[time-nuts] Lucent RFTG-m-RB

Bob Camp kb8tq at n1k.org
Sun Sep 4 15:20:21 EDT 2016


The units you describe came in a couple of different variations. They all work pretty much the same way, but there are subtle differences. I will stick with what is common:

> On Sep 4, 2016, at 8:04 AM, Anton Moehammad via time-nuts <time-nuts at febo.com> wrote:
> Hi All,I understand this RFTG-m-RB and RFTG-m-XO already discuss many-many time in the past but I need to ask for something that I don't clear enough..1. my GPS antenna position can give 6 to 8 satellite at once times with a good signal is that enough ?

As long as it does not drop below 3 sat’s you are probably ok. 

> 2. I believe the GPSDO and Rubidium are "comparable" in stability

The Rb is much less accurate than the GPSDO when the GPSDO is locked to GPS and after it has been running for a few days. 

> so I do not fully understand why I need Rubidium GPSDO ?3. I understand Rubidium has "lifetime" are this lifetime count from when its use or from its manufacture ?

Mostly it is a number of hours of “running time” rather than days from manufacture. The lifetime might be as short as 5 years on some versions of Rb’s and as long as 25 years on others. Even within a batch of units, the lifetime might vary 2:1. 

> 4. How good the psu I need ? I see inside of my RFTG-m-RB and RFTG-m-XO they use an DC to DC converter are 24v switch PSU is good enough or must I linear PSU ?

A switching regulator power supply is fine. You can get away with an un-regulated “bulk” supply. 

> 5. How to sure my RFTG-m-RB and RFTG-m-XO combo are in spec ?

They are specified to deliver CDMA signals to operate a cell tower. In this application, the information is available on the serial output(s) after all of the interconnect cables have been hooked up. 

> 6. The best and the only calibration place I know here in Indonesia are Indonesia NMI with a PHM the cost for calibration is "not much" but the time is long (6 month) with 10-e10 maybe 10-e11 are this kind of calibration (without adjustment) is to much ?

They should be within about 100 ns of GPS time. The frequency accuracy is rated at 1x10^-8, but is typically much better. It is not unreasonable to guess that it is better than 1x10^-10 in frequency almost all of the time (when locked). 

> Sorry for my Java English and for so many basic question.

Not a problem, I unfortunately have absolutely no excuse for my poor English ….


> Thank You
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