A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)

[lamaral]

I found some patents filed by Samsung that describes a system very similar to the UCCM. The numbers are US8116405B2 and US20090034672A1.
The one described on the patents even have an Ethernet PHY.

[wkb]

I built a 2nd GPSDO for /P use (something to do with sofar vague plans to experiment on the microwave ham bands).

This one is a lot more compact than my shack/lab unit: no distribution amplifier but instead a passive Minicircuits 1:2 splitter, no OrangePi to run LadyHeather but just a simple DB9 plug to connect to the laptop serial port etc.  The Samsung UCCM I mounted sort-of vibration isolated using thin FR4 PCB.

Wilko

[wkb]

Below the SMA sits a TNC connector for the GPS antenna by the way.

Both the TNC and BNC 10MHz connectors sit recessed "Neutrik style"

[Bad_Driver]

Nice job!

One question - may be there is an answer elsewhere in this topic - my Samsung works fine! My Symmetricom
runs ok as well, but I got it "naked" without OCXO. It runs with an external TRIMBLE 12V OCXO on an external board
with external PSU. But I'm going to consolidate it in a leaner setup. (The TRIMBLE doesn't fit on the board)

Which (double oven) OCXOs can be used on the Symmetricom board nowadays? It seems that prices for OCXOs
are exploding and the market is nearly empty. Can I ask for advice?

Thanks B.D.

[wkb]

Supply current for cold start of a Samsung UCCM.

Once you have a HPIB-equipped multimeter and an AR488 HPIB-serial converter (see https://eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/ ) you will use it for all sorts of things 

Side note: I am supply the UCCM 13.8V via a DC-DC converter that produces 5.5V.  This unit is destined for portable use using a 13.8V battery in ham microwave experiments. So some loss is to be expected in the DC DC converter.

Wilko

[bingo600]

Side note: I am supply the UCCM 13.8V via a DC-DC converter that produces 5.5V. 
Wilko

So this is the 13.8v current ?

[wkb]

Side note: I am supply the UCCM 13.8V via a DC-DC converter that produces 5.5V. 
Wilko

So this is the 13.8v current ?

Correct

[bingo600]

Side note: I am supply the UCCM 13.8V via a DC-DC converter that produces 5.5V.  This unit is destined for portable use using a 13.8V battery in ham microwave experiments. So some loss is to be expected in the DC DC converter.
Wilko

Can you tell more about the DC-DC converter you used ?
I have 2 Samsing UCCM's here , and i might want to run one of 13.8v like you
Thank you

/Bingo

[wkb]

Side note: I am supply the UCCM 13.8V via a DC-DC converter that produces 5.5V.  This unit is destined for portable use using a 13.8V battery in ham microwave experiments. So some loss is to be expected in the DC DC converter.
Wilko

Can you tell more about the DC-DC converter you used ?
I have 2 Samsing UCCM's here , and i might want to run one of 13.8v like you
Thank you

/Bingo

Nothing special, one of the supposedly 3A modules shown on the picture.

The Samsung UCCM has an onboard LDO regulator so I decided to not worry about the heresy of feeding a GPSDO from a SMPS

[Bad_Driver]

Hi Folks,

once again the question:

Which (other) double oven OCXOs fit into the SYMMETRICOM UCCM board? (that the SYMMETRICOM fits should be clear)

Thanks in advance!

[LukGasp]

Hello there!
I recently acquired a Symmetricom GPSDO out of AliExpress. It came without an OCXO but I managed to temporarily install a 5Vdc 10MHZ unit on it.
The problem being after typing POSSTATus no satellites to be found. It has been two hours since I switched it on.
The latest STATus is as follows:

UCCM-P > STATus

                 - UCCM Slot STATE -



1-1. #Now ACTIVE STATUS ---------------- [Alarm]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warm]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [GPS]
2-3. #Current Select Reference --------- [GPS 1PPS]
2-4. #Current Reference Status --------- [NOT SELECTED]
     #GPS STATUS ----------------------- [Unavailable]
     #Priority Level ------------------- [GPS > LINK]
     #ALARM STATUS
     #H/W FAIL ---------- [ LINK ]
3-1. PLL STATUS ------------------------ [Enable]
3-2. Current: PLL MODE ----------------- [OFFSET OBSERVATION MODE]
Command Complete
UCCM-P >

POSSTATus as follows:

1/6/1980 01:30:36
-----------------------------------------------------------------------------
 Position : LAT(N 34:44:0.000) LON(E 135:21:0.000) H(0.00 m MSL)
-----------------------------------------------------------------------------
 Geometry : PDOP(0.0) HDOP(0.0) VDOP(0.0)
-----------------------------------------------------------------------------
 Channel Status
   num of visible sats > 12
   num of sats tracked > 1
   ------ Receiver Channel State ------
     CH 0 >  SateID(3) TrackMode(code search) SigValue(0)
     CH 1 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 2 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 3 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 4 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 5 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 6 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 7 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 8 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 9 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 10 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 11 >  SateID(0) TrackMode(code search) SigValue(0)
-----------------------------------------------------------------------------
  Rcvr Status(1) :
-----------------------------------------------------------------------------
  Antenna Voltage: 4686 mV,  Antenna Current: 14 mA
-----------------------------------------------------------------------------
Command Complete
UCCM-P >

Could someone help me out, please?

73,

LukGasp

[cdev]

You likely need to give the GPSDO some information about the replacement OCXO you are using, to get it "close enough" to get a GPS lock.

Did they sell it to you without a OCXO?

I have a working unit that has the OCXO. Its working very well. I also have a standalone Bliley 10 Mhz OCXO with a square wave output. Many OCXOs use similar footprints. They are standardized parts.

[LukGasp]

cdev, thanks for your reply!

How can I give the GPSDO the information it requires about the replacement OCXO, please?

I have bought an Oscilloquartz 10Mhz sine 12Vdc double oven OCXO 8663-XS that some Ali express tried before, but it is on the way home as I write this post. That 8663-XS has the same footprint as the original one.

The unit was sold without an OCXO to me.

I found out that the smaller footprint, on the pcb, will not properly feed +5Vdc to a 5Vdc square OCXO.

My unit came with the Furuno GT-8031F GPS module and I cannot receive any satellites whatsoever, even after it has been turned on for more than 3,5 hours in a row. Any thoughts on that?

Cheers,

LukGasp

[ZigmundRat]

To my knowledge these do not run the GPS or CPU clock from the OCXO. (It could, I just don’t know, and I don’t recall seeing it mentioned.) What’s interesting to me is that it reports 12 visible sats and tracking only one. So the GPS receiver is at least partially working. Did you notice the latitude/longitude puts you in Japan? (Your profile flag implies Brazil I think.)

You could try entering your current location with: GPS:POSition N or S,<deg>,<min>,<sec>,E or W,<deg>,<min>,<sec>,<height> - an approximate location is fine. Setting the location this way can make a big difference in startup.

You make no mention of the antenna, whether it’s confirmed to work with other GPS with 5v antenna feed, or the antenna location. The Furuno receiver is not known for it’s high sensitivity.

[LukGasp]

ZigmundRat,

I entered the new location data according to your explanation, though it did not work. It shows  Position : LAT( LON( H(0.00 m MSL)

It has been two hours since I switched it on. The antenna is a regular Active +5Vdc one. It has been tested before and the location can be received by other GPS receivers with the same antenna.

Any other issues that may help me sort that problem out, please?

On start up it shows the following:
Symmetricom Boot Code ver. 1.01.01

Press Enter to go to boot
Image1: [1.0.0.2] [454535 bytes] [valid checksum:0x20AFA24] [timestamp:3]
Image2: [1.0.0.1] [454535 bytes] [valid checksum:0x2142B89] [timestamp:2]


As of now it shows the following POSTATus:

UCCM-P > POSSTATus
-----------------------------------------------------------------------------
1/6/1980 00:53:01
-----------------------------------------------------------------------------
 Position : LAT( LON( H(0.00 m MSL)
-----------------------------------------------------------------------------
 Geometry : PDOP(0.0) HDOP(0.0) VDOP(0.0)
-----------------------------------------------------------------------------
 Channel Status
   num of visible sats > 0
   num of sats tracked > 0
   ------ Receiver Channel State ------
     CH 0 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 1 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 2 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 3 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 4 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 5 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 6 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 7 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 8 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 9 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 10 >  SateID(0) TrackMode(code search) SigValue(0)
     CH 11 >  SateID(0) TrackMode(code search) SigValue(0)
-----------------------------------------------------------------------------
  Rcvr Status(0) :
-----------------------------------------------------------------------------
  Antenna Voltage: 4598 mV,  Antenna Current: 14 mA

STATus as follows:

UCCM-P > STATus

                 - UCCM Slot STATE -



1-1. #Now ACTIVE STATUS ---------------- [Alarm]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warmup]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [GPS]
2-3. #Current Select Reference --------- [GPS 1PPS]
2-4. #Current Reference Status --------- [NOT SELECTED]
     #GPS STATUS ----------------------- [Unavailable]
     #Priority Level ------------------- [GPS > LINK]
     #ALARM STATUS
     #H/W FAIL ---------- [ LINK ]
3-1. PLL STATUS ------------------------ [Enable]
3-2. Current: PLL MODE ----------------- [OFFSET OBSERVATION MODE]
Command Complete

[tkamiya]

Be careful with those little DC/DC converter boards!  Of course not all of them are bad, but I have a personal experience with one that went rogue.  I was experimenting with ferrite beads on output side.  Suddenly, it went into violent oscillation and output went to 37V.  Also, output is pretty dirty - full of AC components. 

Name brand ones, TDK/Nemic Ramda on high end and MeanWell on lower end are pretty reasonably priced.  Digikey has lots of them.

[ZigmundRat]

Ok on the power on time, antenna, etc. It might be more appropriate to try using “gps:INITial:POSition” , same syntax. That should set the position assumed at startup before the survey happens. See how that works - but given that you weren’t able to get back to where you had visible satellites, I’m concerned that the GPS receiver has issues. I can’t help but wonder if that’s not why the OCXO was harvested. (Then again, maybe not… It’s always been a bit of a gamble with these units.)

Many have received damaged boards - Have you checked yours for broken/missing parts against the high res photos posted earlier in this thread? It’s a bit of a tedious process but necessary. I had to repair one of my units by using those photos. It’s also possible to have invisible damage of course.

One thing I didn’t see mentioned is the power supply you are using. What voltage are you feeding it and where?

[LukGasp]

ZigmundRat,

I have been running +5Vdc at 900mA on a 0-30Vdc 0-5Amps switched power supply.

Any other hints you may recall?

Thanks,

LukGasp

[thinkfat]

I'd try a system factory reset next. There's likely an old almanac stored in the GPS and it is looking for all the wrong satellites. The command is certainly somewhere in this thread.

[ZigmundRat]

Power supply seems close enough, but you might want to run it up to about 5.5v. I don’t think that will help your problem though. The GPS position commands were just to get it to get the initial fix sooner, hoping that you would then see satellites and start tracking.

Bottom line is that if you have a known good antenna and proper power, and in a couple hours it doesn’t find a location and start self survey, it’s broken. AFAIK there’s no software fix for this situation. You could always try resetting to defaults though. It can’t hurt.

That’s all I’ve got - sorry.

[LukGasp]

On my way to fix this GPSDO, I have noticed that it has an alarm:

Alarms:  [0200] 0.5Hz Internal Reference

Any ideas on how to fix that, please?

Thanks in adavnce!

[PA0PBZ]

On my way to fix this GPSDO, I have noticed that it has an alarm:

Alarms:  [0200] 0.5Hz Internal Reference

Any ideas on how to fix that, please?

This may help: https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg967071/#msg967071

[LukGasp]

I would like to thank all of you who helped getting my Symmetricon GPSDO fixed.
As I bought the unit without an OCXO, I investigated on Ali Express someone who had bought the same unit, that had installed an OCXO and got it working flawlessly.
I found one person who bought the Oscilloquartz 8663-XS 12V sinewave which fits perfectly on the PCB.
Yesterday afternoon I decided to test the OCXO and it worked flawlessly. A bit after that, my good friend Irineu and I soldered it onto the PCB, got rid of the alarm but couldn't get any satellites...until I took the antenna outside on the top of a metal can. Bingo! It worked, but it took almost 4 (four) hours to get the survey done and get a fix. The Furuno GPS module is quite deaf and needs a good antenna with a clear sky view.

I believe I must get a good 36dB gain Rosenberger GPS antenna and connect it to the GPSDO using a low loss cable.

Now my question is: will it go the same survey thing everytime I power the GPSDO on???


Thanks once again for your valuable assistance! Do not hesitate to contact me in case you need more info regarding the Oscilloquartz 8663-XS 12V sinewave 12V OCXO.

[SHF]

Hi,
With my GPSDO with Furuno GPS module, it takes a maximum of 2 minutes after switching on until the GPS-FIX is up. As an antenna I use one from Ebay
https://www.ebay.de/itm/124013801979?hash=item1cdfcc71fb:g:BZ4AAOSwCAdd-Fwn

[LukGasp]

I powered my unit earlier today, once again, with a regular GPS antenna, one of those small black ones that most any regular guy such as me has at home...Spent two hours waiting for the survey to start but, only one satellite was tracked...and that is not enough...at least 4 satellites being tracked are required...
The Furuno asks for a better antenna....and you just sent some good news from Germany. Thank you! Looking forward to receiving the new GPS antenna.