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Today's Topics:
1. Re: Garmin GPS18x no longer compatible with RTCM (Joe Bennett)
Message: 1 Date: Thu, 28 Jan 2016 20:01:20 -0600 From: Joe Bennett <aprs@ka3nam.com> To: app_rpt-users@ohnosec.org Subject: Re: [App_rpt-users] Garmin GPS18x no longer compatible with RTCM Message-ID: <CAD+1-48xN03rzJQNaedmJ3qZ8u6Jg87Qvq8ot44jPHWRAvVRww@mail.gmail.com> Content-Type: text/plain; charset=UTF-8
I really doubt that a level converter will add enough timing skew to amount to anything. The jitter you see on the internet will greatly outweigh the skew of a level converter by orders of magnitude...
-Joe KA3NAM
On Tue, Jan 26, 2016 at 1:44 PM, James Cizek <james.m.cizek@gmail.com> wrote: > Hi folks, > > Wanted to get this out to you before anyone else bought one thinking they > would work (since this model is specifically called out in the RTCM docs). > > When using a GPS with a Micro-node RTCM for voting, you need to find one > that has a 5 volt Pulse-per-second output. The Garmin lines that is > recommended (GPS 18X, 18X lvc, etc...) > NO LONGER do this! > > This is what I got back from Garmin: > > Mr. Cizek, > > > > I was just told there was a design change with the GPS 18x LVC. The PPS > signal voltage is now 3V. This was something we were not told until today. > We will be making the changes to the online Technical Specifications to > reflect this change. > > I do apologize for the inconvenience. This was a change we were not informed > of. > > > So this line of GPS's will *NOT* work with an RTCM any longer. Talking to > Mark at Micro-node, there is a voltage divider in the RTCM dropping the 5 > volt to 3.3 volt to be compatible with the CPU. With only 3 volts on the > incoming line, there isn't enough making it to the CPU to trigger a state > change and you will get "PPS Timeout" errors and be unable to achieve GPS > lock. > > > I am not sure what kind of timing skew a level converter would introduce, so > it's probably a better bet to just get a GPS that has a 5 volt line (Trimble > Thunderbolt or the similar). > > > There may be a possibility of removing or modifying the voltage divider > inside as well, but without schematics, and unless you have SMD capable > gear, it's unlikely that that is a good solution. > > > Just wanted to let folks know so they don't repeat the brain damage I just > went through figuring this out :) > > > 73 > > James > > KI0KN > > > > > _______________________________________________ > App_rpt-users mailing list > App_rpt-users@ohnosec.org > http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users > > To unsubscribe from this list please visit > http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users and scroll down to > the bottom of the page. Enter your email address and press the "Unsubscribe > or edit options button" > You do not need a password to unsubscribe, you can do it via email > confirmation. If you have trouble unsubscribing, please send a message to > the list detailing the problem.
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End of App_rpt-users Digest, Vol 83, Issue 43 *********************************************