[time-nuts] Falling Edge Error

[Magnus Danielson]

From: "Randy Warner" <Randy at synergy-gps.com>
Subject: Re: [time-nuts] Falling Edge Error
Date: Mon, 14 Aug 2006 10:00:35 -0700
Message-ID: <D6D8D27B5219D649A005529978F79137133BF0 at SBSERVER.Synergy-GPS.sbs>

> Guys,

Randy,

> Maybe it would be better to call it the "leading" edge?

It got my vote at least. ;O)

> I have actually
> sent out a couple of our SynPaQ receivers with the 1PPS jumper in the
> "inverted" position per customer request. There always have to be a
> couple of oddballs.....

Yeah... but there is another reason, there is infact an IRIG format which sends
time-code in the PWM of the PPS (or indeed other frequencies), but will leave
the rising edge intact. Quite handy infact. I have considered using it. That
IRIG format isn't perfect however. It doesn't convey all the info you want. Ah
well. A good format would convey UTC time, date and TAI-UTC difference.

Cheers,
Magnus

> Randy 
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Normand Martel
> Sent: Monday, August 14, 2006 4:40 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Falling Edge Error
> 
> If i'm not wrong, virtually ALL GPS modules have their timing
> standardized on the RISING edge and do NOT guarantee anything about the
> falling edge.
> 
> Glenn's measurements confirm that fact... Ideally, to get sure the users
> will use the rising edge, that signal shall be a sawtooth!!! (or
> simpler: a random falling edge.)
> 
> 73 de Normand VE2UM
> Montreal, Qc. Canada
> 
> --- Glenn <glenn at net127.com> wrote:
> 
> > 
> > I just tried a quick test with my HP 5334A, with a LPRO to TVB divider
> 
> > on channel A and an Oncore UT+ on channel B.
> > 
> > frequency difference:
> > measured on the falling edge: 37E-9 Hz measured on the leading edge: 
> > 6.7E-9 Hz
> > 
> > Both measurements are from the rising or falling edge of the 1 PPS of 
> > the GPS, 100 sample average.
> > 
> > cheers,
> > glenn
> > 
> > 
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