In a message dated 22/08/2012 21:30:36 GMT Daylight Time, [email protected] writes:
Hi Nigel, > > With regards to the Oncore VP carrier phase measurement option, I'm not > too sure that the 8821B does actually make use of that. The "Z" is a pure software option, to enable the phase capability already in all of the VP receivers. So you pay extra, but get exactly the same hardware. Since they optimised away IRIG and other function, I find it unlikely they would have premium Z options in the VP if it was not used. I should try to snoop on the communication between the VP and the microcontroller in the 8821. -------------- Hi Bjorn It's obviously difficult to be sure one way or the other without checking as you suggest, but I was also taking into consideration some Motorola published data from 1996 and 1998. The information provided in "Oncore Product Summary" of October 1996, and "Oncore Model Number and Feature Cross-Reference" of October 1998, is quite concise so perhaps nowhere near the whole story, but it does indicate that whilst four of the six VP models available in 1996, two with the Z option and two without, had a specified 1PPS accuracy of less than 50ns, which was otherwise matched only by the UTplus, amongst the VP models available at the end of 1998 it was now only the Z versions that offered this degree of accuracy. Not only did the 1998 Z versions match the UTplus for 1PPS accuracy, they also offered a Differential GPS option which the UTplus did not, although perhaps that wasn't over important in this instance, and they were also the only Oncores to offer Raw Satellite Data, again perhaps not particularly relevant but all of which to me still suggests there could have been other reasons for choosing them besides the carrier phase option, which ironically isn't even listed amongst the options in the 1998 "Feature Cross-Reference" list:-) I'm not trying to make a case either way, just keeping an open mind and still as unsure as I ever was:-), but it does seem that when these 8821Bs were produced the three Z versions of the VP were probably the best all round performers in the range at that time, and that's not even considering the carrier phase option, so perhaps just generally perceived as the best bet regardless. Aside from that, I've had my unit powered up for over 90 minutes now and it seems to be settling down ok. 20 minutes or so after power up the status light came on, stayed on for a short while, and then proceeded to flash at what seemed like one flash per second for another 20 minutes or so before lighting up permanently again and staying on ever since. I don't remember seeing it flashing before, and so far I've only found reference in the 8821A manual to it being either on or off, any ideas on that? In what way were you seeing GPS problems? I've got some commands from the manual that produce an error message rather than the indicated response but I'm assuming that's a firmware difference, and generally all is as I would expect, with regards to satellites tracked, position data, etc etc. What I can't do right now is any accurate monitoring of the output frequency or 1PPS, just about everything round here is powered down whilst I run in some new cables, but I would say all is looking pretty good so far. Regards Nigel GM8PZR _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
