[time-nuts] Symmetricom TimeSource 2700

Tue May 1 23:00:53 UTC 2012

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
> >>
> >>
> >>
> >>
> >>
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