Re: [time-nuts] More on SiLabs 5340

[jimlux]

On 1/29/18 3:37 PM, Mark Goldberg wrote:

Reference my earlier postings titled "SI532X Chips Close In Spurs (Somewhat
Long)". There are many sets of register values that will get you the same
output frequency and the clock builder may not give you an optimal set for
phase noise and spurs. I created a spreadsheet to calculate other sets of
values and chose one that worked the best. I just did it through trial and
error of the different sets of values I came up with until I found one with
low spurs.




We've experienced that here with other PLL chips - For the ADF4108 
integer-N PLL, sometimes there's a big difference between R odd and R 
even (the R is the reference divisor in the fout = fin * (M*B+A)/R


So you wind up fooling around with various combinations of A, B, and R 
to get the spurs where you want them (or, more commonly, to move them 
from where you don't want them)


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Re: [time-nuts] More on SiLabs 5340

[Mark Goldberg]

Reference my earlier postings titled "SI532X Chips Close In Spurs (Somewhat
Long)". There are many sets of register values that will get you the same
output frequency and the clock builder may not give you an optimal set for
phase noise and spurs. I created a spreadsheet to calculate other sets of
values and chose one that worked the best. I just did it through trial and
error of the different sets of values I came up with until I found one with
low spurs.

73,

Mark
W7MLG

On Mon, Jan 29, 2018 at 4:16 PM, John Ackermann N8UR  wrote:

> On 01/29/2018 04:54 PM, Chris Caudle wrote:
>
>> On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:
>>
>>> The close-in phase noise is quite amazing, but the floor is much worse
>>> than in free-run mode.
>>>
>>
>> That phase noise plot doesn't look quite right, what PLL bandwidth did you
>> set?
>>
>
> Sorry for the earlier null reply.  I just used the settings that the
> ClockBuilder software came up with (which IIRC don't offer any choices
> about loop bandwidth in the "wizard").  I haven't yet dug into the register
> options, but I'm sure that there are ways to optimize.
>
> John
>
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Re: [time-nuts] GPS Jamming

[Gary E. Miller]

Yo Gary!

On Fri, 26 Jan 2018 07:57:02 -0700
Gary Neilson  wrote:

> Don't know if this has be posted before or not. Also don't know if
> this will affect timing info.

I am a commercial pilot in Bend, OR.  There is a lot of 'GPS testing'
going on in Fallon, NV.  About every month I recieve a notice about
specific times that 'GPS may be unavailable' near Fallon.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin


pgpGemeaWkuFh.pgp
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Re: [time-nuts] More on SiLabs 5340

[John Ackermann N8UR]

On 01/29/2018 04:54 PM, Chris Caudle wrote:

On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:

The close-in phase noise is quite amazing, but the floor is much worse
than in free-run mode.


That phase noise plot doesn't look quite right, what PLL bandwidth did you
set?


Sorry for the earlier null reply.  I just used the settings that the 
ClockBuilder software came up with (which IIRC don't offer any choices 
about loop bandwidth in the "wizard").  I haven't yet dug into the 
register options, but I'm sure that there are ways to optimize.


John
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[time-nuts] SA22.c (and other) interface boards

[Mark Sims]

I got in my prototypes for the SA22.c interface board from OSHPARK.   It seems 
to be working well.   It has a square to sine wave filter (thanks Charles!) 
since the SA22 only outputs an ACMOS square wave.  There is tiny but of fuzz on 
the peaks of the sine wave.   There is a jumper for routing the ACMOS signal to 
the connector board,  but doing that distorts the sine wave (the X72 does the 
same thing, Symmeticom engineer said not to use both outputs.

I also did a board for the LPFRS/LPRO/OCXOs and just finished a layout for the 
EG TS-RFS rubidium.  These boards have a PICDIV for doing a 1PPS output and a 
PICPET for implementing a 100 ns res timestamping counter.I have modified 
the connector board to support SMA connectors and 24V devices.

 I have the SRO100/SRO70 interface boards in and assembled.

Board should be going to China PCB fab house this week.
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Re: [time-nuts] More on SiLabs 5340

[John Ackermann N8UR]

On Jan 29, 2018, 4:54 PM, at 4:54 PM, Chris Caudle  
wrote:
>On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:
>> The close-in phase noise is quite amazing, but the floor is much
>worse
>> than in free-run mode.
>
>That phase noise plot doesn't look quite right, what PLL bandwidth did
>you
>set?
>
>-- 
>Chris Caudle
>
>
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Re: [time-nuts] More on SiLabs 5340

[Chris Caudle]

On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:
> The close-in phase noise is quite amazing, but the floor is much worse
> than in free-run mode.

That phase noise plot doesn't look quite right, what PLL bandwidth did you
set?

-- 
Chris Caudle


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Re: [time-nuts] More on SiLabs 5340

[Chris Caudle]

On Mon, January 29, 2018 2:38 pm, John Ackermann N8UR wrote:
> to do, though, was feed 10 MHz into the "Input 0" port which apparently
> disciplines the free-running crystal.

It doesn't discipline the crystal oscillator, the crystal oscillator is
multiplied up and used as the clock to run a DDS block.  The 10MHz signal
you input is the reference input to a digital PLL, and the output of the
PLL modifies the tuning word of the DDS.

In free run mode it works similarly, but the tuning word never changes,
the DDS control value is chosen based on assuming that the DDS clock is
running exactly at nominal frequency.

-- 
Chris Caudle


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Re: [time-nuts] More on SiLabs 5340

[Bob kb8tq]

Hi

There may be “tweaks” to get the noise shaping working better on the 10 MHz 
input. Some PLL
chips have pre-multipliers for the reference to improve things…. the magic 
apparently works better
with a fast input …(and yes, there are good reasons why)

Bob

> On Jan 29, 2018, at 3:38 PM, John Ackermann N8UR  wrote:
> 
> I'm slowly learning how these ultra-low-jitter clock generators work. 
> Yesterday I posted some phase noise results in "free run" mode where the 48 
> MHz crystal on the evaluation board was the only reference.
> 
> Today I tried replacing the crystal with a 10 MHz input, and found that the 
> evaluation board requires surgery to support that.  What I was able to do, 
> though, was feed 10 MHz into the "Input 0" port which apparently disciplines 
> the free-running crystal.  I used a 10811A fed into a T2-Mini with divider 
> removed, so all it does is provide the Wenzel squaring circuit.  Results 
> attached, added to the plots from yesterday. Also attached is an ADEV plot 
> proving that the 10 MHz is in control.
> 
> The close-in phase noise is quite amazing, but the floor is much worse than 
> in free-run mode.  This was a very hay-wire experiment, so there are lots of 
> things that could be suboptimal.  It sure would be nice to get the best of 
> both those plots!
> 
> John
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Re: [time-nuts] CSAC Project(was CSAC purchase)

[Bob kb8tq]

Hi

Questions are good, it’s how you figure things out. We’re talking about a 
“practical” timing device design. It’s not as crazy a topic as it might seem. 

Some basic math: 

You get to a million seconds at about 11.6 days. A millisecond error over that
period is one ppb. If you are off 1 ppb at T=0 and stay there, you will be off
by 1 ms. If you drift so you are off by 1 ppb at the end, you will be off by 
less 
than 1 ms.

At some point, you do need “rough numbers” to work out what you are going to do.

Holding a few microseconds (not milliseconds, we just jumped a factor of a 
thousand) 
on a GPS based wall clock / watch is quite practical, even with poor GPS access 
( = crummy
antenna).  With a reasonable antenna 100’s of ns are very practical, even with 
a 
cheap GPS module. 

The practical question would be: What am I getting from the CSAC? One basic 
answer
might be “holdover” at less than 1 us / day. Another basic answer might be 
autonomous 
operation in a location where GPS simply isn’t available. 

Lots to think about.

Bob 

> On Jan 29, 2018, at 12:44 PM, Ronald Held  wrote:
> 
> Bob;
>  I see what you are saying.  I will wait until I get the chips d more
> before asking more questions.
> Ronald
> 
> Hi
> 
> As mentioned multiple times in the archives. As you get into the single digit
> milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off
> and one that is 1 ms off are both “good enough” if you are looking at it with 
> a
> normal eyeball.
> 
> From a design standpoint 1 ms / day / week is *way* different that 1 ns over 
> the
> same sort of period. Design constraints *do* make a big difference.
> It’s important
> in any project to get them sorted early.
> 
> If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t
> going to even get into the roundoff error. You *will* need the GPS gizmo to
> keep the CSAC calibrated. It is only a question of how often the beast gets
> used.
> 
> Bob
> 
> On 1/29/18, Ronald Held  wrote:
>> 
>> 
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Re: [time-nuts] CSAC Project(was CSAC purchase)

[Ronald Held]

Bob;
  I see what you are saying.  I will wait until I get the chips d more
before asking more questions.
 Ronald

Hi

As mentioned multiple times in the archives. As you get into the single digit
milliseconds, the human eye simply can’t keep up. A watch that is 1 ns off
and one that is 1 ms off are both “good enough” if you are looking at it with a
normal eyeball.

>From a design standpoint 1 ms / day / week is *way* different that 1 ns over 
>the
same sort of period. Design constraints *do* make a big difference.
It’s important
in any project to get them sorted early.

If you are spending $5K on a CSAC, tossing in another $100 on a GPS isn’t
going to even get into the roundoff error. You *will* need the GPS gizmo to
keep the CSAC calibrated. It is only a question of how often the beast gets
used.

Bob

On 1/29/18, Ronald Held  wrote:
>
>
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Re: [time-nuts] CSAC Project(was CSAC purchase)

[Ronald Held]

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Re: [time-nuts] GPS Jamming

[Wes]

This has been going on a long time.

http://defense-update.com/products/g/gps-ajr.htm

I was involved with testing this in the field years earlier.

Wes

On 1/26/2018 7:57 AM, Gary Neilson wrote:
Don't know if this has be posted before or not. Also don't know if this will 
affect timing info.


GPS Jamming 



I am on the very edge of their coverage map.

Gary

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Re: [time-nuts] GPS Jamming

[David C. Partridge]

I thank Adrian was being sarcastic :)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani
Sent: 29 January 2018 10:00
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Jamming

Wasn't the selective availability an accuracy degradation system?

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Re: [time-nuts] GPS Jamming

[Azelio Boriani]

Wasn't the selective availability an accuracy degradation system?

On Mon, Jan 29, 2018 at 10:55 AM, Adrian Godwin  wrote:
> What a pity nobody thought to include an accuracy degradation system into
> GPS itself, for use when you don't want the enemy to benefit from it.
>
> And how odd to show off your secret jamming technology in a major scheduled
> exercise, so the Bad Guys can study it.
>
>
> On Fri, Jan 26, 2018 at 2:57 PM, Gary Neilson  wrote:
>
>> Don't know if this has be posted before or not. Also don't know if this
>> will affect timing info.
>>
>> GPS Jamming > gps-in-the-western-u-s-for-largest-ever-red-flag-air-war-exercise>
>>
>> I am on the very edge of their coverage map.
>>
>> Gary
>>
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Re: [time-nuts] GPS Jamming

[Adrian Godwin]

What a pity nobody thought to include an accuracy degradation system into
GPS itself, for use when you don't want the enemy to benefit from it.

And how odd to show off your secret jamming technology in a major scheduled
exercise, so the Bad Guys can study it.


On Fri, Jan 26, 2018 at 2:57 PM, Gary Neilson  wrote:

> Don't know if this has be posted before or not. Also don't know if this
> will affect timing info.
>
> GPS Jamming  gps-in-the-western-u-s-for-largest-ever-red-flag-air-war-exercise>
>
> I am on the very edge of their coverage map.
>
> Gary
>
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[time-nuts] GPS Jamming

[Gary Neilson]

Don't know if this has be posted before or not. Also don't know if this 
will affect timing info.


GPS Jamming 



I am on the very edge of their coverage map.

Gary

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