Re: [time-nuts] More on SiLabs 5340

[Magnus Danielson]

Hi,

On 01/31/2018 04:27 AM, John Miles wrote:
> 
>> -Original Message-
>> There is a small detail that puzzles me: the ADEV for the internal
>> reference 10MHz and 30MHz bends upwards at tau greater than 0.1s.
>> Shouldn't that be visible by a change in slope in the phase noise
>> plot at ~10Hz as well?
>>
>>  Attila Kinali
> 
> 
> Linear drift (which is what's happening here) has a bigger effect on the 
> overall gestalt of an ADEV plot than it will on a phase noise plot.  This is 
> because long-term drift looks similar to DC offset or noise at extremely low 
> frequencies, both of which are attenuated by an HPF stage prior to each FFT 
> segment.  But ADEV doesn't benefit from DC removal, and since it doesn't 
> converge in the presence of drift, you get the usual upturn in the trace at 
> increasing taus. 

As ADEV is defined, it is bound to be captured by linear, and higher
terms, drift. FFT is not directly, but on the other hand sensitive to DC
shifts that usually is handled by the window function, which also helps
to work on spectral purity. None of the measures is very perfect so they
need to be handled with care.

> When you see a highly-elevated noise trace at low offset frequencies, it's 
> also a good idea to check for glitches in the 'f' measurement view, although 
> in this case the L(f) spectrum is very typical of these sorts of parts. 

Glitches can totally ruin an ADEV.

Cheers,
Magnus
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Re: [time-nuts] More on SiLabs 5340

[John Miles]

> -Original Message-
> There is a small detail that puzzles me: the ADEV for the internal
> reference 10MHz and 30MHz bends upwards at tau greater than 0.1s.
> Shouldn't that be visible by a change in slope in the phase noise
> plot at ~10Hz as well?
> 
>   Attila Kinali


Linear drift (which is what's happening here) has a bigger effect on the 
overall gestalt of an ADEV plot than it will on a phase noise plot.  This is 
because long-term drift looks similar to DC offset or noise at extremely low 
frequencies, both of which are attenuated by an HPF stage prior to each FFT 
segment.  But ADEV doesn't benefit from DC removal, and since it doesn't 
converge in the presence of drift, you get the usual upturn in the trace at 
increasing taus. 

When you see a highly-elevated noise trace at low offset frequencies, it's also 
a good idea to check for glitches in the 'f' measurement view, although in this 
case the L(f) spectrum is very typical of these sorts of parts. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Sick Trimble TBolt

[Bruce Griffiths]

At least one model used a comparatively noisy wideband unity gain analog buffer 
IC.
Without the buffer the OCXO PN was is lower.

Bruce 
> On 31 January 2018 at 12:41 Chris Caudle  wrote:
> 
> 
> > What are the markings of the devices close to the BNC connector?
> 
> Just a guess based on some previous comments from Bob, you are probably
> looking for a logic gate, probably with an LC filter on the output.  Could
> also be some kind of MMIC device, but gate with a filter seems like a good
> possibility.
> Probably SOIC device, shouldn't be too hard to replace.
> 
> -- 
> Chris Caudle
> 
> 
> 
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Re: [time-nuts] Sick Trimble TBolt

[Chris Caudle]

> What are the markings of the devices close to the BNC connector?

Just a guess based on some previous comments from Bob, you are probably
looking for a logic gate, probably with an LC filter on the output.  Could
also be some kind of MMIC device, but gate with a filter seems like a good
possibility.
Probably SOIC device, shouldn't be too hard to replace.

-- 
Chris Caudle



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Re: [time-nuts] Sick Trimble TBolt

[Chris Caudle]

On Tue, January 30, 2018 11:33 am, Richard Solomon wrote:
> I noticed a spot that looks like it takes a PC mount SMA.

Others have noted that the PCB appears to support multiple different
footprint oscillators or input of an external oscillator.

> Looking at the center pin, it looks like the output of the TCXO.
> I plan to run a small coax from that to the BNC output connector.
> Any thoughts or comments ?

If the output buffer is not operating properly, then there is a high
likelihood the broken output buffer will just drag down the output of the
OCXO, which will prevent the entire device from operating. Even with the
buffer disconnected you risk disrupting the operation of the GPS receiver
when you connect and disconnect loads to the BNC connector (if the GPS
receiver even keeps operating properly with a 50 Ohm load directly on the
oscillator output).

What are the markings of the devices close to the BNC connector?  Don't
forget to check the bottom of the PCB, there are a few devices there as
well on some models, but I don't know if the layout is the same on all
revisions.

-- 
Chris Caudle


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[time-nuts] Sick Trimble TBolt

[Richard Solomon]

Without any adequate documentation, I decided to probe around
the board. I noticed a spot that looks like it takes a PC mount SMA.

Looking at the center pin, it looks like the output of the TCXO.

I plan to run a small coax from that to the BNC output connector.

Perhaps it will make this thing usable again. Beats parting it out.

Any thoughts or comments ?

Thanks, Dick, W1KSZ

Sent from Outlook
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Re: [time-nuts] Microsemi 3120A sold on eBay

[Lester Veenstra]

They are becoming the semiconductor/timing MFJ

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
les...@veenstras.com

Physical and US Postal Addresses
5 Shrine Club Drive (Physical)
HC84 452 Stable Ln (RFD USPS Mail)
Keyser WV 26726
GPS: 39.336826 N  78.982287 W (Google)
GPS: 39.33682 N  78.9823741 W (GPSDO)


Telephones:
Home: +1-304-289-6057
US cell+1-304-790-9192 
Jamaica cell:   +1-876-456-8898 
 


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: Sunday, January 28, 2018 9:58 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Microsemi 3120A sold on eBay

Hi

There’s a cluster of time and frequency outfits up in the Salem area. Some have 
been there for a *long* time indeed. The EG / Perkin Elmer Rubidium guys are 
one that comes to mind.  MTI is a bit further north, but still in the same side 
of the Boston urban sprawl. 

Bob

> On Jan 27, 2018, at 10:10 PM, John Allen  wrote:
> 
> It is interesting to note that the seller is in Salem, MA, a few miles south 
> of Microsemi in Beverly, MA.
> 
> PS: Here is a list of the many acquisitions they have made:
> https://www.microsemi.com/company/acquisitions
> 
> John K1AE
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John 
> Miles
> Sent: Saturday, January 27, 2018 6:49 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] Microsemi 3120A sold on eBay
> 
> They're essentially the same as the original TimePod 5330A specs  ( 
> http://www.miles.io/TimePod_5330A_user_manual.pdf page 11).  The 3120A 
> doesn't display noise at offsets below 1 Hz, though, while the 5330A went 
> down to 0.01 Hz.  Also, some of the TimePod features are "added-value" 
> software options in the 3120A, but it's not clear if this unit came with any 
> of the license keys.  
> 
> The final selling price seems fairly reasonable considering the sparse 
> details provided by the seller.  If someone on the list bought it and it 
> doesn't have the software CD, drop me a note offline and I'll hook you up.
> 
> -- john, KE5FX
> Miles Design LLC
> 
>> What are the specs ? 73 de N1UL
>> 
>> Sent from my iPhone
>> 
>>> On Jan 27, 2018, at 5:38 PM, John Miles  wrote:
>>> 
>>> So, who's the lucky winner?  Anyone on here?  That's the first one 
>>> of these I've seen in the "secondary market," so to speak.
>>> 
>>> 
>>> 
>>> https://www.ebay.com/itm/332531180078
>>> 
> 
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Re: [time-nuts] More on SiLabs 5340

[Attila Kinali]

Moin,

On Mon, 29 Jan 2018 15:38:33 -0500
John Ackermann N8UR  wrote:

> 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.

There is a small detail that puzzles me: the ADEV for the internal
reference 10MHz and 30MHz bends upwards at tau greater than 0.1s.
Shouldn't that be visible by a change in slope in the phase noise
plot at ~10Hz as well?

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] UK government study on: Satellite-derived Time and Position - Critical Dependencies

[David J Taylor via time-nuts]

UK government study on: Satellite-derived Time and Position - Critical 
Dependencies


 
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/676675/satellite-derived-time-and-position-blackett-review.pdf

Seems quite comprehensive, and may be of interest to GNSS users.  1.6 MB and 
86 pages.


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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