Hi Nigel, Yes, I have the same version. We might have got it from the same UK epay source. The GPS did not work reliably, and I did start testing that module outside the Trak unit, and also tried VP(8chan) receivers that I had. Did not really conclude why the GPS did not behave properly. I was, like you, disappointed by the lack of IRIG and other features that are in the standard units. I also drew the conclusion this was a "high volume" special model, where it was cost effective to eliminate all - for the specific application - unuseful outputs.
However it is a very decent size OCXO inside. The phase measurement Oncore model is interesting, since I have seen very few GPSDOs that use phase information. It gives the possibility to reduce the short term GPS noise to cm/s level. However this is probably lost in the PPS generation hardware, since the Oncore does not lock its internal crystal to the external OCXO. -- Björn > Hi Bjorn > > Is yours also the cut down 2.084MHz version, or do you have a "proper" > 8821B with a more useful GPSDO frequency and all the outputs fitted? > I think this one was originally used in a trunked radio system. > > I've just checked and the fitted VP Oncore is the B8121Z116, so perhaps > the same module, but I'd forgotten until I looked again that the unit is > without the IRIG-B output as well as the Low-Rate output that normally > allows a > variety of pre-set pulse rates, hence my "cut down" comment. > > The Low-Rate ouput speciification suggests some interesting possibilities > for experiments in conditioning other oscillators, as amongst some very > slow pulse rates it also offered an option of 1 MPPS. > Unfortunately, not only are the connectors not fitted but quite a lot of > presumably associated PCB components in that area are also missing. > > Do you have a manual for the 8821B? > I've only ever found a manual for the 8821A, although I suspect the only > significant difference may be the fitting of the larger B7A OCXO to the > 8821B, which necessitated the height increase to 2U, but it would be nice > to be > able to compare them. > > regards > > Nigel > GM8PZR > > In a message dated 21/08/2012 21:05:02 GMT Daylight Time, > b...@lysator.liu.se > writes: > > Hi Nigel, > > Have one of those Trak 8821B too. It is a bit interesting since the > Motorola Oncore VP inside mine has the Z option (phase measurement). > > -- > > Björn > > > _______________________________________________ > 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.