess they are
commonly used to synchronize NTP servers where any extra precision
would be lost in network transport anyway.
I have been thinking of picking one up cheap to test since the
specification is so vague. 1 microsecond makes me think that the
pulse per second output is generated from a 1 MHz asynchronous clock.
On Wed, 26 Sep 2012 14:11:10 -0600 (MDT), "Don Latham"
djl@montana.com wrote:
Have any of the 'nuts hacked one of the very simple very cheap GPS USB
devices for your car top to see if there is an available 1 sec tick
inside one of them somewhere? I have one that I intend to look at, but
I'll have to get a scope and teenyweeny probe outside to do it, so, if
there is a readily available something, I'd like to know. Thanks!
Don
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