Hello Jacques, and the List.
Thank you for sharing these docs.
Indeed the PPS specs of the MT3339 are confusing.
Maybe measurement on a living specimen can help?
I have a R-D 1992 counter, and a GPIB interface.
When I will have the GPS I will be able to log
some data on the PC, although I never tried to use
the Racal Counter remotely I will try.
Also I hope somebody can suggest the best way to test
the PPS from the gps using the Racal 1992, I'm not a
time nut, so I could make gross errors.
I was thinking simply to measure and log the PPS
connected to input A with the counter set to
"Period A", and 10s integration time to gain
more resolution, all this for some (many?) hours.
Fabio.
Jacques Tiete <[email protected]> ha scritto:
Hello TNutters,
maybe new thread?
you can have a look at two specsheets of the MT3339 chipset on my FTP-site
1) http://nixie.ramdac.be/TNutstuff/MT_IT530_Data_Sheet_rev_1_0.pdf
on page 8 "PPS output 100 ms high pulse, rising edge +/-1 μs @
full second GPS epoch..." so it states +/-1 μs
2) http://nixie.ramdac.be/TNutstuff/gtop module application note
-a00 _mt3339 series_.pdf
on page 32 "The accuracy level of 1PPS for GlobalTop GPS module is
within 100ns (same for majority of MTK GPS modules).
The reference design below can help improving this accuracy to
within 80ns."
but on page 14 "1PPS signal is an output pulse signal used for
timing application, its electronic characteristic are listed below:
1PPS signal and its pulse width
with 100ms duration
Low Voltage level: 0~0.4V
High Voltage level: 2.8~3.1V
Duration: 100ms (Firmware
customization for duration is available)
Period: 1s Accuracy
(jitter):10ns"
So what shall we believe?
The rest of the PDF's make a good read.
73's
Jacques
Message: 4
Date: Fri, 23 Nov 2012 16:44:27 +0100
From: Jacques Tiete <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [time-nuts] time-nuts Digest, Vol 100, Issue 95
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
About:
{
Date: Thu, 22 Nov 2012 22:26:24 +0100
From: Fabio Eboli <[email protected]>
To: [email protected]
Subject: [time-nuts] MT3339 chipset in Globaltop's FGPMMOPA6H
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
format="flowed"
Hello, while asking info about the FE5682,
I realized that for another project
(model plane data logging) I will buy
some cheap gps modules built around an
MT3339 chipset.
In my mind somewhere I stored the fact
that in the datasheet of these module
is mentioned the pps output, so I checked
and the manufacturer is claiming that it
has "High accuracy 1-PPS timing support
for Timing Applications (10ns jitter)"
This is the module I'm talking about:
http://www.mirifica.it/store/gps/342-globaltop-fgpmmopa6h-pa6h.html
http://www.alcom.be/binarydata.aspx?type=doc/GTop-FGPMMOPA6H-Datasheet-V0A.pdf
Has anybody used this chipset or similar for GPSDO?
I have no experience with discipled oscillators
but if there is any hope that the pps out
of these modules is good for the task maybe
it's time for me to start reading more about
the subject.
The final goal will be to check the timing
of the Rb I have around.
Thanks,
Fabio.
}
Hello TNutters,
I did some test with this module from Adafruit
(http://www.adafruit.com/products/746) and it seems not a bad unit.
Tested it together
with my TBolt and the PPS seems quite stable most of the time, I did
not do any logging and math on the result,
just letting the TBolt trigger the scope and apart from the cable
offset I guess 80% of the time the module was
within 10 to 15 ns.
However the specs are not very clear and it is a typical chip for
mobile use in eg. carnav stuff. I also saw some
other specs where the jitter was specified as 100ns. and even one
with a 1 microsec. so I'm a little confused.
As soon as I have some time I plan to connect this module to a
BeagleBone and do some testing for an NTP server
I think the Beagle is better for this than the RaspBerry because of
the "real" ethernet port.
Greetz,
Jacques Tiete
0499 99 83 78
[email protected]
Op 23-nov.-2012 om 00:19 heeft [email protected] het
volgende geschreven
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