[time-nuts] Lucent RFTG-m-XO GPSDO

k4cle at aol.com k4cle at aol.com
Sun Oct 9 18:41:28 UTC 2011


Hi Peter, yes it sounds like the UT+ is defective if it never gets any sats.  You can probably find one on eBay.  Someone probably fired RF into the receiver front-end and zapped it.  I think the antenna you are using should be OK.

I will look for my drawings on this unit and send copies to you.  And I know I have the software too, just need to find it!

I have read in some of the notes here on time-nuts that people may be able to use RS232 for communicating with the RFTG units.  But it was designed for RS422 and I would suggest you use RS422 for best results.  I use a little RS422-4S232 converter which has worked fine for me.

The early units had FRS rubidiums in them.  The LPRO was used in the newer units.  So, you have the more recent design.  
Connected by DROID on Verizon Wireless

-----Original message-----
From: Peter Bell <bell.peter at gmail.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sun, Oct 9, 2011 05:52:25 GMT+00:00
Subject: Re: [time-nuts] Lucent RFTG-m-XO GPSDO

On Sun, Oct 9, 2011 at 3:31 AM, k4cle at aol.com <k4cle at aol.com> wrote:
> Peter, do you have the software for this unit?  The GPS antenna is supposed
> to draw apx. 20 mA at 5 volts in order for the NO GPS LED to turn off.  AT&T
> (Lucent) used the MicroPulse timing antenna (later sold and now provided by
> PCTE).  You are correct in that Efratom used the Motorola UT+ 8 channel GPS
> receiver on these units.  The rubidium companion box used the data from the
> same receiver (via an interconnect cable between the two units).  Let me
> know if you have questions on this unit, Regards, Doug....
> Connected by DROID on Verizon Wireless
>
> -----Original message-----
> From: Peter Bell <bell.peter at gmail.com>
> To: time-nuts at febo.com
> Sent: Fri, Oct 7, 2011 14:13:31 GMT+00:00
> Subject: [time-nuts] Lucent RFTG-m-XO GPSDO
>
> I have been playing with one of these units, and noticed that there
> has been some discussion on them before on this list, so I wondered if
> anyone might have any suggestions.
>
> Basically, the unit powers up correctly, but the "No GPS" LED never
> goes off - this obviously could be because it's broken or doesn't like
> my antenna, but with some of these telecom GPSDOs you have to manually
> trigger a site survey if you move them to another location. Does
> anyone know if this Lucent box is like that?
>
> Everything else seems to be working - once the "OK" light comes on the
> 15MHz output is enbled, the "No GPS" LED goes from solid to blinking
> if you disconnect the antenna - it just doesn't want to get GPS lock.
>
> I suppose I could pull the Oncore board (a UT+ according to the label)
> out of it and test that on it's own - but I thiought I would see if
> maybe it's a known issue first.
>
Hi, Doug

I don't have any documentation at all - just the actual box.  The
antenna is one that originally came with a Furuno marine GPS, but the
spec looks plausible (+5V @ 40mA, Internal L1 preamp with 26dB gain -
and it has worked with several other GPS units without problems.

I just pulled the oncore out, and connected it up outside the box -
and it doesn't work.  It passes the self test with a response code of
0000 (or 8000 with the antenna disconnected / 4000 with a short on the
antenna socket - so it seems the current consumption is OK) - but no
matter how long you leave it it still says it's tracking 0 satellites,
although it happiy generates status reports.

I wonder if this UT+ version is expecially sensitive to the antenna?
I remember that the oncore VP would work with pretty much anything you
hooked up to it.  Of course, it's equally possible that the GPS module
is defective.

I'm tending towards broken - I also got an RTFG-m-RB with this unit,
and that has a faulty LPRO-101 in it (it's probably fixable - it looks
like the FET that heats up the Rb cell had gone open circuit) - and
the two units together only cost me $40 supplied on a "status unkown,
but likely defective" basis. I should get at least $40 of
entertainment out of trying to fix them :)

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