Hi GPS receivers have gotten better over the years. The early Motorola receivers were relatively deaf compared to a TBolt. A TBolt is a bit deaf compared to a LEA5-T.
My bet for the actual problem is that HP is doing elevation masks and s/n detection in their firmware rather than in the receiver. Bob On Nov 5, 2012, at 10:11 PM, Ed Palmer <ed_pal...@sasktel.net> wrote: > Hi Azelio, > > On 11/5/2012 4:09 PM, Azelio Boriani wrote: >> Very interesting... is it using the binary protocol? > > Yes, standard Motorola binary format. > >> Maybe a serial link >> error, the binary protocol has a checksum (yes, NMEA too). Check the serial >> link levels with a 'scope, maybe that the Z3801 firmware waits to see some >> consecutive errors before actually reporting that something is wrong, >> meanwhile the satellite number is set to 0. > > The link is TTL, not RS-232. The power supply to the VP is 4V93 and the > logic levels on the scope are maybe 0V2 and 4V8 so no problem there. > > I've tried disconnecting the 1 PPS and/or the data line from the VP to the > Z3801A. The Z3801A reports the loss of 1 PPS quickly, but in either case, > waits for quite a while before getting upset. I haven't been able to corrupt > a message to see what effect that has, but I think it would have to be a very > specific form of corruption to be accepted. In any case, although that might > explain the drop to zero satellites tracked, it wouldn't explain the > situation where the VP reports fewer satellites tracked than the Z3801A does. > This occurs frequently. I don't know if the two situations (drop to zero > and fewer satellites) are related or not. > > By the way, I was initially using SynTac and Z38XX to gather the data. Since > I couldn't believe the results, I replaced both with a program I quickly > hacked together to gather and parse the raw data from both units. The > results were the same. > > Ed > >> On Mon, Nov 5, 2012 at 10:38 PM, Ed Palmer <ed_pal...@sasktel.net> wrote: >> >>> I've had a Z3801A for about a year. It's always had an issue where the >>> number of satellites tracked will drop to zero for one or two readings and >>> then jump right back where it was ( often at 5 or 6 satellites ). This >>> often (but not always) affects the EFC and/or PPS and/or HUP. My Tbolt is >>> running on the same antenna via an HP58536A splitter with no problems. >>> I've changed cables and splitter ports with no improvement. I've also >>> checked the power supply voltages and the frequencies of the two crystals >>> on the Z3801A board. All are fine. >>> >>> I assumed that the VP was flaky so I recently pulled it out for testing >>> and found no problems. I then tapped into the link between the VP and the >>> Z3801A and found that the number of tracked satellites reported by the >>> Z3801A is often less than the number reported by the VP. Specifically, >>> I've seen the VP report 6 satellites tracked at the exact same second that >>> the Z3801A is claiming that there are no (zero) satellites tracked. >>> >>> Does anyone know if there are any hidden parameters that the Z3801A is >>> using to decide if a satellite is acceptable? I looked through the manual >>> but I couldn't find anything. Is there a command I'm missing? >>> >>> Thanks, >>> >>> Ed > > _______________________________________________ > 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.
