[time-nuts] Symmetricom TimeSource 2700

[Bob Camp]

Hi

CDMA is very much alive and kicking in the US. 

Bob

On May 1, 2012, at 7:00 PM, paul swed wrote:

> Thought the cdma signals were all gone.
> 
> On Tue, May 1, 2012 at 6:50 PM, Pete Lancashire <pete at petelancashire.com>wrote:
> 
>> I am playing around with a OT-20 "Office Time" that I pulled out of a
>> dumpster some time ago. I've only just powered it up last weekend and
>> it without an antenna will illuminate its CDMA green status LED in
>> about 10 minutes. I've not tried an antenna or hooked up a terminal to
>> its serial port.
>> 
>> -pete
>> 
>> On Tue, May 1, 2012 at 9:40 AM, Mark Spencer <mspencer12345 at yahoo.ca>
>> wrote:
>>> Sorry to resurrect an old thread, but I thought someone might find this
>> of interest.
>>> 
>>> I purchased a 2700 intending to harvest the PRS10.   Prior to cracking
>> open the case I powered up the unit to ensure it was basically working so I
>> could return it if needed.   I noticed that despite not having an antenna
>> connected it seemed to find and track CDMA signals and after a few hours
>> the 10 Mhz output was in a few parts of 10E-12 of my GPSD0.
>>> 
>>> After a bit of investigation I found the following
>>> 
>>> Adding an external antenna didn't seem to make much difference to the
>> performance.
>>> 
>>> The 1pps output is approx. 75ms out of sync with the 1pps output from my
>> Fury GPSD0.
>>> 
>>> From time to time the 10 Mhz output experiences phase jumps of several
>> tens of ns.   Manipulating the unit (ie. connecting to the RS 422 port) may
>> induce this.  Power cycling the unit seems to cure the problem and the unit
>> usually takes an hour or two to re lock.  It's possible that the lack of a
>> proper ground in my instalation may be causing some of the issues as well.
>>  This problem would be a show stopper for me in terms of using this unit
>> to replace my GPSDO's.  I'm not sure if this issue is specfic to my unit or
>> not.
>>> 
>>> I've attached some initial ADEV plots showing the typical performance of
>> the 10 Mhz output vs three of my other references.  (I wouldn't put a lot
>> of emphasis on the results of taus of less than 100 seconds or more than
>> 6,000 or so..)  I doubt I'm going to put much more time into this unit but
>> it's an interesting novelty in it's original state.   The results of other
>> units may well differ (:
>>> 
>>> Regards
>>> Mark Spencer
>>> 
>>> 
>>> --- On Thu, 11/24/11, Charles P. Steinmetz <
>> charles_steinmetz at lavabit.com> wrote:
>>> 
>>>> From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
>>>> Subject: Re: [time-nuts] Symmetricom TimeSource 2700
>>>> To: "Discussion of precise time and frequency measurement" <
>> time-nuts at febo.com>
>>>> Received: Thursday, November 24, 2011, 11:17 PM
>>>> Kevin wrote:
>>>> 
>>>>> I use the Craft connector for monitoring with BTMon
>>>> rather than the RS-232 port.
>>>>> It appears the Craft output, while spontaneously
>>>> emitting alarm/events, does respond
>>>>> to queries from BTMon on the Craft input.
>>>> 
>>>> Everything I reported previously involved the Craft port
>>>> feeding a PC COM port using the RJ45-to-DB9 cable supplied
>>>> by Symmetricom.
>>>> 
>>>>> Do you happen to have a RS-422/485 interface? I don't,
>>>> but I'm interested to see
>>>>> if any spontaneous output occurs on the TOD port.
>>>> 
>>>> I have a 422/485 card here somewhere, but I haven't used it
>>>> (maybe even seen it) in more than 10 years.
>>>> 
>>>> I poked a scope at the TOD jack.  The TS2500 manual
>>>> says that (in a TS2500) Pin 1 should be PPS (positive), Pin
>>>> 6 should be PPS (negative), Pin 5 should be TXA output
>>>> (positive), Pin 9 should be TXA output (negative), and Pins
>>>> 7 and 3 should be a 20 V external supply positive and
>>>> return, respectively.
>>>> 
>>>> I found PPS positive and negative on Pins 1 and 6.
>>>> Logic low is about 1.2 V positive with respect to case
>>>> ground, and logic high is about 3.8 V above case ground, for
>>>> a logic range of approximately 2.6 V.  The PPS pulses
>>>> are 500 uS wide with rise and fall times of ~20-25 nS.
>>>> 
>>>> I did not see any data on the TXA outputs -- the positive
>>>> TXA output just sits at logic low and the negative TXA
>>>> output sits at logic high.
>>>> 
>>>> There is 20 V between Pins 7 and 3.  As for the
>>>> unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins
>>>> 4 and 8 sit at nominally 0.168 Vdc.  All three have
>>>> around 20 mVp-p of hum and noise.
>>>> 
>>>> While I was at it, I poked at the RS232 connector, as
>>>> well.  Pin 3 (TX Data) has a 16 or 17 mS burst of data
>>>> every 5 seconds (approximately), from -10 V to +10 V with
>>>> respect to case (henceforth, 232 low and high,
>>>> respectively).  Between bursts, it sits at 232
>>>> low.  Pins 4 and 7 (DTR and RTS, respectively) sit at
>>>> 232 high.  All other pins sit at ground.
>>>> 
>>>> Best regards,
>>>> 
>>>> Charles
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.