Re: [time-nuts] unknown GPSDO
The original Brooks Shera unit was 20 years ago and is pretty well documented in QST and his website. In the original the loop filter timeconstant was set by jumpers or DIPswitches. And I think the EFC gain factor was set somewhere else (DIPswitch? Resistor network? Both?) Shera's webpage documents some improvements and changes up through 2001 but there have been an incredible number of variations out there in the wild as folks move parameters that used to be set in hardware/DIPswitches to firmware with LCD config screens etc. I think the OP's unit shows a decade or more of evolution past what Shera documents. Is there a "Brooks Shera GPS family tree" out there showing recent evolution of the design? Tim N3QE On Tue, Jul 18, 2017 at 11:10 AM, David C. Partridge < david.partri...@perdrix.co.uk> wrote: > ISTR that you started it with a short time constant to get locked, and > once you had lock you would increase the time constant in a few steps to a > final value of (say) 1000s or so. > > Dave > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker > Esper > Sent: 18 July 2017 14:15 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] unknown GPSDO > > Thanks so far. I will have a look at the docs. > > The machine is running well, particularly the OCXO is performing very good > when free running (without GPS signal). It is stable and its ADEV looks > good (2E-10 at 10s). Not so the overall ADEV (when GPS locked) > (1E-5 at 10s). It seems to not having the right filter time constant what > had to be much longer. As I understand the documents, the filter constant > can be programmed and I will experiment whith that this afternoon. > > Thank you > > Volker > > ___ > 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.
Re: [time-nuts] unknown GPSDO
ISTR that you started it with a short time constant to get locked, and once you had lock you would increase the time constant in a few steps to a final value of (say) 1000s or so. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: 18 July 2017 14:15 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] unknown GPSDO Thanks so far. I will have a look at the docs. The machine is running well, particularly the OCXO is performing very good when free running (without GPS signal). It is stable and its ADEV looks good (2E-10 at 10s). Not so the overall ADEV (when GPS locked) (1E-5 at 10s). It seems to not having the right filter time constant what had to be much longer. As I understand the documents, the filter constant can be programmed and I will experiment whith that this afternoon. Thank you Volker ___ 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.
Re: [time-nuts] unknown GPSDO
Thanks so far. I will have a look at the docs. The machine is running well, particularly the OCXO is performing very good when free running (without GPS signal). It is stable and its ADEV looks good (2E-10 at 10s). Not so the overall ADEV (when GPS locked) (1E-5 at 10s). It seems to not having the right filter time constant what had to be much longer. As I understand the documents, the filter constant can be programmed and I will experiment whith that this afternoon. Thank you Volker Am 17.07.2017 um 16:36 schrieb EB4APL: > Hi Volker, > > Browsing on my documentation I found that 402NE wast the last version of > Brooks Shera's (W5OJM) code for the PIC, made in collaboration with > Bob Leichner (WO6W). Probably this ham was one of Shera´s friends who > developed the last version and published the sources. > > I include below the instructions that Shera sent me with version 402NE > > Regards, > > Ignacio, EB4APL > > > > W5OJM GPS-DISCIPLINED FREQUENCY STANDARD... ___ 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.
Re: [time-nuts] unknown GPSDO
The July 1998 QST had an article on a GPSDO he designed. That may help. 73, Dick, W1KSZ Sent from Outlook<http://aka.ms/weboutlook> From: time-nuts <time-nuts-boun...@febo.com> on behalf of Volker Esper <ail...@t-online.de> Sent: Monday, July 17, 2017 2:47:42 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] unknown GPSDO Hello dear fellow time-nuts, Last weekend I bought a selfmade GPSDO at the fleamarket for a very adequate price. Now I need some more information about it to operate it. It seems to work fine, but I don't understand the displayed numbers, the menu, the lamps, the DIP switches... Can you help to identify it? I couldn't find it on the internet. Here are some fotos... When powering up, the display shows "Brooks Shera GPSVCXO 2014". Enthough that might give me a clear hint to identify it, I only found the starting docs from 1998 or so, but not the actual board. Thanks a lot! Volker ___ 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] Unknown GPSDO
Do any of you know any details of an unknown GPS DO. Visual GPS identifies it as a Motorola VP/GT. It fas a Motorola 5 MHz. packaged oscillator and a Motorola GPS receiver. The receiver is apparently a 6 channel model. One of the circuit boards are marked 1991-1994. It has 1 Hz, pulse and 5 MHz. on the back and front . but the back is only activated when it is in service It also has a RS232 interface on the back and two connectors I don't understand. One is a two row 10 pin header the other connector is a RJ (similar to telephone) connector. It apparently works, but even when the in service light is on it it is still not locked when I compare it to anther GPSDO Any source of information on this unit is appreciated Bill K7NOM ___ 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.
