[time-nuts] Symmetricom SGC-1500

[Julien Goodwin]

Can anyone from Symmetricom/Microsemi help me with a firmware image for
an SGC-1500 for personal use?

I picked this thing up on eBay over a year ago, but only just got around
to getting the needed serial adapter bits to talk to it (should anyone
else need it, it's rolled from the standard Cisco convention, and 115200
8N1).

It seems like this unit must have been running some form of experimental
image based on the variety of boot errors it has. I tried the default
password I could find (admin/symmetricom) which let me log in but then
kicked me right back out as it couldn't find the shell.

Relevant version strings from the boot logs:
Linux version 2.6.32.46.cge (r...@cbuf15.symmetricom.com) (gcc version
4.3.3 (Cavium Networks Version: 2_1_0 build 110) ) #5 SMP PREEMPT Tue
Mar 12 14:57:59 MDT 2013

MontaVista Linux CGE 6 .dev-snapshot-20120201 SGC-1500 console
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Dan Rae]

On 9/21/2016 9:01 AM, David C. Partridge wrote:

Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over here 
in the UK PN measurement kit is a bit thin on the ground too.

So I looked at  but 
that seemed a little thin on details.  Or were you referring to something else?


The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm

as a pdf under link: "Low noise amplifier for Phase Noise measurements"
or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf

Pretty much all there, but the FET is hard to find now.

Dan
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Dan Rae]

On 9/21/2016 8:01 AM, David C. Partridge wrote:

Looks like all I've managed to do is measure the baseline noise of the 
analyser.  Ho-hum looks like I need something a *lot* quieter to do these 
measurements.

Indeed Dave, yes.  I made the same mistake a few years ago when I tried 
to compare the results of three different DDS clocks on the output of my 
homebrew transceiver DDS LO using a 3585A spectrum analyser and John's 
program.  It took me a while to figure out why they were identical and 
then the penny dropped that I was just measuring the 3585A...


The plot of the three thunderbolts I sent before using my -hp- phase 
noise system is interesting in that the white plot was from the Tbolt I 
keep on the bench to run all the stuff there, and it uses the switch 
mode power supply that came with the TAPR ones, built into an Extron 
distribution amp case.  All the spurs that are shown with dotted lines 
aren't all spurious, most are probably real.  The other two are from 
units with linear supplies and are significantly improved.


Most older phase noise systems use some kind of low noise oscillator for 
reference, mixing the signal under test down to AF and going from there 
with low noise amps and then the actual measurement. Wenzel has a very 
good application note describing a system that can be copied in the home 
lab.


I attach a plot of my -hp- 3048A system noise floor showing what levels 
can be achieved with twenty year old technology.  The spurs the system 
shows dotted may not be real.  The modern system John Miles designed can 
no doubt do better and in about one hundredth of the volume, but is a 
little more expensive :^)


Dan





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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over here 
in the UK PN measurement kit is a bit thin on the ground too.

So I looked at  but 
that seemed a little thin on details.  Or were you referring to something else?

Dave


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Re: [time-nuts] FS: Spectracom 8140 frequency distribution amps

[IEEE]

Hello Joe!

How about 100 for them?

Thanks,
David Jensen
W8PDP

> On Sep 20, 2016, at 8:55 PM, Joseph Gray  wrote:
> 
> More downsizing.
> 
> One unit works 100% (I have been using it for years). It includes the
> 5 MHz option board, which I have disabled, for 10 MHz use. I have also
> disabled the DC voltage on the four outputs, as I wasn't using the
> external Taps. These functions can be very easily restored if you need
> them. The second unit partially works. I haven't taken the time to see
> what the problem is.
> 
> $150 OBO for both, plus shipping/insurance. Somewhere I have the PDF
> manual with schematics.
> 
> Joe Gray
> W5JG
> 
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Looks like all I've managed to do is measure the baseline noise of the 
analyser.  Ho-hum looks like I need something a *lot* quieter to do these 
measurements.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 18 September 2016 13:43
To: 'Bruce Griffiths'; 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
 wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Attila Kinali]

On Wed, 21 Sep 2016 09:16:18 -0700
Dan Rae  wrote:

> On 9/21/2016 9:01 AM, David C. Partridge wrote:
> > Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over 
> > here in the UK PN measurement kit is a bit thin on the ground too.
> >
> > So I looked at  
> > but that seemed a little thin on details.  Or were you referring to 
> > something else?
> >
> The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm
> 
> as a pdf under link: "Low noise amplifier for Phase Noise measurements"
> or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf
> 
> Pretty much all there, but the FET is hard to find now.

If you want to build such an amplifier, then the first stage (aka the
jFET input and the first opamp) is the critical component. There are
other, more modern descriptions for this kind of application, in case
you don't want to just replace the jFET by one if its modern cousins.

One well known is AN124[1] and it's more current cousin AN159[2].
For the later, Bruce commented that an jFET input stage would
probably be more quiet. Gerhard Hoffman has designed a similar
system[3] that uses a couple of paralel low noise opamps instead
of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
these would need to be adapted to imporve thier frequency response
up to 10MHz (or actually a bit higher), but then the input stage
gets also a bit simpler as you don't need the huge capacitors anymore.

I also recommend a look at [4] which lists a couple of issues with jFET
input stages for opamps and how to get around them.

Attila Kinali


[1] "775 Nanovolt Noise Measurement for A Low Noise Voltage Reference",
by Jim Williams, Linear AN124, 2009

[2] "Measuring 2nV/sqrt(Hz) Noise and 120dB Supply Rejection
on Linear Regulators", by Todd Owen and Amit Patel, Linear AN159, 2016

[3] "A 220 pV/sqrt(Hz) low noise preamplifier", by Gerhard Hoffman, 2014
http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf

[4] "Some Tips on Making a FETching Discrete Amplifier", by George Alexandrov
and Nathan Carter, Analog Dialog 47-10, 2013
http://www.analog.com/library/analogdialogue/archives/47-10/discrete_amplifier.html


-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Chris Caudle]

On Wed, September 21, 2016 1:59 pm, Attila Kinali wrote:
> On Wed, 21 Sep 2016 09:16:18 -0700
  > Dan Rae  wrote:
  >> Pretty much all there, but the FET is hard to find now.
>
> If you want to build such an amplifier, then the first stage (aka the
> jFET input and the first opamp) is the critical component. There are
> other, more modern descriptions for this kind of application, in case
> you don't want to just replace the jFET by one if its modern cousins.

If you do want to just substitute newer parts into the same style design,
you should be able to get Linear Systems jfets.  They are not as quiet,
but much lower capacitance, so you could put more in parallel to get
reduced noise.

http://linearsystems.com/products_details.php?pr=jfet-amplifiers--duals_id=65

-- 
Chris Caudle


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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Gerhard Hoffmann]

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths:

For the later, Bruce commented that an jFET input stage would

probably be more quiet. Gerhard Hoffman has designed a similar

I must insist in my second "n" Hoffmann   :-)

system[3] that uses a couple of paralel low noise opamps instead
of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
these would need to be adapted to imporve thier frequency response
up to 10MHz (or actually a bit higher), but then the input stage
gets also a bit simpler as you don't need the huge capacitors anymore.


The ADA4898 has ft= 50 MHz, so that will be hard. It already takes some 
cascoding

to get to 2 MHz with the new FET amp.

Another issue is the requirement to trim the current sink for low output
offset. If one takes advantage of the fact that the PLL imposes a low
frequency cutoff to the PN measurements, the amplifier input   can be AC
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

Using a single ended input stage is significantly quieter than using a
differential pair.

Paralleled BF862's can be substituted for the input JFET.


Hi, Bruce and Attila (and ...),

the JFET version of my preamp is making progress. It supports either upto 16
BF862 or 2 pairs of Interfet IF3602. Upper bandwidth limit will be 2 MHz if
it runs like the simulation. There is also a low gain DC output for the PLL.

< 
https://www.flickr.com/photos/137684711@N07/29193737144/in/dateposted-public/ 
>


One is populated with BF862, the other with Interfet. The 3rd will be 
populated

according to the outcome of the first tests, so that I have 2 equal ones for
X correlation. There will be some leftover boards available, but not to 
put them

into the drawer.

Soldered them last weekend, debug them on the next :-)
I expect 170 pV/rt Hz at least for the Interfet version. That is 
probably pearls before

swine after a ring mixer, but then we are nuts.

Attila, you are just half an hour of driving away, at least during the 
weekend!


regards, Gerhard




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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Gerhard Hoffmann]

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths:

Another issue is the requirement to trim the current sink for low output
offset.


And _that_ FET is made from Unobtainium.

If one takes advantage of the fact that the PLL imposes a low
frequency cutoff to the PN measurements, the amplifier input   can be AC
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

That's what I did. Original Burr-Brown opa2134, time to use them up..

Paralleled BF862's can be substituted for the input JFET.


Yep!
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Re: [time-nuts] Lucent RFTFm-II-XO

[Chris Waldrup]

Hi,

The USB to RS422 adapter arrived.  According to the online manual for the 
adapter, the RS422 signals I'm looking for are:
Send A+
Send B-
Receive A+
Receive B-

Is there a pinout posted somewhere  for the Lucent box RS422 D sub 9 connector?

Thank you. 

Chris
KD4PBJ

> On Sep 14, 2016, at 06:12, Bob Camp  wrote:
> 
> Hi
> 
> These days, a RS-422 to USB adapter is a sub $20 item, even from a “name 
> brand” outfit with real
> drivers. . If you shop a bit, you can get some dirt cheap USB to 422 adapters 
> at the risk of having 
> issues with the drivers (now or down the road). 
> 
> Bob
> 
>> On Sep 13, 2016, at 11:44 PM, Chris Waldrup  wrote:
>> 
>> Hi,
>> 
>> Regarding the Lucent box- I wanted to let everyone know that once it locked 
>> to satellites, I have a 10 MHz out. 
>> The output was a square wave with some ringing, but I built a three element 
>> low pass filter and now I have a really nice 10 MHz sine wave. 
>> Thanks to all!
>> 
>> Last question I see it has a RS-422 output on one of the connectors. If 
>> I build or buy a 422 to 232 converter can I expect to be able to view the 
>> unit's data output with something like Lady Heather or Tboltmon? Or at least 
>> see an output with Hyperterminal?
>> 
>> Thank you. 
>> 
>> Chris
>> KD4PBJ
>> 
>>> On Sep 6, 2016, at 16:42, Bob Camp  wrote:
>>> 
>>> Hi
>>> 
>>> One might *think* a redundant system would work fine with the plug yanked. 
>>> In this case …. nope. It needs to have a dummy connector on it to get the 
>>> device
>>> running. I agree that this is an “interesting” way to do it. Regardless of 
>>> that, they
>>> did the units need the signals from the other box (or fake signals)  before 
>>> they 
>>> will do useful stuff.
>>> 
>>> Bob
>>> 
>>> 
 On Sep 5, 2016, at 10:22 PM, Bill Hawkins  wrote:
 
 Fake connections? Isn't a redundant system supposed to allow one box to
 be disconnected?
 
 Bill Hawkins 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
 Camp
 Sent: Monday, September 05, 2016 8:20 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Lucent RFTFm-II-XO
 
 Hi
 
 If you only have one box, you need to be sure the "fake" connections on
 the interconnect are correct. If they are not, you will not get it to
 operate correctly. 
 
 There also is a survey process if you have not had it running in your
 location before. That could take a few hours to a few days depending on
 your antenna.
 
 Bob
 
 
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 To unsubscribe, go to 
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>>> 
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[Bruce Griffiths]

On Wednesday, September 21, 2016 08:59:18 PM Attila Kinali wrote:
> On Wed, 21 Sep 2016 09:16:18 -0700
> 
> Dan Rae  wrote:
> > On 9/21/2016 9:01 AM, David C. Partridge wrote:
> > > Yes,  I fear a timepod is a bit out of my budget (I can dream tho'). 
> > > Over here in the UK PN measurement kit is a bit thin on the ground 
too.
> > > 
> > > So I looked at 

> > > but that seemed a little thin on details.  Or were you referring to
> > > something else?> 
> > The Wenzel note is at: http://www.wenzel.com/documents/circuits1.htm
> > 
> > as a pdf under link: "Low noise amplifier for Phase Noise 
measurements"
> > or try:  www.wenzel.com/wp-content/uploads/lowamp.pdf
> > 
> > Pretty much all there, but the FET is hard to find now.
> 
> If you want to build such an amplifier, then the first stage (aka the
> jFET input and the first opamp) is the critical component. There are
> other, more modern descriptions for this kind of application, in case
> you don't want to just replace the jFET by one if its modern cousins.
> 
> One well known is AN124[1] and it's more current cousin AN159[2].
> For the later, Bruce commented that an jFET input stage would
> probably be more quiet. Gerhard Hoffman has designed a similar
> system[3] that uses a couple of paralel low noise opamps instead
> of a jfet stage and claims a noise floor of 220pV/sqrt(Hz). All of
> these would need to be adapted to imporve thier frequency response
> up to 10MHz (or actually a bit higher), but then the input stage
> gets also a bit simpler as you don't need the huge capacitors anymore.
> 
> I also recommend a look at [4] which lists a couple of issues with jFET
> input stages for opamps and how to get around them.
> 
>   Attila Kinali
> 
> 
> [1] "775 Nanovolt Noise Measurement for A Low Noise Voltage 
Reference",
> by Jim Williams, Linear AN124, 2009
> 
> [2] "Measuring 2nV/sqrt(Hz) Noise and 120dB Supply Rejection
> on Linear Regulators", by Todd Owen and Amit Patel, Linear AN159, 2016
> 
> [3] "A 220 pV/sqrt(Hz) low noise preamplifier", by Gerhard Hoffman, 2014
> http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf
> 
> [4] "Some Tips on Making a FETching Discrete Amplifier", by George
> Alexandrov and Nathan Carter, Analog Dialog 47-10, 2013
> 
http://www.analog.com/library/analogdialogue/archives/47-10/discrete_ampl
ifi
> er.html

2sk369BL are still available from:
http://www.ampslab.com/trans_2sk369.htm

I obtained some from them, they met the noise specs so are probably not 
counterfeit.

One issue with the Wenzel preamp is that it has poor PSRR.
This can easily be improved substantially by redesigning the bias circuitry 
for the opamp noninverting input.

Another issue is the requirement to trim the current sink for low output 
offset. If one takes advantage of the fact that the PLL imposes a low 
frequency cutoff to the PN measurements, the amplifier input   can be AC 
coupled, allowing dc bias feedback to be applied to the input device gate.
Use a parallel dc coupled JFET input opamp for the PLL

Using a single ended input stage is significantly quieter than using a 
differential pair.

Paralleled BF862's can be substituted for the input JFET.

Bruce
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Re: [time-nuts] Inside of FT1200-100

[Ed Palmer]

I had to tear apart an FTS1200 that had a broken Dewar.  I had trouble 
getting it apart because that red rubber sheet was bonded to the glass 
of the Dewar and the oven.  Since the Dewar was smashed anyway, I was 
able to dig the oscillator out by smashing the Dewar even more.


You might be able to slide something like a feeler guage down between 
the oven and the rubber blanket to break the oscillator free.  The oven 
on mine is a plain metal cylinder.  This way, the rubber sheet should 
protect the Dewar from your feeler guage.  On mine, the mounting bolts 
for the 2N3792 transistor both have ground lugs.  I think I see them on 
yours.  You could hook something through the ground lugs and use that to 
pull the oscillator out of the rubber sheet and then remove the sheet 
later.


Ed

On 2016-09-21 9:46 AM, time-nuts-requ...@febo.com wrote:

Date: Tue, 20 Sep 2016 16:42:40 -0700
From: Christopher Hoover
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Inside of FT1200-100
Message-ID: