[time-nuts] GPSDO using 100Hz

[WarrenS]

Ernie

I do have to agree that the James Miller unit is about as simple as you can get. His BIG advantages is the use of 10KHz to lock on.
If the want to use the Jupiter GPS board, Miller's circuit is the way to go for SIMPLE.
Bob Q has the same basic circuit configuration running off the 100Hz signal. It is listed in  "June 08. "[time-nuts] Simple GPS 10 MHz frequency standard"
Bob's circuit has a lot more bills and whistles than Millers to tell when it is locked etc, but the extra bills he added does not effect the performance, for the most part, once it is locked. All else being equal the 100Hz XOR is not going to be as good as the 10KHz, although with about 100 times more care in the analog circuits to control noise, which Bob's seems to have, and with the right RC's they could be pretty similar performance.

What I am doing is somewhat different in that I wanted mine to work with my 100 Hz Oncore receiver and I do not use a XOR phase detector because of its very low phase low gain at 100 Hz.

Thanks for the response,
Warren

**************
----- Original Message ----- 
From: <ernieperes at aol.com>
To: <time-nuts at febo.com>
Sent: Monday, November 24, 2008 5:13 AM
Subject: Re: [time-nuts] GPSDO using 100Hz


> 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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