[time-nuts] Datum/Symmetricom TS-1200

Bob Camp kb8tq at n1k.org
Sun Mar 27 16:29:36 EDT 2016


Hi

Telecom Rb prices have been running in the $100 to $150 range for quite a while. The same is true of various surplus GPSDO’s with OCXO’s in them. If you hop in your time machine and go back about 5 years ago, for about a year the Rb’s came in (on and off) below $50 and GPSDO’s might come in below $100. Before that prices ran around what they are today on “what we have in stock”. The model numbers have changed, but the prices are about what they have been for at least 10 years. 

A GPS disciplined VCXO is not going to be very stable. The GPS signal is very noisy over a few seconds to a few hours. You need to do a lot of averaging to clean it up. While you are busy averaging, you need a “flywheel” to provide a clean and stable output. That’s where the OCXO comes in. 

Dropping an OCXO (or Rb) into a TCXO based box is just about guaranteed to require some changes to the firmware. On many boards I have seen there are component changes as well. Finding any of that documented …. not easy at all. 

If you want a lab standard, save up and get a surplus GPSDO. A surplus Rb still needs to be calibrated and then you are right back to needing a GPSDO.

Bob

> On Mar 27, 2016, at 3:56 PM, Bob Brannigan <brannigan at shaw.ca> wrote:
> 
> Hello All! 
> 
> Brand new here and hoping for some advice. This list looks like a great resource. I have Googled the list so I hope I'm not asking something already answered. Sorry in advance if this is the case. 
> 
> I was looking for a Rubidium 10mhz standard for my test bench but it looks like the prices have jumped. A friend just offered me an old TS-1200 GPS NTS. It turns out the switching supply is toast so I can either fix it, buy a new one, or cobble something together temporarily to make sure everything works first. 
> 
> I am more interested in the frequency standard than time and position, but having an NTS for my network is a bonus. It has the basic VCXO. I noticed that the PCB has footprints for an OCXO and a rubidium standard. From the time-nuts list I have learned that the VCXO is disciplined by the GPS, so (I think) the only time that XTAL stability would matter would be if GPS lock was lost or if the unit was switched to IRIG, or of course, if it was standalone. 
> 
> So, my questions are: 
> 
> - Would I gain much, if anything, by switching over to an OCXO or rubidium? 
> 
> I am taking a guess that the OCXO is a Datum 105243-002 but I drew a blank on the possible Rb module. 
> 
> - Does the software also use IRIG data to discipline the VCXO? 
> - Would the software recognize the change in frequency standards, or would it even care, or is it a different Rev.? 
> - Is there a service manual or perhaps schematics for the TS 1200? 
> 
> Thanks in advance for any advice, or if my assumptions are off base. I'm looking forward to getting this rig up and running. 
> 
> Regards, 
> 
> Bob 
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