[time-nuts] GPSDO using 100Hz

[ernieperes at aol.com]

Hii Warren,

have a look on this 
link...http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm

and he is using the 10KHz...rpt 10KHz not the 100Hz......compare with 
your circuit diagram... / I would like to see / or the other solution 
just make the same circuit and with your testing method chk both 
unit.......with the same OCXO....
the jupiter eng board is still available in the German Ebay....

Rgds Ernie.




-----Original Message-----
From: WarrenS Email <warrensjmail-one at yahoo.com>
To: Discussion of precise time and frequency measurement 
<time-nuts at febo.com>
Sent: Mon, 24 Nov 2008 12:49 pm
Subject: [time-nuts] GPSDO using 100Hz



Ulrich Bangert

Thanks for the great Information.

>UR) James Miller, G3RUH, also uses the 100 Hz signal
Thanks, that is what I was asking for, other people that were using the 
100Hz.
Now if I could just figure out how to post a response under an existing
thread, and not have it start a new one I'd be happy.

Concerning your other comments:
>UR) it's neither specifically new nor ...
I did not mean to imply that the 100Hz was new or its use was 
discovered by me,
Mostly I'm wondering why it is so little used, and I'm looking for 
other people
using it.
Something that I can do with the 100Hz that you probable have not seen 
before is

the ability to make a GPSDO similar to Brooks Shera's processors based 
unit
using just 3 standard off the self 74HC IC's and a pretty crappy Osc.

>UR) The key error in your idea is the assumption that every 100 
positive slopes
of your
100 Hz is identical with the start of a new second, which is wrong when 
you look
at it at
a second to second base.
Correct that my assumption was that every 100 pulses gives a one second 
pulse at
the
same location.You are incorrect that when this is not true, it is a key 
error in
my idea.
I did see that the 100Hz pulse that comes out at about the time as the 
1Hz
sawtooth
correction is updated seems to have the same amount of phase error as 
reported
for
the 1 Hz, best I could tell. I do know it is sometimes true, I'll check 
that out
better and
verify that it is not always true on my unit. Thanks for the 
information.
BUT, NO matter, because the max jitter error of around 100ns is the 
same in both
of
the 100Hz and the 1 Hz signal, and the 100Hz error is nonaccumative.
That is when I average 100 points each with an uncertainty of 100ns I 
get at
least the
Square root of 100 better resolution If they where truly random, which 
they are
not,
they have the same basic ramp type phase response as the 1 Hz sawtooth, 
just
much faster
so averaging works much better than if they where random.
What I have found is that the net effect is for the most part that 
averaging 100
100Hz
signals will give about the same error result as averaging 100 One 
second
pulses.
If you want to proof it to yourself use a digital scope with an average 
function
and look
at the results. (there are some rare exceptions, I skip over for now)

For another example, consider what the results would be if you just 
used every
100th 1 second pulse. You'd end up with 100ns uncertainty in 100 
seconds rather
the under 10 ns you get by averaging 100 1 second pulses (most of the 
time).

UR) What is true is that the MEAN frequency of the 100 Hz is locked to 
the GPS
and that is why your fast PLL works as well as James Miller's.
What I tried to state is that the 100Hz is fast enough to make a simple 
analog
PPL,
something that is not very easy to do with the 1 Hz signals.
Thanks for the name, I'll check more on how he is doing his simple GPS 
tracker.
It looks like he is using the 10KHz output of the Jupiter GPS.
Unfortunately my oncore does not have a 10KHz output.

Thanks,
Warren

***************************
James Miller, G3RUH, also uses the 100 Hz signal. So it's neither
specifically new nor the philosopher's stone that you may perhaps
believe to have found. The PPS and the 100 Hz signal come from the SAME
oscillator. The jitter in the PPS comes from the fact that the receiver
logic decides WHICH slope of the oscillator signal comes next close to
the TRUE point of time where the PPS should be generated. The key error
in your idea is the assumption that every 100 positive slopes of your
100 Hz is identical with the start of a new second, which is wrong when
you look at it at a second to second base. What is true is that the MEAN
frequency of the 100 Hz is locked to the GPS and that is why your fast
pll works as well as James Miller's.

Best regards
Ulrich Bangert
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