[amsat-bb] Re: Accuracy?

George Henry ka3hsw@earthlink.net
Fri Aug 25 10:04:11 PDT 2006

With the Motorola Oncore software I am using, I have found the reported time to exactly match WWV.  I assume that the software takes leap seconds into account, though I have not checked the documentation.  A friend who works at Motorola did the initial set-up

-----Original Message-----
>From: Ray McKnight <shortsheep@worldnet.att.net>
>Sent: Aug 25, 2006 1:16 AM
>To: George Henry <ka3hsw@earthlink.net>
>Subject: Re: [amsat-bb] Re: Accuracy?
>You are aware that GPS time and "earth" time are two different critters?
>The GPS constellation is not adjusted for leap seconds, so the time your
>GPS receiver displays is something like 13-14 seconds off actual earth time.
>Could make for some big problems trying to track a highly eliptical orbit
>or even LEO with that much error.
>----- Original Message ----- 
>From: "George Henry" <ka3hsw@earthlink.net>
>To: "amsat bb" <amsat-bb@amsat.org>
>Sent: Thursday, August 24, 2006 21:27
>Subject: [amsat-bb] Re: Accuracy?
>> It depends on the level of automation of your station...  if you are using
>> fixed antennas, you only need enough accuracy to know when the satellite
>> in view.  If you are using rotor control, it depends on the beamwidth of
>> your antennas ( the narrower the beamwidth, the more critical the aiming
>> becomes).  If you are using doppler control, then very high accuracy is
>> needed:  a few seconds of error can translate to several hundred hertz of
>> doppler shift on a high pass.
>> I have my XP machines set to check an internet NTP server every 4 hours.
>> For Field Day, I use a GPS receiver to keep the PC clock dead on, and
>> use GPS to set my station coordinates accurately when portable.  And when
>> doubt, I update my keps right before operating, and at least once a week
>> otherwise.
>> George, KA3HSW

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