[time-nuts] Has anybody checked this? GPSDO in kit

Bryan _ bpl521 at outlook.com
Sun Oct 30 09:57:55 UTC 2016


>>

 <<    e) Which is the antenna signal level (dBm) that this unit require
<<to operate properly?>>


The antenna you referenced should be fine. I would hazard to guess<g> that antennas a re a whole separate topic. The gain should be fine. What you need is a clear unobstructed view of the sky. That can be challenging depending on your location. Note that you will likely need some different connectors as the antenna looks to have a "N" type connector. You should also try and use cabling that I suitable and does not cause significant signal loss.


As for splitting remember that it is a active antenna and expects 5 volts so not sure if the Wilkinson splitter would work??. I would be interested as to what others have to say about splitting the antenna. Have read that a common television satellite antenna splitter commonly found on Ebay can be used, but the impedance may be 75 ohms and the connectors would have to be changed.


<<     b) which is the difference between the Symmetrical and Trimble
<<unit? I am mostly interested in interfacing, like the ability to get
<<also NMEA sentences (if possible) and the ability to add the KOBB
<<display. In the thread there    are a lot of information but really not
<<sure how much is common between the two. Only sure thing I have
<<understood seems that Trimble does not initiate a Survey at power on.


I had the Symmetricom so can't tell you much about the difference other that from what other posters have contributed they are very close to if not identical in many respects.Not having to complete another survey on power up is a definite plus on the Trimble, but I found that it can complete a survey on the Symmetricom quite quickly.


There is a number of serial ports on these boards. Looking at the fifth picture on the ebay link, at the top left corner next to the SMA connector just below R13 is a vertical row of holes. That is the main serial connection and it is at TTL levels. There is other serial connections available on a ribbon like connector at the end of the board. Posts on the EEVBlog show where and the pins on the ribbon connector and what they do. One poster on EEVblog probed the ribbon connector and identified the pins. http://tipok.org.ua/node/53. Some of the UART are high voltage, others TTL

[http://tipok.org.ua/sites/default/files/gps_rx_lores.jpg]<http://tipok.org.ua/node/53>

Trimble/Symmetricom UCCM GPS Receiver 50-pin connector ...<http://tipok.org.ua/node/53>
tipok.org.ua
Introduction. This page describes the pinouts of 50-pin connector, avaliable at "Trimble 57963-C" and "Symmetricom UCCM 089-03861-02" boards, which can be bought on Ebay.




Unfortunately they don't show the backside of the board in the Ebay link, but I strongly suspect as the main serial connection does not look populated by any wiring in the picture, they are tapping into the rx pin of the GPS receiver as the source for one of the RS232 connectors. This is a source of NMEA statements and is documented on the EEVblog. You can't send any commands put it does send out a continuous stream of useful NMEA commands that make it a ideal source for a DIY project to add a display. Once you receive your unit and connect it to your pc you will (should) see a stream of NMEA commands from one of the RS232 ports.


Hope this helps. I unfortunately toasted mine, and was contemplating about picking up another one.




-=Bryan=-


________________________________
From: time-nuts <time-nuts-bounces at febo.com> on behalf of Giuseppe Marullo <giuseppe at marullo.it>
Sent: October 29, 2016 11:10 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Has anybody checked this? GPSDO in kit

I ended up buying a pre-cooked Trimble plus a missilehead-like GPS antenna:

http://www.ebay.it/itm/252162780444?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Trimble GPS Receiver GPSDO 10MHz 1PPS GPS Disciplined Clock with rs232 port | eBay<http://www.ebay.it/itm/252162780444?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT>
www.ebay.it
Trimble GPS Receiver GPSDO 10MHz 1PPS GPS Disciplined Clock with rs232 port | | eBay!



http://www.ebay.it/itm/262679152903?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
PCTEL GPS (L1) 26dB TIMING ANTENNA KIT GPS-TMG-26N W/ Mount Kit | eBay<http://www.ebay.it/itm/262679152903?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT>
www.ebay.it
PCTEL GPS (L1) 26dB TIMING ANTENNA KIT GPS-TMG-26N W/ Mount Kit | | eBay!




This should limit the chance it would be a DOA(well I hope at least), it
comes already boxed, has somewhat a wide power supply voltage range, no
pigtails to play with, and the antenna is new.

Now I just need to prepare the cable for the antenna, the mounting pole
and wait them to arrive through snail mail.

Many thanks to all but especially to Larry McDavid W6FUB that helped me
a lot to decide.

Now, while I wait...

1) I am reading the thread on EEVBlog(Thanks Bob and Bryan), (I have
like one month before I receive the unit so I could have spent more, I
admit) but I have several questions:

     a) Is this a board or a puzzle? seems that brings reverse
engineering to a whole new level. 32 pages of forum posts looking for
missing parts...LOL

     b) which is the difference between the Symmetrical and Trimble
unit? I am mostly interested in interfacing, like the ability to get
also NMEA sentences (if possible) and the ability to add the KOBB
display. In the thread there    are a lot of information but really not
sure how much is common between the two. Only sure thing I have
understood seems that Trimble does not initiate a Survey at power on.

     c) since I *may* like to use the GPS antenna also for the clock
kit(I WANT a DISPLAY!), I would like to build/buy a *simple* spitter.
Just a second output. I hope that a passive cheap schematic would do.
BTW, on which frequencies this unit receive data? Just 1575.42MHz? Would
it be possible to build a Wilkinson splitter?

     d) still confused about the number of serial ports available, their
expected usage and voltage levels.

     e) Which is the antenna signal level (dBm) that this unit require
to operate properly?


Giuseppe Marullo
IW2JWW - JN45RQ

On 10/24/2016 1:05 AM, Giuseppe Marullo wrote:
> Hello Attila,
>
> not cheap at that point, and I already have that ST board(I live few
> km from ST headquarters, BTW)!.
>
> Still licking my wounds from Eclipse-whatever chaintool, ouch, no way
> I am going to mess with that again anytime soon.
>
> I am not in the mood to start another endless project, way too many
> unfinished stull in my drawers(as many others I guess).
>
> I like the qrp-kit kit, but I will have a good look at eevb for the
> "thunderbolt in disguise" and then I will decide.
>
> Thanks.
>
> Giuseppe Marullo
>
> IW2JWW - JN45RQ
>
>
>
>
> On 10/23/2016 5:52 PM, Attila Kinali wrote:
>> On Sun, 23 Oct 2016 15:32:33 +0200
>> Giuseppe Marullo <giuseppe at marullo.it> wrote:
>>
>>> I am puzzled about what to do, still the total cost of it for a OXCO +
>>> GPS(unit with antenna) + control mcu is 67usd, I doubt I could find
>>> anything like this for a cheaper price new.
>> Yes, it's cheap for a kit, but it is not that cheap if you want to be
>> cheap. :-)
>>
>> You can get GPS modules for as low as $5 on ebay (these are new),
>> a uC board for another $10-30 (even cheaper on ebay) and a quite good
>> OCXO for $10-30, also from ebay. A few wires, a bit of programming and
>> you have an GPSDO that beats the progrock. So, by buying the right stuff
>> you can stay below $30 and have something that will get you a long way
>> for experimenting.
>>
>> Just for the fun of it:
>>
>> http://www.ebay.com/itm/STM32F030F4P6-ARM-CORTEX-M0-Core-Mini-System-Development-Board-5V-3-3V-/371769616187?hash=item568f32273b:g:seAAAOSwXeJYCx63
[http://i.ebayimg.com/images/i/371769616187-0-1/s-l1000.jpg]<http://www.ebay.com/itm/STM32F030F4P6-ARM-CORTEX-M0-Core-Mini-System-Development-Board-5V-3-3V-/371769616187?hash=item568f32273b:g:seAAAOSwXeJYCx63>

STM32F030F4P6 ARM CORTEX-M0 Core Mini System Development Board 5V/3.3V | eBay<http://www.ebay.com/itm/STM32F030F4P6-ARM-CORTEX-M0-Core-Mini-System-Development-Board-5V-3-3V-/371769616187?hash=item568f32273b:g:seAAAOSwXeJYCx63>
www.ebay.com
This board is a STM32F030F4P6 Minimum System Board(Cortex-M0). The target MCU is STM32F030F4P6 that is provided by ST. It is a ARM 32-bit Cortex?. -M0 CPU, frequency up to 48 MHz, high-speed embedded memories. | eBay!



>>
>> $1.40
>> http://www.ebay.com/itm/MCP4725-I2C-DAC-Breakout-Development-Board-12Bit-Resolution-/401209928223?hash=item5d69f9aa1f:g:j5gAAOSw34FVH5b1
[http://i.ebayimg.com/images/i/401209928223-0-1/s-l1000.jpg]<http://www.ebay.com/itm/MCP4725-I2C-DAC-Breakout-Development-Board-12Bit-Resolution-/401209928223?hash=item5d69f9aa1f:g:j5gAAOSw34FVH5b1>

MCP4725 I2C DAC Breakout Development Board 12Bit Resolution | eBay<http://www.ebay.com/itm/MCP4725-I2C-DAC-Breakout-Development-Board-12Bit-Resolution-/401209928223?hash=item5d69f9aa1f:g:j5gAAOSw34FVH5b1>
www.ebay.com
This version of the CJMCU-MCP4725 Breakout fixes a few issues with the board including the IC footprint, the I2C pinout, changes the overall board dimensions to better fit your projects, and a few more minor tweaks. | eBay!



>>
>> $1
>> http://www.ebay.com/itm/Aircraft-Flight-Controller-w-Ublox-NEO-6M-GPS-Module-for-Arduino-APM2-/182318966076?hash=item2a730ea53c:g:QuoAAOSwOVpXc3K~
[http://i.ebayimg.com/images/i/182318966076-0-1/s-l1000.jpg]<http://www.ebay.com/itm/Aircraft-Flight-Controller-w-Ublox-NEO-6M-GPS-Module-for-Arduino-APM2-/182318966076?hash=item2a730ea53c:g:QuoAAOSwOVpXc3K~>

Aircraft Flight Controller /w Ublox NEO-6M GPS Module for Arduino APM2 | eBay<http://www.ebay.com/itm/Aircraft-Flight-Controller-w-Ublox-NEO-6M-GPS-Module-for-Arduino-APM2-/182318966076?hash=item2a730ea53c:g:QuoAAOSwOVpXc3K~>
www.ebay.com
1pcs Ublox NEO-6M GPS Module Aircraft Flight Controller For Arduino MWC IMU APM2. Compatible with various flight controller module. Module with ceramic active antenna. Module size:23 x 30mm. We can also provide customized design and manufacture services. | eBay!



>>
>> $5.04
>> http://www.ebay.com/itm/1-USED-ISOTEMP-OCXO-143-141-10-MHz-5V-SC-CUT-Square-Wave-Crystal-Oscillator-/331997554003?hash=item4d4c98a553:g:w~sAAOSwCGVX~g24
[http://i.ebayimg.com/images/i/331997554003-0-1/s-l1000.jpg]<http://www.ebay.com/itm/1-USED-ISOTEMP-OCXO-143-141-10-MHz-5V-SC-CUT-Square-Wave-Crystal-Oscillator-/331997554003?hash=item4d4c98a553:g:w~sAAOSwCGVX~g24>

1×USED ISOTEMP OCXO 143-141 10 MHz 5V SC-CUT Square Wave Crystal Oscillator | eBay<http://www.ebay.com/itm/1-USED-ISOTEMP-OCXO-143-141-10-MHz-5V-SC-CUT-Square-Wave-Crystal-Oscillator-/331997554003?hash=item4d4c98a553:g:w~sAAOSwCGVX~g24>
www.ebay.com
Conditiion: Used. I promise I can give you satisfying solution. It is good for you and for me! I try my best to select good products to you and service you sincerely. Rate (item arrived). | eBay!



>>
>> $16
>>
>> Total cost: ~$25 including shipping and all but the OCXO are new.
>> You will need programmer for the uC board, if you don't have that,
>> change
>> the uC board for an STM32F0DISCOVERY board:
>> http://eu.mouser.com/ProductDetail/STMicroelectronics/STM32F0DISCOVERY
[http://eu.mouser.com/images/stmicroelectronics/images/64824_fig2.jpg]<http://eu.mouser.com/ProductDetail/STMicroelectronics/STM32F0DISCOVERY>

STM32F0DISCOVERY STMicroelectronics | Mouser<http://eu.mouser.com/ProductDetail/STMicroelectronics/STM32F0DISCOVERY>
eu.mouser.com
STM32F0DISCOVERY STMicroelectronics Development Boards & Kits - ARM Discovery F0 Board 32-Bit ARM Cortex M0 datasheet, inventory & pricing.



>>
>> Of course, any "real" GPSDO will beat this one by orders of magnitude
>> in phase noise and stability, but they are also much less fun to
>> build :-)
>>
>>
>>             Attila Kinali
>
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