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Symmetricom X72 (and other rubidium oscillator) signal breakout boards
Posted by texaspyro on 07 Dec, 2017 21:00 -
The Symmetricom X72 is a very small rubidium oscillator. It outputs 10 MHz, 60 MHz, 1PPS, and has a programmable ACMOS level output signal. It is usually available for a decent price. The main problem with them is it requires an obsolete, rather unobtainium Molex connector to connect to it. Symmetricom did offer a small board that had an edge tab that could plug into the Molex connector and broke out the signals to a 0.1" dual row header.
A while back a bunch of the X72s with the connector board were available on Ebay, but it only broke out a few signals. Those available now don't seem to even have that board. Sooo.. what's a boy to do? Well, build a better mousetrap, of course.
I built a two board solution. The first (interface) board has the edge tab and breaks out all 26 pins of the Molex to a 0.1" header. It also has the 10 MHz impedance matching R-C network.
The second (Breakout) board connects to the the interface board and breaks out the signals to 5 BNC connectors and has a 5V regulator and MAX232A RS232 level converter and DE9 connector. The RS-232 connector can connect a selectable polarity RS-232 level 1PPS signal to pin 1 of the DE9, but most X72's output a 400 ns PPS pulse which might be too short to be useful unless stretched. You can also route either the DC input or 5V regulated to pin 9 of the DE9.
The regulator has enough capacity and the header has a place for 8 more pins in order to be able to work with a future interface board for the Symmetricom SA22.c rubidium.
Each board has a 2.1mm DC jack, but only use one of them (preferably the interface board one... it' has the shortest connection to the X72) The power caps are rated at 25V... should be OK to run up to 19V without changing them. I run mine at 12V.
I have just finished an interface board for the Spectratime SRO100 rubidium and will be doing one for the LPFRS. The SA22.c one is going to be a pain. It uses a 2mm pitch connector mounted in the middle of the baseplate where you want to mount the unit to a heatsink... not sure of the best way to handle that.
I have shipped the first X72 batch out to those on time-nuts. PM me if you need an X72 interface. Price (assembled) is $27 shipped in the US, $35 international.
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I got in the first cut of my Spectratime SRO100 adapters for the X72 BNC board from OSHPARK. They seem to work well... except I did the boards before the SRO100 came in and they don't invert the serial data lines (the SRO100 serial lines are inverted from what a normal UART outputs). I removed the MAX232A chip from the X72 board and jumpered across it to test the board.
I have the next rev off to DIRTYPCBs. They have the serial data inverters and also a place for an EFC pot (driven by the SRO100 Vref line) and a pair of EFC adjustment range limiting resistors. -
My boards arrived today and they work perfectly now that I have the USB serial adapter sorted out.. I was able to set the output frequency by successive tuning to 10.000 000 000 00Mhz using my GPSDO as a reference. I will be doing further testing when my Cesium Standard gets here after Christmas. This s a really nice, small, package for precision offline timing. It has a very clean output signal and is very flexible.
Thanks again.
Jerry -
It has a very clean output signal and is very flexible.
If you like your output signals a little on the raggedy side try enabling the ACMOS output at say 10 MHz. That does a bit of a number on the peaks of the sine wave 10 MHz output. -
I got in the first cut of my Spectratime SRO100 adapters for the X72 BNC board from OSHPARK. They seem to work well... except I did the boards before the SRO100 came in and they don't invert the serial data lines (the SRO100 serial lines are inverted from what a normal UART outputs). I removed the MAX232A chip from the X72 board and jumpered across it to test the board.
I have the next rev off to DIRTYPCBs. They have the serial data inverters and also a place for an EFC pot (driven by the SRO100 Vref line) and a pair of EFC adjustment range limiting resistors.
The update SRO100 adapter boards have shipped DHL Express. Should be here in 2-10 days.
I've been playing with the SRO100. When disciplined (using the default auto time constant setting) with an HP-5071A cesium beam oscillator the ADEV at 10,000 seconds is around 7E-14... not too shabby for a tiny Rb device.
When disciplined with a crappier 1PPS signal the SRO100 10 MHz output follows what the 1PPS input does fairly closely. For instance driving it with the 1PPS from a Thunderbolt, the Tbolt output 10 MHz and SRO100 10 Mhz were very similar... they were moving around 0.001 Hz over the heating system temperature swings. I need to try setting the time constant manually.
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I received the breakout boards a couple of days ago. Very nice job.
In the notes you say Lady Heather version >= 6.0 supports the X72. Where would I find this for Windows? -
I received the breakout boards a couple of days ago. Very nice job.
In the notes you say Lady Heather version >= 6.0 supports the X72. Where would I find this for Windows?
I hope to get the latest code to John Miles to build an official Windoze release in a week or two. If you run something Linuxy or can build the current 5.0 release on Windows I can send you the latest source code to build. -
I hope to get the latest code to John Miles to build an official Windoze release in a week or two. If you run something Linuxy or can build the current 5.0 release on Windows I can send you the latest source code to build.
I can wait.
How useful is Lady Heather with an X72? -
How useful is Lady Heather with an X72?
It can monitor and configure the device. It also has a routine to discipline the unit from the 1PPS input.
Later versions of the X72 firmware has a disciplining capability built in... but it seems to be rather picky about the PPS signal it will work with. I've had lots of problems getting it to work reliably with a lot of GPS receivers. -
One thing to keep in mind as mentioned above is configuration.
Not all X72s were created equal at the factory. Some have custom Firmware and Hardware options set, such as enabling 1PPS in/out. EFC enable is another one.
I have a Spectracom S200 NTP Server, with the X72 option. The EFC is definitely enabled on that one. The standalone X72 I have, does not have EFC, or 1PPS in/out options enabled. Obviously Hardware options would be, but I wonder if options set in Firmware are remembered on next power up? -
The standalone X72 I have, does not have EFC, or 1PPS in/out options enabled. Obviously Hardware options would be, but I wonder if options set in Firmware are remembered on next power up?
The pin functions/enables are set in the control reg. Have you tried changing them?
There is a "T" command for saving config stuff in EEPROM. What gets saved is not specified in the docs and may be firmware dependent. Also there is no way to read back the current settings of a lot of stuff you usually want to be able to read back. Lady Heather implements a "software eeprom" that saves the settings it knows about or changes to a file and restores them whenever Heather starts up.
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I got in the adapter boards for the Spectratime SRO100 / SRO75 rubidiums today. They fixed the serial port polarity issue of the first version and also added a place for an EFC adjustment pot. They seem to be working well.
I'm waiting for the LPFRS to arrive from China before I do an adapter for it. -
How would I order a X72 interface board assembled for $27.00?
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How would I order a X72 interface board assembled for $27.00?
PM sent... -
check your massage
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I did some looking at the best way to do an interface board to connect the BNC board to the Symmetricom SA22.c rubidium and think I have it worked out. PCB layout is in progress.
The SA22.c only outputs a 5V ACMOS 10 MHz square wave output. I'm looking into filter circuits to convert it to a decent-ish sine wave.
I now have an interface board available for the Spectratime SRO100 and SRO75 rubidium oscillators.
I am also going to do an interface board for the LPFRS (should also work with the LPRO-100, but that one has no serial port). That board will have a PICDIV chip to output a 1PPS signal.
Also, Lady Heather now talks to the SRO100, LPFRS, and the Oscilloquartz OSA-453x GPSDOs.
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I have the SA22.c interface board prototype laid out and off to OSHPARK. Should be here in a couple of weeks.
I'm shooting for a price of around $30-$35 for the two board set. The interface board is larger than the X72 board and has some pricey-ish parts on it. Also the assembler monkeys learned their lesson with the X72 version and have jacked up the price a bit.
I'm also looking at re-working the BNC board to add footprints for SMA connectors under the BNC footprint.
I'd like to get a feel for how many people are interested in the SA22 version...
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I have completed a layout for the signal adapter board to connect an LPFRS or LPRO compatible rubidium oscillator (or any general purpose Rb or OCXO) to my X72 BNC connector/RS232 board.
The LPFRS is a small rubidium oscillator. It is usually sold mounted on a heatsink with a small board that provides an LPRO compatible connector, except it replaces the lamp and xtal voltage monitoring pins with a serial interface.
My interface board can replace the LPFRS board or it can be connected via the LPRO connectors. It has support for an EFC voltage setting pot that provides 0-5V (or you can use the EFC input BNC on the connector board). It also has a PICDIV chip for generating a 1PPS output. When used with the LPRO or an oscillator that does not have a serial port (or you don''t want to use the LPFRS serial port) the board also has a place for a PICPET timestamping time interval counter chip.
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The Symmetricom X72 is a very small rubidium oscillator. It outputs 10 MHz, 60 MHz, 1PPS, and has a programmable ACMOS level output signal. It is usually available for a decent price. The main problem with them is it requires an obsolete, rather unobtainium Molex connector to connect to it. Symmetricom did offer a small board that had an edge tab that could plug into the Molex connector and broke out the signals to a 0.1" dual row header.
A while back a bunch of the X72s with the connector board were available on Ebay, but it only broke out a few signals. Those available now don't seem to even have that board. Sooo.. what's a boy to do? Well, build a better mousetrap, of course.
I built a two board solution. The first (interface) board has the edge tab and breaks out all 26 pins of the Molex to a 0.1" header. It also has the 10 MHz impedance matching R-C network.
The second (Breakout) board connects to the the interface board and breaks out the signals to 5 BNC connectors and has a 5V regulator and MAX232A RS232 level converter and DE9 connector. The RS-232 connector can connect a selectable polarity RS-232 level 1PPS signal to pin 1 of the DE9, but most X72's output a 400 ns PPS pulse which might be too short to be useful unless stretched. You can also route either the DC input or 5V regulated to pin 9 of the DE9.
The regulator has enough capacity and the header has a place for 8 more pins in order to be able to work with a future interface board for the Symmetricom SA22.c rubidium.
Each board has a 2.1mm DC jack, but only use one of them (preferably the interface board one... it' has the shortest connection to the X72) The power caps are rated at 25V... should be OK to run up to 19V without changing them. I run mine at 12V.
I have just finished an interface board for the Spectratime SRO100 rubidium and will be doing one for the LPFRS. The SA22.c one is going to be a pain. It uses a 2mm pitch connector mounted in the middle of the baseplate where you want to mount the unit to a heatsink... not sure of the best way to handle that.
I have shipped the first X72 batch out to those on time-nuts. PM me if you need an X72 interface. Price (assembled) is $27 shipped in the US, $35 international.
Still available, or not???
Thanks! -
Can I still order this board ?
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Hi; is this still available?
Regards
WT -
Don't think so, I asked 2 weeks ago, until now no answer.
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This seems to be a very hard question to answer. Waited over two years now without a simple yes, or no...
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I have made a few break out board.
I can sell it if any one needs.
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@nextwave I bought a couple of these from you and you said it would cost $25 to send from South Korea right now. That's unfortunate because they look pretty decent.
Bill