[time-nuts] Introduction and info about a Lucent RFTG
GandalfG8 at aol.com
GandalfG8 at aol.com
Sat Jul 5 08:06:03 EDT 2014
When you refer to one "side" or the other, do you have the complete RFTG
unit with the two modules?
I only have the internals of the Rubidium module so would hardly claim to
be an expert on these, or on much else for that matter:-), but as I
understand it from the documentation this is a "reduntant" system, in that either
the GPSDO or the Rubidium module is active at any one time with the other in
In other words, there's no suggestion that the Rubidium module is locked to
GPS, it is indeed free running, whilst the GPS module is used to
discipline its own crystal oscillator.
However, although the "free running" Rubidium module will need occasional
adjustment, as opposed to the GPSDO wich shoudn't, a free running Rubidium
reference is still not something to be sneezed at.
Section 2.1 "RFTG Functionality", in the documentation refers to this in
There was a fair bit of discussion here at one time regarding these so I'm
surprised you haven't found more in the archives. For example, another list
member, Skip Withrow, produced an article in January 2013 detailing how to
modify the RFTGm GPSDO to obtain a 10MHz output, which he suggests should
also apply to the earlier versions and I've also seen information on the
Because my Rubidium module arrived with just the two attached PCBs and no
outer metalwork whatsoever it was easier for me anyway to just put the
15MHz generator board to one side and use the interface board only with its
special D connector still attached to make the thing functional.
If I'd had the complete unit, including metalwork, I would probably have
approached it differently.
On my unit at least the actual Rubidium module was an Efratom FRS and
there's documentation available online for these should you wish to run it
However, it would seem to me that without too much work, and utilising the
existing metalwork, these two units between them could provide the basis
for a 10MHz Rubidium Standard plus a separate 10MHz GPSDO, but turning them
into a GPS disciplined Rubidium unit perhaps not quite so
In a message dated 05/07/2014 07:38:44 GMT Daylight Time, dencohe at gmail.com
Thank Rex and Paul for the replies
>From what I understand my RFTG has a GPSDO on oneside that has a crystal
oven inside it, and a rubidium source on the other side. The rubidium
source takes a signal from the GPSDO side and uses that for longer term
stability. But If I am understanding you, Rex, that the rubidium is really
not a gps locked oscillator and just a free running device. I will start
tearing down the unit to figure out if I can make something more usable out
of it. I will make sure to document it and post it somewhere on the web. I
read somewhere on this group that there is a way to bypass the 15MHz
generating circuit and use the existing hardware amplifier and distribution
at 10MHz. I will also be looking into that as well. Rex, you are correct as
there is no power supply inside and I have it hooked up to a open frame
type switching supply externally.
Paul - I will be setting up my GPS antenna shortly and trying to get it to
lock to GPS for a more precise reference.
On Fri, Jul 4, 2014 at 9:38 PM, Rex <rexa at sonic.net> wrote:
> Several years ago there were a number of these showing up pretty cheap
> eBay, so I bought one. As I recall there were a couple of similar
> with some differences so take this recollection with a grain of salt.
> I did some tracing of the internals on the one I had and found the
> rubidium unit had no connection on the tuning pin (C-field) to the board
> circuits. So it was free running, only for backup in the system, and not
> GPS lockable. I don't remember there being any useful power supply in the
> box, so my advice would be to remove the LPRO rubidium and use it
> (It does need heat sinking, so maybe some parts of the box mechanicals
> useful.) In my opinion, working out how to use the supporting circuit
> is not worth the effort, unless you really have a need for the 15 MHz
> You should be able to find documentation for the internal module LPRO
> rubidiums on the web. I haven't looked today but KO4BB site probably has
> On 7/4/2014 1:47 PM, Denver wrote:
>> Hi all,
>> My name is Denver I am currently a freshman in college and the time bug
>> struck me. I recently acquired a Lucent RFTG on ebay to have a time
>> standard for my lab(and yes already realize its 15MHz output but may be
>> able to change that and or just use the 10MHz test point from the
>> source). I made a power connector for it. Now that I have power applied
>> sort of verified its operation I am looking for more info about the
>> connectors on the front panel. I have the KO4BB user documentation on it
>> but it doesn't mention much about connectors and pinouts. I also have
>> already searched the group for other mentions of the RFTG but all I am
>> to come up with is some of the newer models the -m and such. Maybe one
>> you could help point me in the right direction or give me some other
>> on how to get more use out of this unit.
>> Thanks in advance
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