[time-nuts] Symmetricom TimeSource 2700

Tue May 1 19:08:08 UTC 2012

The problem is I don't have the software for the unit, but based on the behaviour of the alarm and status led's I'm confident it is locked.  The symmetricom site may have the software but I would need to agree to an eula prior to downloading which I don't want to do with my work account.  So far symmetricom hasn't approved my request for a personal log in to their site.  

I may try again with another email address (:

------------------------------
On Tue, 1 May, 2012 2:31 PM EDT Bob Camp wrote:

>Hi
>
>The "upstream" time source may or may not be very good. Since it's PCS at
>1.9 GHz and not 900 MHz CDMA, the carriers have a lot of wiggle room. You
>can go in and fiddle which signal it tracks. 
>
>Bob
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Mark Spencer
>Sent: Tuesday, May 01, 2012 12:41 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Symmetricom TimeSource 2700
>
>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
>> 
>> 
>> 
>> 
>> 
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>
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