Thought the cdma signals were all gone. On Tue, May 1, 2012 at 6:50 PM, Pete Lancashire <p...@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 <mspencer12...@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_steinm...@lavabit.com> wrote: > > > >> From: Charles P. Steinmetz <charles_steinm...@lavabit.com> > >> Subject: Re: [time-nuts] Symmetricom TimeSource 2700 > >> To: "Discussion of precise time and frequency measurement" < > time-nuts@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@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@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@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.