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

k4cle at aol.com k4cle at aol.com
Tue Oct 11 17:42:37 EDT 2011


If I recall, the firmware in the RFTGm collects about an hours worth of position info and does an average to establish a self-survey.  The next time you cycle power, it will check the new position against the stored one and if within 50 feet or so, it will use the stored position.  That's probably why it took a while for the LED to extinguish.

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: Tue, Oct 11, 2011 12:49:45 GMT+00:00
Subject: Re: [time-nuts] Lucent RFTG-m-XO GPSDO

The Rx was defective - I just got the new one, hooked it up to my
little test rig anf the antenna, and it happily picked up satellites
and got a position fix.

Swapped it into the box, and found a TTL level copy of the RX data
stream from the encore on pin 2 of the interface connector, so hooked
that up to a TTL->RS232 converter so I could monitor what was
happening.  It all seemed to be tracking OK, although the "No GPS" LED
was still on, so I just left it and after a couple of hours the LED
went out.

Next step is getting the Rb working :)


On Mon, Oct 10, 2011 at 2:41 AM, k4cle at aol.com <k4cle at aol.com> wrote:
> 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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