Author Topic: Economical option for precision frequency reference?  (Read 155268 times)

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Offline TSL

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Offline usagi

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Re: Economical option for precision frequency reference?
« Reply #176 on: August 04, 2015, 06:30:51 am »
i have a bg7tbl huawei (oscilloquartz star 4), and i'm waiting for delivery of a bg7tbl trimble.

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #177 on: August 04, 2015, 06:23:47 pm »
i have a bg7tbl huawei (oscilloquartz star 4), and i'm waiting for delivery of a bg7tbl trimble.

Excellent. Looking forward to some comparisons.
 

Offline EV

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Re: Economical option for precision frequency reference?
« Reply #178 on: August 05, 2015, 11:28:08 am »
I'm assuming most of these posts are referring to the

LUCENT/SYMMETRICOM/HP Z3810AS, KS24361 L101 REF0 / L102 REF1, GPSDO TIMING SYSTEM

This REF0 unit has no GPS antenna connector. However it has "NO GPS" led. Can it be used as GPS reference separately without REF1 unit? Are there any instructions or manuals for these?
 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #179 on: August 05, 2015, 03:00:49 pm »
I'm assuming most of these posts are referring to the

LUCENT/SYMMETRICOM/HP Z3810AS, KS24361 L101 REF0 / L102 REF1, GPSDO TIMING SYSTEM

This REF0 unit has no GPS antenna connector. However it has "NO GPS" led. Can it be used as GPS reference separately without REF1 unit? Are there any instructions or manuals for these?

There was some discussion about this on the time-nuts mailing list. There was speculation that an external GPS could be hooked up and providing only the 1PPS signal to REF0, to allow a 21st century GPS chip to work with it and avoid the crappy insensitive chip that's in there now. However, I read every single message on time-nuts about this unit, and no one ever reported back as having even tried this.

AFAIK, there is no manual publicly available for these units. They were created as a drop-in replacement for an earlier unit, the KS-24019, and it is similar to a later unit, the Z3805A, for which I believe there is some documentation.
 

Offline usagi

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Re: Economical option for precision frequency reference?
« Reply #180 on: August 05, 2015, 10:10:27 pm »
There was some discussion about this on the time-nuts mailing list. There was speculation that an external GPS could be hooked up and providing only the 1PPS signal to REF0, to allow a 21st century GPS chip to work with it and avoid the crappy insensitive chip that's in there now. However, I read every single message on time-nuts about this unit, and no one ever reported back as having even tried this.

why bother, just get a bg7tbl oscilloquartz or bg7tbl trimble and be done with it.

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #181 on: August 05, 2015, 11:35:14 pm »
There was some discussion about this on the time-nuts mailing list. There was speculation that an external GPS could be hooked up and providing only the 1PPS signal to REF0, to allow a 21st century GPS chip to work with it and avoid the crappy insensitive chip that's in there now. However, I read every single message on time-nuts about this unit, and no one ever reported back as having even tried this.

why bother, just get a bg7tbl oscilloquartz or bg7tbl trimble and be done with it.

Yes, I agree. Just answering his question :)
 

Offline dadler

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Re: Economical option for precision frequency reference?
« Reply #182 on: August 06, 2015, 12:51:14 am »
So, I have some information about the RFTG units.

I've shared my personal directory here:

https://www.dropbox.com/sh/osgb29wvgnxag4v/AABzYRcHALPExnaa6hU7MLeua?dl=0

There is some software and an RFTG user manual from 1996. You guys might already have this stuff, but just thought I'd share just in case.
 

Online Vgkid

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Re: Economical option for precision frequency reference?
« Reply #183 on: August 06, 2015, 03:22:38 am »
I have a rftgm-II at home if anyone wants a teardown.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline EV

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Re: Economical option for precision frequency reference?
« Reply #184 on: August 06, 2015, 05:39:33 am »
Thanks for the info to motocoder and dadler!
 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #185 on: August 06, 2015, 05:49:27 am »
So, I have some information about the RFTG units.

I've shared my personal directory here:

https://www.dropbox.com/sh/osgb29wvgnxag4v/AABzYRcHALPExnaa6hU7MLeua?dl=0

There is some software and an RFTG user manual from 1996. You guys might already have this stuff, but just thought I'd share just in case.

So this is the manual for the older unit that the KS-24361 is patterned on, right?

For anyone thinking of downloading - the software does not run on recent versions of Windows.
 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #186 on: August 06, 2015, 06:05:13 am »
So I posted in the other thread, but forgot to post here that I obtained one of the BG7TBL 2015-07-17 "Trimble" units. This is basically a board NOT designed by BG7TBL, grafted onto a board of his design that provides connectivity to front-panel LEDs, DB9 RS-232 connector, power and RF connectors. My unit is all sealed up in an aluminum box, although I am a bit concerned about it overheating and may pull it out (the box doesn't feel hot at all, so maybe OK). It came with a puck antenna and power supply. Notably the antenna is labelled 3.3V, but the "documentation" that came with this unit clearly says it uses 5V antennas.

If the antenna is placed outside (my "lab" is apparently a GPS dead zone - only the most sensitive of GPS chips will lock up indoors there), it locks up within just a few minutes. The box puts out a very nice and clean sine wave. I don't have the ability to measure phase noise on it, so can't comment about how clean it is. If I hook it up to my scope, and trigger on the signal from the Lucent, I can see a very consistent and repeatable drift in phase between the two references of about 27ns. I need a third unit of some type to see what is responsible for this phase drift.

I will have to fashion an adapter cable to hook up RS-232 and see what can be done with that. The software that came with the unit will not run on my machine; it just errors out looking for some ancient VB6 OCX component (MSCOMM32.OCX).

Pros
  • Reasonably priced
  • Nice 10MHz sine wave output
  • Quick GPS lock-up

Cons
  • No usable software
  • Effectively no documentation
 

Offline dadler

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Re: Economical option for precision frequency reference?
« Reply #187 on: August 06, 2015, 06:10:30 am »
So, I have some information about the RFTG units.

I've shared my personal directory here:

https://www.dropbox.com/sh/osgb29wvgnxag4v/AABzYRcHALPExnaa6hU7MLeua?dl=0

There is some software and an RFTG user manual from 1996. You guys might already have this stuff, but just thought I'd share just in case.

So this is the manual for the older unit that the KS-24361 is patterned on, right?

For anyone thinking of downloading - the software does not run on recent versions of Windows.

Yeah it's an old manual for an ancestor revision, but I was told that most of the communication protocol stuff and other configuration info should be relevant to the newer boxes.

And yeah, I never got the software to work myself but I didn't try that hard. The guy I got the Lucent box from gave it to me--and said he didn't know if it was compatible with the particular Lucent RFTG box or not. I have some more info in paper form, let me "scan" it and upload the PDF.
 

Offline dadler

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Re: Economical option for precision frequency reference?
« Reply #188 on: August 06, 2015, 06:43:27 am »
So I never really looked at the paperwork before, I guess it's not that useful but I scanned it anyways:

https://www.dropbox.com/s/n4nt3yhdt5mc10r/Lucent_RFTGm_II_XO_Notes.pdf?dl=0

Keep in mind that the unit I have is the RFTGm-II-XO, which is different than those with the open enclosures. It has a similar front plate, but the entire enclosure is a big, sealed heat sink. However I believe these are all similar architecture devices.



 

Offline EV

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Re: Economical option for precision frequency reference?
« Reply #189 on: August 06, 2015, 07:07:07 am »
Cons
  • No usable software
  • ...

Have you tried tboltmon.exe? You can get it here under references:

http://www.prc68.com/I/ThunderBolt.shtml#Tboltmon
 

Offline TSL

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Re: Economical option for precision frequency reference?
« Reply #190 on: August 06, 2015, 07:46:27 am »

Have you tried tboltmon.exe? You can get it here under references:

http://www.prc68.com/I/ThunderBolt.shtml#Tboltmon

That's actually a good idea. Trimble have their own language for their GPSDO's called TSIP. It's the only language Thunderbolts talk. Other Trimble's can be made to talk NMEA but probably only after you've spoken to it in TSIP!

regards

Tim
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Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #191 on: August 06, 2015, 08:47:49 pm »
dadler - thanks for scanning and uploading the docs on the RTFG.

EV and TSL - I will give tboltmon a try. I need to fashion an adapter cable before I can connect it up. Fortunately, the pinout is printed right on the front panel. I have to look up the pinout of the standard PC serial port - it may just need a gender changer (aka "null modem").

(Edit) Looks like a standard USB to serial adapter will work. I'll have to order one from Amazon, though, as all the ones here are USB to Serial/Null-Modem (i.e. a female DB9 connector).
« Last Edit: August 06, 2015, 09:07:52 pm by motocoder »
 

Offline TSL

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Re: Economical option for precision frequency reference?
« Reply #192 on: August 06, 2015, 10:57:59 pm »
TboltMon isn't the only program that can read TSIP, but it is mostly aimed at Thunderbolt owners. A better piece of software would be Trimble Studio and/or TSIP talker. You can get them from here...

ftp://ftp.trimble.com/pub/sct/embedded/bin/

regards

Tim
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Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #193 on: August 07, 2015, 05:31:48 am »
I discovered that I can hook up Z38XX to either unit's diagnostic port, and see not just the OCXO data but also the GPS data. Given the GPS board is only in the REF1 unit, this MUST mean that there is some sort of communications link between REF0 and REF1 on the J5 interface cable.

I mention this because there was speculation on the time-nuts mailing list that the interface was very simple voltage-level signalling and the 1PPS signal only. That's clearly wrong, as there would be no way for REF0 to know what satellites REF1 was tracking were that the case.
 

Offline Shock

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Re: Economical option for precision frequency reference?
« Reply #194 on: August 07, 2015, 01:56:51 pm »
I discovered that I can hook up Z38XX to either unit's diagnostic port, and see not just the OCXO data but also the GPS data. Given the GPS board is only in the REF1 unit, this MUST mean that there is some sort of communications link between REF0 and REF1 on the J5 interface cable.

I mention this because there was speculation on the time-nuts mailing list that the interface was very simple voltage-level signalling and the 1PPS signal only. That's clearly wrong, as there would be no way for REF0 to know what satellites REF1 was tracking were that the case.

There is a lot happening on J5.

https://www.febo.com/pipermail/time-nuts/2014-November/087970.html
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Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #195 on: August 07, 2015, 02:24:28 pm »
I discovered that I can hook up Z38XX to either unit's diagnostic port, and see not just the OCXO data but also the GPS data. Given the GPS board is only in the REF1 unit, this MUST mean that there is some sort of communications link between REF0 and REF1 on the J5 interface cable.

I mention this because there was speculation on the time-nuts mailing list that the interface was very simple voltage-level signalling and the 1PPS signal only. That's clearly wrong, as there would be no way for REF0 to know what satellites REF1 was tracking were that the case.

There is a lot happening on J5.

https://www.febo.com/pipermail/time-nuts/2014-November/087970.html

Thanks. There's still a missing piece of the puzzle there, however. As it mentioned in that post, there must be some way that REF0 is able to send commands to the GPS receiver in REF1, possibly proxying through the micro on REF1.
 

Online edpalmer42

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Re: Economical option for precision frequency reference?
« Reply #196 on: August 07, 2015, 06:30:27 pm »
I discovered that I can hook up Z38XX to either unit's diagnostic port, and see not just the OCXO data but also the GPS data. Given the GPS board is only in the REF1 unit, this MUST mean that there is some sort of communications link between REF0 and REF1 on the J5 interface cable.

I mention this because there was speculation on the time-nuts mailing list that the interface was very simple voltage-level signalling and the 1PPS signal only. That's clearly wrong, as there would be no way for REF0 to know what satellites REF1 was tracking were that the case.

There is a lot happening on J5.

https://www.febo.com/pipermail/time-nuts/2014-November/087970.html

Thanks. There's still a missing piece of the puzzle there, however. As it mentioned in that post, there must be some way that REF0 is able to send commands to the GPS receiver in REF1, possibly proxying through the micro on REF1.

There's some current discussion on Time-Nuts on this topic.  Check out the archive:

https://www.febo.com/pipermail/time-nuts/2015-August/093303.html

This behaviour sounds identical to what I saw with another member of the Z38 family.  The Z3817A was made for Motorola.  It listens to a GPS and can report anything it hears, but it has no ability to control the GPS.  It disciplines its OCXO to the incoming PPS.  It looks like they copied this behaviour for the Lucent units.

The Z3817A happens to be the best GPSDO I've got.  When I measure the PPS output, the standard deviation of the period is < 0.1 ns with a max-min range of < 1 ns.

Ed
 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #197 on: August 07, 2015, 08:13:50 pm »
I discovered that I can hook up Z38XX to either unit's diagnostic port, and see not just the OCXO data but also the GPS data. Given the GPS board is only in the REF1 unit, this MUST mean that there is some sort of communications link between REF0 and REF1 on the J5 interface cable.

I mention this because there was speculation on the time-nuts mailing list that the interface was very simple voltage-level signalling and the 1PPS signal only. That's clearly wrong, as there would be no way for REF0 to know what satellites REF1 was tracking were that the case.

There is a lot happening on J5.

https://www.febo.com/pipermail/time-nuts/2014-November/087970.html

Thanks. There's still a missing piece of the puzzle there, however. As it mentioned in that post, there must be some way that REF0 is able to send commands to the GPS receiver in REF1, possibly proxying through the micro on REF1.

There's some current discussion on Time-Nuts on this topic.  Check out the archive:

https://www.febo.com/pipermail/time-nuts/2015-August/093303.html

This behaviour sounds identical to what I saw with another member of the Z38 family.  The Z3817A was made for Motorola.  It listens to a GPS and can report anything it hears, but it has no ability to control the GPS.  It disciplines its OCXO to the incoming PPS.  It looks like they copied this behaviour for the Lucent units.

The Z3817A happens to be the best GPSDO I've got.  When I measure the PPS output, the standard deviation of the period is < 0.1 ns with a max-min range of < 1 ns.

Ed

Now that I have two GPSDO - the Lucent and the Trimble - I've been doing some experiments to compare the two. I also have the (Morion) OCXO in my 53131A frequency counter.

If I hook the Lucent to channel one on my scope, and the Trimble to channel two, trigger off channel one and set infinite persistance, I can get some data on how much the relative phases of the two units drift. It has been steadily improving since I plugged the Trimble unit in. Right now there is as much as 17ns drift between the two, which I think is pretty good. I suspect the bulk of this is the Trimble, probably because it has only been plugged in for a few days. I say this because if I hook up the two GPSDO to my frequency counter, using its internal OCXO as the reference, I can see that the Trimble unit has quite a bit more drift than the Lucent. The Lucent drift is < 0.0003 Hz, whereas the Trimble is closer to 0.001 Hz. Obviously the OCXO in my counter is also not perfect, but I think as a relative measurement this is a valid technique for a rough comparison of the two GPSDO.

 

Offline TSL

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Re: Economical option for precision frequency reference?
« Reply #198 on: August 07, 2015, 10:30:32 pm »

The Z3817A happens to be the best GPSDO I've got.  When I measure the PPS output, the standard deviation of the period is < 0.1 ns with a max-min range of < 1 ns.

Ed

OK... how were you measuring that ? What's your base reference ?

thanks

Tim
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Online edpalmer42

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Re: Economical option for precision frequency reference?
« Reply #199 on: August 07, 2015, 10:43:32 pm »

The Z3817A happens to be the best GPSDO I've got.  When I measure the PPS output, the standard deviation of the period is < 0.1 ns with a max-min range of < 1 ns.

Ed

OK... how were you measuring that ? What's your base reference ?

thanks

Tim

I was using an HP 5370B (resolution of < 50 ps - yes picoseconds) referenced to my Efratom FRT Rb standard.  I made multiple runs of ~1000 readings per run.  Notice that I didn't say what the period was, only what the standard deviation was.  The 5370B reports that directly.  That means the absolute accuracy isn't relevant, just the resolution.  This test measures jitter.  The assumption with any GPSDO is that they've got the basics right and the frequency is correct.

Ed
 


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