EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Vgkid on May 11, 2015, 04:28:13 am
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So my ublox 6t does work(I think), it picks up satellites, gives info pertaining to those satellites, outputs both clock signals(can get both led's to lite), but when browsing the statistical view I noticed this.(pic in attachments)
When I got the unit, I was actually able to see the missing clock info. but inadvertanly then hooked it up to a psu, in which my laptop displayed usb connectivity error, and the unit rebooted. not sure if that had any affect on it.
Any thoughts?
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SUCCESS
enabled the hotfix/online-now, which reset my position correctly
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I do not have any Ublox yet but the price of 7M (30USD) and M8N (35USD) really atractive, maybe I will buy one for GPSDO.
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for a GPSDO you want a T model as it's firmware is done for timing use. They are more expensive but very good.
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I have samples of the ublox 6,7,8 M series. for $15 or $20, its a steal.
its not the timing based one but for anything short of high-end lab use, the blinking led IS a good enough PPS indicator.
I built a stratum1 timeserver based on the ublox module and a rasp pi board.
can't believe how cheap they can make gps modules now. ublox documentation is first-rate, too (that surprised me a lot).
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Used to run Stratum 1 NTP on a $8.5 u-blox 6010, really good experience I have to say.
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ublox documentation is first-rate, too (that surprised me a lot).
That's what I expect from a Swiss company which does all their GPS designs in Switzerland with their own IC designs. As of 3 years ago they were also assembled in Austria. Don't know whether they now went to China or not.....
Their customer service and application support was always first class too.
So far zero failure rate out of thousands over many years. We build commercial GPSDO's amongst other stuff and there is a measurable difference between the timing and the standard version.
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the T model is alot more "expensive" and also I got interesting rusian web talking about the 7M model
http://www.ra3apw.ru/proekty/ublox-neo-7m/ (http://www.ra3apw.ru/proekty/ublox-neo-7m/)
actually bring some idea how to deal with 30USD 7M.
my idea is use 7M card with a PLL chip and conected to this
http://www.ebay.com/itm/Efratom-Ball-814-100-2-Rubidium-Oscillator-10-MHz-Frequency-Standard-W-Heatsink-/221766448983?pt=LH_DefaultDomain_0&hash=item33a24f7757 (http://www.ebay.com/itm/Efratom-Ball-814-100-2-Rubidium-Oscillator-10-MHz-Frequency-Standard-W-Heatsink-/221766448983?pt=LH_DefaultDomain_0&hash=item33a24f7757)
and perhaps I will have a nice standard on my desk well offcourse its can not beat any "real" standard
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The board I'm using(see attachment)
the antenna: Taoglas AA.105.301111
(http://www.mouser.com/images/taoglas/images/AA_108_301111.jpg)
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Hi Vgkid,
How much You pay for the board in the state side ? the Ublox rep in Singapore ask about 100USD for 6T only not the evk-lea thats why I decide to buy 7M card wich I can buy from R/C playstore for 30USD and use UART adapter to program the output.
Thank You
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http://www.ebay.com/itm/221642672205 (http://www.ebay.com/itm/221642672205)
the 7m module on ebay in the US.
good seller. bought lots of small items from him and its fast shipping, usually gets to me across to the west coast in 2 or 3 days. bought maybe 5 or 6 neoblox modules from him. there's an 8m, as well but I really dont quite get what all the diffs are between 6,7,8. spec sheets show very slight improvements but I suspect its mostly internals and firmware that is inside.
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I'm confused, which is not an unusual situation. There are Chinese ebay sites like this one:http://www.ebay.com/itm/Ublox-LEA-6T-GPS-Module-w-Compass-for-APM2-5-APM2-6-Flight-Controller-Multirotor-/121648208865?pt=LH_DefaultDomain_0&hash=item1c52cc5be1 (http://www.ebay.com/itm/Ublox-LEA-6T-GPS-Module-w-Compass-for-APM2-5-APM2-6-Flight-Controller-Multirotor-/121648208865?pt=LH_DefaultDomain_0&hash=item1c52cc5be1)
That sell LEA-6T for toy nav, are these more suitable for GPSDO timing? That is are they better than regular ublox?
Edit: I guess I should refine my question, LEA-6T does indeed seem like a more expensive timing oriented gps why is it being sold for cheap RC toy application? There must be something I'm missing .
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I paid $70.xx on Taobao, don't ask about shipping. I got several other items.
seller info:
http://item.taobao.com/item.htm?spm=a230r.1.14.1.l8DdsK&id=40118177741&ns=1&abbucket=7#detail (http://item.taobao.com/item.htm?spm=a230r.1.14.1.l8DdsK&id=40118177741&ns=1&abbucket=7#detail)
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Hi
"because my Indo-English doesn't work very well please forgive me if my post is make everything get worst than clear anything"
The data sheet of Ublox 6T say it use TCXO for precission timing
https://www.u-blox.com/images/downloads/Product_Docs/LEA-NEO-6T_ProductSummary_%28GPS.G6-HW-09020%29.pdf (https://www.u-blox.com/images/downloads/Product_Docs/LEA-NEO-6T_ProductSummary_%28GPS.G6-HW-09020%29.pdf)
How good /precisse is that I don't have clue yet.
but a website made a measurement about the "next generation" of Ublox specially the 7M
http://www.ra3apw.ru/proekty/ublox-neo-7m/ (http://www.ra3apw.ru/proekty/ublox-neo-7m/) (no I don't understand Russia either but google translate help me to understand)
from their measurement the phase and spurious is not good so their purposed to use the module/card with a PLL to control OCXO for a higher quality GPSDO.
Thank You
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If you use a regular PLL then you can use any GPS module. I hope you are aware that the 1PPS signal has a sawtooth "overlay" and that a distorted GPS signal will throw your reference off too. If you want to get in the 10E-11 range and better and also want to have a reliably stable source you can't use regular PLL's to do that.
The worst solutions are those who use GPS modules which continue the 1PPS output when they lost lock to the satellite. Their 1PPS then drifts with the internal TCXO. Your reference is then as accurate as the TCXO (usually 0.5ppm).
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The good thing about the 6t is that you can set it to either continue the 1pps output(or other frequency) or no output ifthe signal is lost. The funniest thing is that with my antenna stuck to my desk, I always have a fix.
seller link:
http://item.taobao.com/item.htm?spm=a230r.1.14.1.l8DdsK&id=40118177741&ns=1&abbucket=7#detail (http://item.taobao.com/item.htm?spm=a230r.1.14.1.l8DdsK&id=40118177741&ns=1&abbucket=7#detail)
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If you do plan on using a non(T) model go with the N specced ones, they have the tcxo option.
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Hi Kjs,
I believe You mean I can not use the 1 PPS signal in the regular PLL to lock OCXO/XO is that correct ?
for Ublox 6T / M7N / M8N they use TCXO and use NCO for generating any freq you want but unfortunately the result is bad like the Russia web I mention before rell about.
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Hi Kjs,
I believe You mean I can not use the 1 PPS signal in the regular PLL to lock OCXO/XO is that correct ?
for Ublox 6T / M7N / M8N they use TCXO and use NCO for generating any freq you want but unfortunately the result is bad like the Russia web I mention before rell about.
yes, correct. A real GPSDO is a lot more complicated than what you can see in many of the hobbyist solutions out there. Unfortunately that requires some pretty specialized equipment to be able to measure it. The 1PPS of the -T is really good but the higher frequencies not that much. It still requires that you run with a sophisticated Kalman filter to compensate for the known deficiencies of GPS modules and GPS itself. The "frequency and phase" measurement isn't as simple as a phase comparator either.
Won't be able to log in here for the next 7-8 weeks as I start a big move in the next hour and the PC's will be taken down. Last posting for a while.......