Economical option for precision frequency reference?

[SoundTech-LG]

yes... cool, probably not worthy of such a fine instrument, but I'll be trying my best...

No option cards installed, and it has the standard OCXO, so nothing extremely exciting, but at least it doesn't have the downgrade TCXO  . I was thinking of doing a teardown with photos, or video. Spectracom claims it is impossible to upgrade the reference oscillator after manufacturing, but maybe they are not counting on an EEVblogger investigating that possibility. I noticed the unit weight increases by roughly a half pound with the high stability Rb Osc. installed. That does not sound like a surface mount device! Should be in my hands early next week some time.

[Vgkid]

When i first was getting into this...
I saw a spectracom 9183(i think right model) gps freq std. Reading the manual i determined to have the rb option. I bid,  put a max bid of 205. And lost. Another one appeared bid first, max bid of 343... lost again. The only person bidding against me was the same person. I was upset.

[TheSteve]

Finally received my Trimble unit a few days ago. It is the same or a very similar unit used in the BG7TBL trimble units. I have it mounted in a box and it has been running for a few days now. So far I have no complaints. While I have no primary source to compare it to the jitter between it and my Nortel has been under 30ns over a 24 hour period. My unit has the 63090 OCXO in it. The part # on the board itself is 57964-15. The board appears to use an Xemics 3330R GPS RF front end IC which feeds I/Q outputs to the processor for decoding.

The output from the command "*IDN?" is:

TRIMBLE,57964-15,86972377,V3.0.0.11-01

If you have one of these units or the equivalent BG7TBL unit you can force a site survey with the command "SYSTem:PRESet"
The board stores the last survey location and maintains it without power. However as motocoder mentioned earlier in this thread it does not store the elevation mask setting. At power on it always defaults to 5 degrees. If you're performing a site survey I'd set it to 10 to 20 degrees.
The default serial comm is 57600,8,N,1

You can enable once per second time packets to be output via the serial port if needed. It has two dual color LEDs on the bottom of the board that I moved to the front of my enclosure. I didn't want to install 4 LEDs and didn't have any dual color common anode LEDs so I cheated and cut the tips off some 5 MM opaque LEDs and then used CA(glue) to attach the original SMD LEDs to the tips of the 5MM LEDs - it is working great and they look like regular 5MM dual color LEDs in use.

The board requires 6 volts @ 1.8 amps during warmup and 0.85 amps after it is warm. It is a possible cheap option for people if they already have an antenna/power/box etc and like building stuff. I got mine for 48 USD shipped off ebay but the price has since gone up quite a bit. I do see there is a Symmetricom version of the same board for for 48 USD shipped though which is likely a potential good option.
If you want a complete solution it would be tough to beat the regular BG7TBL packages offered on ebay.

I also came across a working Cesium reference for 1K today - sadly it is out of my budget for a fun toy.

Attached a few pics of the unit. I've since ordered a black enclosure so I may swap the top and bottom halves so its totally black when it comes in next week.

[Macbeth]

I do see there is a Symmetricom version of the same board for for 48 USD shipped though which is likely a potential good option.
If you want a complete solution it would be tough to beat the regular BG7TBL packages offered on ebay.

I believe this is what you refer to? I've just bought one anyway. Time to dip my toe in the time-nuts water. Perhaps I should buy some RF connectors while I wait for it to arrive. What are they? SMA?

[TheSteve]

I do see there is a Symmetricom version of the same board for for 48 USD shipped though which is likely a potential good option.
If you want a complete solution it would be tough to beat the regular BG7TBL packages offered on ebay.

I believe this is what you refer to? I've just bought one anyway. Time to dip my toe in the time-nuts water. Perhaps I should buy some RF connectors while I wait for it to arrive. What are they? SMA?

Yep, that is the one. The mating connectors for the jacks on the board are MCX - this is the cable I used with the BNC connectors - http://www.ebay.com/itm/281313869844

[motocoder]

I have decided to sell the Lucent, BG7TBL Trimble, and BG7TBL units that I bought to do the test/evaluation.

 The two BG7TBL units come with the antenna and power supply that the eBay seller ships with them.

The Trimble unit has some ventilation holes in the case. I added these because its oven runs quite hot, and I was concerned about longevity of the other components in the case.

The Lucent comes with a high quality medical grade power supply to which I have afixed the DB9 power connectors with the appropriate latches. It also comes with a high quality, FTDI-based RS-422 to USB adapter and a DB9 adapter cable. I'll throw in a TNC to N patch cable as well.

PM me if intetested.

[SoundTech-LG]

I know there are curious types around here, so I wanted to do this minor tear-down, actually, more a description of the interior of the Spectracom SecureSync unit. There is not really much to disassemble.

 I also wanted to test it right away for 100% functionality, and no error conditions. So it has been powered on for a little more than a week now,
 and has begun to settle down a bit. It does seem quite sensitive to room temperature change. I live in a canyon, so reception is poor here.
 Removing no less than 20 screws just to pop the cover while powered up to try to prevent any fluctuations in performance,
 but taking the cover off lowered the temperature severely. I started wondering about the thermal environment it had been designed for.
I think in a very warm rack space. The unit has 6 option slots on the rear panel, but each are perforated with plenty of holes.
So if all 6 option slots are filled with modules, the holes go away, and now added heat from the modules, all keeping it quite toasty inside.
 It does have a fan, but according to the instructions you may never hear it cycle on, except briefly at power on. I decided covering the option
 blanks with tape to isolate it from the outside air was a good idea. Fan still does not cycle on. Temp slightly higher now, and less fluctuation.

The GPS radio is a Trimble resolution T. The standard 10 mHz OCXO is a Russian made Morion MV-197. It has a Western Digital SSD of 1 GB.
 A small computer on board, an SOM-4455 by Advantek, featuring an AMD Geode LX 800 CPU, AMD CS5536 chipset, and 1GB of DDR-400 RAM.
The backup battery is a huge coin cell BR3032.  You can see the area of the board for the optional DC power, no fuse installed, and J33 not connected,
2 rather large inductors sitting there as well.

The Rubidium option jacks are there, no info about what that is. Even if you could ID it, Firmware for it would need to be installed.
According to Spectracom there are no upgrades after production. It appears to be a late 2012 production unit. The SSD is dated 9/5/12,
 the Morion MV-197 dated 12/28, which is the 28th week of 2012. All in all a pretty interesting, and quite sophisticated unit.

Here's a few photos of the interior, front, and rear. and some screen shots of interest.

[SoundTech-LG]

more photos

[SoundTech-LG]

more...

[SoundTech-LG]

more

[SoundTech-LG]

more

[SoundTech-LG]

a few more

[SoundTech-LG]

done

[Vgkid]

Thanks for the teardown, I was wondering when you would post more pics...

[SoundTech-LG]

Hi,

Yes, testing came first.

 It appears possible to upgrade to the Morion Ultra LN OCXO double oven MV-209. Same footprint, just a tad taller.I doubt it would require a FW change.  I have to check the PS voltage, and whether Sine or CMOS output.

http://www.morion.com.ru/catalog_pdf/26_MV209.pdf

[TheSteve]

I have been touring ebay for a distribution amplifier after reading that several people have used video amplifiers for the job. Decided on a Link Electronics video distribution amplifier that was 19.95 plus shipping. Opened it up, removed the eight 75 ohm output resistors and installed eight 49.9 ohm resistors. Set it to single ended mode, added an output terminator and then set the output level to 0 dBm into 50 ohms. The output looks good on my scope and spectrum analyzer. It will now be feeding 10 MHz to all of my devices. I liked this model because it had 8 outputs which should take me a long time to use and it uses less then 4 watts of power. Combined with the Trimble GPSDO the pair use under 10 watts which I think is fine to leave running 24/7 in the lab.

So anyone looking to run 10 MHz to a bunch of devices, check out the video amps on ebay.

EDIT:

After playing with this amp for a while I noticed I was able to see spurs above and below 10 MHz when using a very narrow RBW on my spectrum analyzer. Turns out they were 120 Hz above and below 10 MHz. A quick look at the amp explains while - it uses a full wave bridge rectifier, filter caps and no regulators. Internally it runs at plus and minus 10 volts. I cut some traces and wired in a 7805 and a 7905 with some caps. Before I did that I verified with an external supply that it seemed to run just fine at plus and minus 5 volts. The spurs are now gone and the output is cleaner. I may still get a 7808 and a 7908 next time I order from Digikey and wire them in to give a little more headroom. Turning the output all the way up though shows no clipping as it is. I believe the video input levels may be higher then the 1.5 vpp my GPSDO outputs.

[Macbeth]

Well, I got my Symmetricom module and some of those MCX-BNC leads

Unfortunately the MCX socket for the GPS antenna appears to have been ripped from the board, and wasn't even to be found loose in the mail package. I will have to source one, but a bit of a PITA as it's a surface mount component. Also, there are two push buttons, MACT and RST. The MACT ones cap fell off and the spring contact vanished (if it was even there). Now those faults aren't so bad, but powering it up the DC/DC converter is ringing and no 5V, so no LED's or anything

I've powered up using the spare BT pin on the DBG connector using a 5V and everything kicks into life, but of course the oven isn't warming up

I've asked the seller for a return. He's initially responded with me finding the MCX connector locally and he will refund me that. Ok, but it was sold as used cosmetic wear and tear, fully functioning... If I didn't have a hot air station then I would be buggered.

So I'll carry on investigating this while I wait for his response and either return it for full refund or get a decent discount.

[TheSteve]

Well that sucks. Even if you do get it working they should probably give you a full refund as its not quite a simple fix at this point. Would you be able to provide some pics of the board? The ones on ebay are pretty crappy.

[Macbeth]

Well, one I took to send to the seller. Note the missing MCX and the dodgy looking MACT button. When I upturned the board the top fell off and the contact spring vanished 



The seller is telling me I could solder the socket with a normal iron "as its only 4 pins". I asked him how he would solder the 5th centre pin with an iron? hahaha. It's besides the point as it was advertised as working. Basically I've asked for a full refund or for him to send me a replacement. I've offered to return this at his cost of tracked delivery (£47), I somehow don't think he will want it back.

Nevertheless, I persisted with trying to get somewhere with it in the meantime. I found any voltage I applied to the 10A fuse (3.3V - 12V) would clamp my Rigol PSU at something around 3.3-4V. I had current limiting set to 2A but it would peak at about 1.6A. Ringing noise coming from the DC/DC converter and no indicator LEDs. The OCXO would get pretty toasty. There are various test points on board, 1.2V, 3.3V good, 5V was bad - less than 4V. A PWR test point going to the OCXO was around 8-9V even with only 5-6V supply. Another test point VREF is in the 4-5V range.

I found that not using the main power but the BT (battery?) connection on the 4 pin DBG (rx/tx) header with 5V flicked the board into life. Combining 2 supplies, 5V at BT and 6V for power in the ringing would stop when the OCXO got really hot and then would stop heating as the current dropped from 1.5A to 300mA or so. I can connect using serial OK and plenty of commands to play with. Looking at the diagnostic log this device was previously installed somewhere north of Tokyo back in 2014

When the DC/DC converter settled down I found I could remove the 5V BT supply and it would remain running. So I've been playing with the serial commands for now.

[Macbeth]

Some interesting serial logs:

Powered on and help command

Code: [Select]


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]

Loading Image1
UCCM-P > ?
*IDN?
ALARm:HARDware?
ALARm:OPERation?
DIAGnostic:OUTPut ON|OFF
OUTPut:ACTive:ENABle
OUTPut:ACTive:DISable
OUTPut:ACTive:HOLDover:DURation:THReshold <seconds>
OUTPut:ACTive:HOLDover:DURation:THReshold?
OUTPut:INACTive
OUTPut:INACTive?
OUTPut:STATe?
SYNChronization:HOLDover:DURation:STATus:THReshold <seconds>
SYSTem:PRESet
SYNChronization:TFOMerit?
LED:GPSLock?
SYNChronization:FFOMerit?
GPS:POSition N or S,<deg>,<min>,<sec>,E or W,<deg>,<min>,<sec>,<height>
GPS:POSition?
GPS:POSition:HOLD:LAST?
GPS:REFerence:ADELay <numeric value>
GPS:REFerence:ADELay?
GPS:SATellite:TRACking:COUNt?
GPS:SATellite:TRACking?
DIAGnostic:ROSCillator:EFControl:RELative?
SYNChronization:TINTerval?
DIAGnostic:LOG:READ:ALL?
DIAGnostic:LOG:CLEar
SYSTem:PON
OUTPut:MODE?
SYSTem:STATus?
SYSTem:COMMunication:SERial1:BAUD 9600|19200|38400|57600
SYSTem:COMMunication:SERial1:BAUD?
SYSTem:COMMunication:SERial1:PRESet
SYSTem:COMMunication:SERial2:BAUD 9600|19200|38400|57600
SYSTem:COMMunication:SERial2:BAUD?
SYSTem:COMMunication:SERial2:PRESet
OUTPut:STANby:THReshold <seconds>
changeSN
SYNChronization:REFerence:ENABLE LINK|GPS
SYNChronization:REFerence:DISABLE LINK|GPS
SYNChronization:REFerence:ENABLE?
STATus
POSSTATus
TOD EN|DI
TIME:STRing?
REFerence:TYPE GPS|LINK
REFerence:TYPE?
PULLINRANGE 0|1|2|...|254|255
PULLINRNAGE?
DIAGnostic:LOOP?
DIAGnostic:ROSCillator:EFControl:DATA GPS|<value>
DIAGnostic:ROSCillator:EFControl:DATA?
OUTPut:TP:SELection PP1S|PP2S
OUTPut:TP:SELection?
GPSystem:SATellite:TRACking:EMANgle <degrees>
GPSystem:SATellite:TRACking:EMANgle?
DIAGnostic:TCODe:STATus:AMASk
DIAGnostic:TCODe:STATus:OMASk
DIAGnostic:TCODe:ERRor:AMASk
DIAGnostic:TCODe:ERRor:OMASk
DIAGnostic:HOLDover:DELay
DIAGnostic:HOLDover:DELay?
GPS:SATellite:TRACking:IGNore <PRN>, ...,<PRN>
GPS:SATellite:TRACking:IGNore?
GPS:SATellite:TRACking:INCLude <PRN>, ...,<PRN>
GPS:SATellite:TRACking:INCLude?
GPS:SATellite:TRACking:<select>:ALL
Command Complete
UCCM-P >

The STATUS command

Code: [Select]


UCCM-P > status

                 - UCCM Slot STATE -



1-1. #Now ACTIVE STATUS ---------------- [OCXO Warm]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warmup]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [LINK]
2-3. #Current Select Reference --------- [LINK0]
2-4. #Current Reference Status --------- [NOT SELECTED]
     #GPS STATUS ----------------------- [Unavailable]
     #Priority Level ------------------- [LINK > GPS]
     #ALARM STATUS
     #H/W FAIL ---------- [ LINK ]
     #OPERATION ALARM --- [ Antenna ]
3-1. PLL STATUS ------------------------ [Enable]
3-2. Current: PLL MODE ----------------- [OFFSET OBSERVATION MODE]
Command Complete
UCCM-P >

POSSTATUS

Code: [Select]

UCCM-P > posstatus
-----------------------------------------------------------------------------
1/6/1980 00:07:58
-----------------------------------------------------------------------------
 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 > 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(1) :
-----------------------------------------------------------------------------
  Antenna Voltage: 6255 mV,  Antenna Current: 0 mA
-----------------------------------------------------------------------------
Command Complete
UCCM-P >

I note the Antenna Voltage appears to track my supply voltage (6.5V in this case). This is a bit concerning as my GPS Antenna is only 3.3-5V. I have found powering the board up with less than 5.5 volts results in an error in the log regarding insufficient current for the OCXO. I have measured the reported voltage directly at the (stripped) antenna connection and it is correct.

Finally the SYST:STATUS? command

Code: [Select]


UCCM-P > syst:status?
-------------------------------------------------------------------------------
090-03861-03   serial number W5609120082   firmware ver 1.0.0.2-01     LINK mode
-------------------------------------------------------------------------------
Reference Status __________________________   Reference Outputs _______________
   Ref 8KHz 0: [LOS]
                                              TFOM     9             FFOM     3
                                              UCCM-P Status[OCXO WARM]

>> GPS: [no ref]
......................................................... [ GPS 1PPS Invalid ]
Tracking: 0 ____   Not Tracking: 0 ________   Time ____________________________
                                              GPS      00:20:17 [?] 06 JAN 1980
                                              GPS      Invalid: not tracking
                                              ANT DLY  +0.000E+00
                                              Position ________________________
                                              MODE     Survey:      0% complete
                                                       Suspended: track <4 sats
                                              INIT LAT N  34:44:00.000
                                              INIT LON E 135:21:00.000
                                              INIT HGT           +0.00 m  (MSL)




ELEV MASK  5 deg
-------------------------------------------------------------------------------

Command Complete
UCCM-P >

Now for the provenance of this thing. Obtained from Hong Kong, the system status INIT LAT and LON show somewhere between KOBE and OSAKA in Japan while the data recorded in the diagnostic logs (now overwritten - 500 line limit) show 2 site surveys in 2013 and 2014 some place called KOSHIGAYA north of TOKYO 

[f1rmb]

Hi,

Some interesting serial logs:

...

I'm pretty interested with this board. Did you made some progress ?

[Macbeth]

Yes. I've asked the seller to send me a new one. He wanted me to send this one back, so I asked him to arrange his own courier or go through the cheapest tracked royal mail options available to be. Obviously he didn't want that. He eventually settled for sending me another one out. We will see.

While sorting that out I found an MCX socket on an old junk board and swapped it over using hot air so I finally got to see some satellites. I'm using one of those cheap 3.3-5V "GPS Mouse" antennas stuck to a drainpipe outside my window.

However, the DC/DC converter was still troublesome and now the board would power up with only one supply but the oven wouldn't heat up and I couldn't get my 10MHz output.

It turns out the OCXO runs at 12V generated from a single 5V supply by a TI boost converter module (which is now kaput). I removed the module and powered up from with 12V directly to the OCXO and 5V supply and now everything is working.

I was considering making a dual supply for it but I've found the exact drop in replacement boost converter on AliExpress for around £3   

[f1rmb]

Hi,

Yes. I've asked the seller to send me a new one. He wanted me to send this one back, so I asked him to arrange his own courier or go through the cheapest tracked royal mail options available to be. Obviously he didn't want that. He eventually settled for sending me another one out. We will see.

While sorting that out I found an MCX socket on an old junk board and swapped it over using hot air so I finally got to see some satellites.

However, the DC/DC converter was still troublesome and now the board would power up with only one supply but the oven wouldn't heat up and I couldn't get my 10MHz output.

It turns out the OCXO runs at 12V generated from a single 5V supply by a TI boost converter module (which is now kaput). I removed the module and powered up from with 12V directly to the OCXO and 5V supply and now everything is working.

I was considering making a dual supply for it but I've found the exact drop in replacement boost converter on AliExpress for around £3 

Great to read that. I guess I'll click the button ;-)

Did you connect the power supply (on the first step, before DC/DC troubles) like on the Trimble:
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-/181777773438

Also, do you have some documentation for this board (tried a quick google search without real success until now).

Cheers.
---
Daniel

[Macbeth]

Great to read that. I guess I'll click the button ;-)

Oh yes, hopefully you won't have any trouble. They are sold as working after all. But it's well worth it even if you have the hassle I had.

Did you connect the power supply (on the first step, before DC/DC troubles) like on the Trimble:
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-/181777773438

Yes. I started at 5V at the fuse and current limiting going up in steps to 12V, also down to 3.3V. I just had bad switching noise and the input circuit clamping my PSU voltage really low. Even with 12V it never got above 4V at the fuse. Boost converter eventually totally failed. (Not at 12V I might add - I had it running at 5.5-6V all this time to supply enough current to prevent reported OCXO failure, but it should really run at 5V alone)

Also, do you have some documentation for this board (tried a quick google search without real success until now).

Cheers.
---
Daniel

I'm looking but can't find anything specific. It does appear this board is a direct replacement for the Trimble though.

[f1rmb]

Great to read that. I guess I'll click the button ;-)

Oh yes, hopefully you won't have any trouble. They are sold as working after all. But it's well worth it even if you have the hassle I had.

Did you connect the power supply (on the first step, before DC/DC troubles) like on the Trimble:
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-/181777773438

Yes. I started at 5V at the fuse and current limiting going up in steps to 12V, also down to 3.3V. I just had bad switching noise and the input circuit clamping my PSU voltage really low. Even with 12V it never got above 4V at the fuse. Boost converter eventually totally failed. (Not at 12V I might add - I had it running at 5.5-6V all this time to supply enough current to prevent reported OCXO failure, but it should really run at 5V alone)

Also, do you have some documentation for this board (tried a quick google search without real success until now).

Cheers.
---
Daniel

I'm looking but can't find anything specific. It does appear this board is a direct replacement for the Trimble though.

Okay, many thanks for all these informations, I guess I'll order one board later today ;-)

EDIT: Ordered :-)

Cheers.
---
Daniel