Re: [time-nuts] 32768 Hz from 10 MHz

[Dennis Ferguson]

On 3 Feb, 2012, at 14:15 , Orin Eman wrote:

> On Thu, Feb 2, 2012 at 7:16 PM, Hal Murray  wrote:
> 
>> 
>>> It's possible to use Bresenham with two integers 10,000,000 and 32,768
>> but I
>>> found no way to perform all the 24-bit calculations on an 8-bit PIC quick
>>> enough. Removing the GCD often helps but in this case the accumulator
>>> remains 3-bytes wide.
>> 
>>> To generate 32 kHz you have to toggle a pin and calculate if the next
>> toggle
>>> must be 38 or 39 instructions in the future; all the math must occur
>> within
>>> 37 instructions. That's why I came up with the binary leap year kind of
>>> algorithm; it's as close to math-less as you can get.
>> 
>> You missed the simple way.  Table lookup.  :)
>> 
>> The table is only 256 slots long.
>> 
>> That's toggling between 305 and 306 cycles.  If your CPU uses N clocks per
>> instruction, multiply the table size by N.
>> 
> 
> 
> 
> Well, I thought table lookup too, but I figured  a 2048 x 1 table.  Easily
> done with a rotating bit and 256 byte table.
> 
> 
> Assuming clocking a PIC at 10MHz, you have 2,500,000 instructions per
> second.  Since there was talk about time to the next toggle, we have
> 2,500,000/65536 instructions between toggles, ie 38.1470... instructions.
> The fraction turns out to be 301/2048, so you have to distribute 301 extra
> instructions over every 2048 half-periods of the 32768Hz waveform.

I only barely know the instruction set on those processors, but it seems
like it should be way easier than that.  You know it is going to be 38 or
39 instructions, so that only question is when it should be 39.  The value
of 250/65536 is 38.1470… in decimal, but in hex it is exactly 26.25a;
that is the 0x26 is 38 decimal while the fractional part is only 10 bits
long.  This means you should be able to compute when the extra cycle is
required by keeping a 16 bit accumulator to which the fractional part
0x25a0 is added at every change and executing the extra instruction when
there is a carry out of that. The seems straight forward.  If `lo' and `hi'
are the two halves of the accumulator then the working part of this becomes
something like (excusing my PIC assembler, which I mostly forget):

movl0xa0,w  // low byte of increment into w
add w,lo// add w to lo, may set carry
movl0x25,w  // high byte of increment into w
btfsc   3,0 // skip next if carry clear
add one,w   // increment w by one; I'm not sure how to do that
add w,hi// add w to hi, may set carry
// if carry set here need extra instruction.  Maybe this does it?
btfss   3,0 // skip if carry set
gotoblorp   // carry clear, don't execute next instruction
nop // the extra instruction
blorp:
// enough instructions more to make 38/39

Maybe someone who knows what they're doing can interpret that?

Dennis Ferguson
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Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders

[Azelio Boriani]

Yes, DLL not DDL I made a mistake. Actually it is not in my schedule to
make such a divisor, just for speculation. The main thought here is that,
as you pointed out, it can be done avoiding PLL and DLL.

On Fri, Feb 3, 2012 at 1:49 AM, Hal Murray  wrote:

>
> > OK for the PSOC example. At the moment I can try on a Spartan3 because I
> > already have a board with the OCXO. The Spartan3 has the so called DCM, a
> > digital clock generator that can multiply an input clock using its DDL
> > digital delay line.
>
> The original context was keeping wall clock time.  In that application,
> jitter on the 32 KHz clock isn't a problem.
>
> If I was hacking with a FPGA, I'd make a decimal addition module and chain
> 7
> of them together and see how fast it goes.  The idea is to avoid the DLLs,
> KISS.
>
> If it runs at 10 MHz (100 ns), I'd declare victory and try to see how well
> it
> works.  I'd probably divide by 32K and compare that with another handy PPS.
>
> If it doesn't run at 100 ns, I'd probably insert a pipeline FF in the carry
> chain, or as many as were needed.  It won't change the overall result, just
> delay the output signal by a clock cycle.
>
>
> If that worked, I might try to see how fast I could get it to run.  That's
> just for fun/ego.  The obvious target is 100 MHz which just adds one more
> decimal counter stage and probably several/many pipeline FFs.  That should
> cut the jitter from 100 ns peak-peak to 10 ns.  It won't change the overall
> frequency stability.
>
>
> --
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
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Re: [time-nuts] FE5680 missing PPS soln

[Rob Kimberley]

Mine was a green LED out of the junk box, but I did use 330R in series. 1k8
seems rather large.
I will probably put something between the 5680 and the LED later. I have a
bin full of old 74xx, so should be easy.

I've seen lots of threads about the 5680 and tweaks etc., but not much on
actually building them into anything.

I just built a very cheap dual unit (two 5680s bolted in). When I say cheap,
the only thing bought were the 5680s. The rest was out of the junk box.

The case is from an old Technics tape deck
Front panel is cut down and drilled from an old PC side panel.
The 5680s are bolted to the bottom of the case
Main power (+15V) comes from a universal 5A laptop power supply (with
selectable output voltage set to +15V). I used an old 10V brick to drive one
of the 7805 sent by the Chinese supplier with the 5680s. The rest is the odd
resistor and capacitor and wiring. Not pretty but very functional.

Front panel has: 2 switches (+15V to the Rbs): 2 red LEDS - power ON to the
RBs, 2 green LEDs - Lock, and two BNCs - 10 MHZ outout.

The only thing left is where to fit the teddy bear they sent...

Have fun with your projects!

Rob Kimberley


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of bob grant
Sent: 02 February 2012 23:20
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE5680 missing PPS soln

The LEDs are common garden variety, tied to +5V and inline with 1k8...I was
expecting 2ma or so. 
Note, whereas the PPS signal is buffered the LOCK signal for the DB9 is not
passed though the 74ACT240 buffer. 


On Thu, Feb 2, 2012, at 11:10 PM, Attila Kinali wrote:
> On Thu, 02 Feb 2012 12:46:01 -0800
> bob grant  wrote:
> 
> > Some info...
> > 
> > Its tempting to attach an LED to the /LOCK signal on the DB9.
> > However this signal is very weak and the LED does not seem very 
> > bright and PPS signal does not pulse...Hmm
> > 
> > Internally the /LOCK pin is connected the 74AC240 buffer, but with 
> > an LED helping to keep the signal voltage high (2.3V) a logic low is 
> > never asserted.
> 
> May i ask what kind of LED you connected and at which current you 
> drove it? I don't know which 74AC240 the FE5680 units use, but 
> Fairchild lists theirs with an absolute maximum rating of +/-50mA.
> I wouldn't use it to drive more than 20mA, which means that you need 
> at least a current generation LED, or better a high efficiency LED.
> Such as John Lofgren used. Alternatively, use a small logic level P 
> channel FET like the FDV302P or a small PNP.
> 
> 
>   Attila Kinali
> 
> [1] For those who don't know, Absolute Maximum Ratings should read as 
> "If you exceede these levels, your device will be dead for sure!"
> --
> Why does it take years to find the answers to the questions one should 
> have asked long ago?
> 
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Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T

[Roberto Barrios]

Long time ago I built a Jupiter-T companion board that included the loop 
filter, divider and phase detector for the James Miller GPSDO. It also 
includes a PIC that monitors the NMEA strings and displays different status 
data via LEDs, and outputs data via RS232.


http://www.rbarrios.com/projects/10KGPSDO/

I used an ISOTEMP OCXO and it worked well.I also tried to implement a lock 
detection mechanism, first based on timing the phase detector and sencondly 
monitoring the swings of the EFC. I was not very happy with any of those 
solutions and finally gave up. Details are in the code.


Text is in spanish but you really don't need to read it, it is very, very 
basic for you time-nuts. If anyone has a suggestion for a better lock 
detection solution applicable here, I'd love to know about it.


Best regards,
Roberto EB4EQA

-Mensaje original- 
From: Tom Van Baak

Sent: Thursday, February 02, 2012 11:56 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T


This thread got started when someone asked if an analog PLL would work
for building a GSPDO.  For that you do need timing pulses much faster
then 1PPS.

But the analog PLL are not the way to go for best accuracy.


Remarkably, the simplest and still one of the best GPSDO I've
tested was the 10 kHz Jupiter and analog PLL-based standard
by James Miller. It performed superbly. It's the 4th GPSDO at:
http://www.leapsecond.com/pages/gpsdo/

True, there exist some better GPSDO, and you need digital if
you want a hold-over feature, but I wouldn't discourage anyone
from trying the analog PLL method. The sheer simplicity might
more than make up for a few less ns. Miller's page is at:
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm

/tvb



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Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T

[Azelio Boriani]

I have implemented a digital lock detector in my CPLD timing the phase
detector itself. It was years ago... let me find the VHDL code so that can
give any idea how to implement it for a microprocessor.

On Fri, Feb 3, 2012 at 10:58 AM, Roberto Barrios  wrote:

> Long time ago I built a Jupiter-T companion board that included the loop
> filter, divider and phase detector for the James Miller GPSDO. It also
> includes a PIC that monitors the NMEA strings and displays different status
> data via LEDs, and outputs data via RS232.
>
> http://www.rbarrios.com/**projects/10KGPSDO/
>
> I used an ISOTEMP OCXO and it worked well.I also tried to implement a lock
> detection mechanism, first based on timing the phase detector and sencondly
> monitoring the swings of the EFC. I was not very happy with any of those
> solutions and finally gave up. Details are in the code.
>
> Text is in spanish but you really don't need to read it, it is very, very
> basic for you time-nuts. If anyone has a suggestion for a better lock
> detection solution applicable here, I'd love to know about it.
>
> Best regards,
> Roberto EB4EQA
>
> -Mensaje original- From: Tom Van Baak
> Sent: Thursday, February 02, 2012 11:56 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T
>
>  This thread got started when someone asked if an analog PLL would work
>> for building a GSPDO.  For that you do need timing pulses much faster
>> then 1PPS.
>>
>> But the analog PLL are not the way to go for best accuracy.
>>
>
> Remarkably, the simplest and still one of the best GPSDO I've
> tested was the 10 kHz Jupiter and analog PLL-based standard
> by James Miller. It performed superbly. It's the 4th GPSDO at:
> http://www.leapsecond.com/**pages/gpsdo/
>
> True, there exist some better GPSDO, and you need digital if
> you want a hold-over feature, but I wouldn't discourage anyone
> from trying the analog PLL method. The sheer simplicity might
> more than make up for a few less ns. Miller's page is at:
> http://www.jrmiller.demon.co.**uk/projects/ministd/frqstd.htm
> http://www.jrmiller.demon.co.**uk/projects/ministd/frqstd0.**htm
>
> /tvb
>
>
>
> __**_
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] HP5334B with 10544 OCXO

[Roy Phillips]

Randall
Thank you for your info. - I have now had time to check my manual and there 
is a section that deals with a "customer" installed OCXO. I intend doing the 
simple mod. today. Some months ago I obtained a 5328A  for my collection of 
HP counters, and I was very surprised at its quick and accurate oven (10544) 
operation.

Regards
Roy



-Original Message- 
From: Dave M

Sent: Tuesday, January 31, 2012 12:01 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] HP5334B with 10544 OCXO



There is a section in the HP5334 Service manual on changes needed.

The oscillator uses either the internal crystal (The trimmer is
connected to) or the 10811.

Basically you change a capacitor feeding from one to the other.

I could scan the appropriate pages if you need (Contact me off list).

Regards

Randall Prentice
Stokes Valley
Lower Hutt5019
New Zealand
ZL2RJP

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]
On Behalf Of Roy Phillips
Sent: Tuesday, 31 January 2012 10:40 a.m.
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP5334B with 10544 OCXO

Mark
By chance I have just today installed a recently acquired 10554 OCXO
into my HP 5334B Counter.  Its has been running for 5 hours and is
yet to stabilize - my Manual suggest that 24 hours is the required
time. Despite reading the manual, I cannot see any reference to the
change over from the "low grade" inbuilt oscillator - is this
automatic or does it require a jumper alteration.  I seem to recall
that Rick Karlquist  referred to a voltage "droop" in the PSU
occurring, due to the additional load of the oven as a consequence of
fitting the OCXO to the 5334B.  I assume that this is when the oven
is taking maximum current - perhaps he will offer some help (again)
as I cannot find his earlier comments ?  I note that the rear
"simple" oscillators trimmer is still operative - should this be so
?, or is it indicative to a need to disconnect it ?
Again, any comments would be appreciated.
Regards
Roy



Installation of Option 010 is basically removing capacitor C8 and
reinstalling it into the holes designated for C100.  Install the 10544
oscillator into the receptacle, secure with appropriate screws and you're
all set.  C8 and C100 are located very close to the standard (low-stability)
crystal at the rear of the main board.

Dave M
A woman has the last word in any argument. Anything a man says after that is
the beginning of a new argument.



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Re: [time-nuts] HP5334B with 10544 OCXO

[Roy Phillips]

Rick
Thanks again for your comments on the 10544 OCXO installation in a 5334B 
counter. My initial result was because of my haste to check the working of 
the OCXO, and obviously both oscillators were operative. The Service Manual 
gives clear instructions for a customer "retro" installation which I hope to 
carry out over the week-end. I thought that you had also made some comment 
that the power supply was somewhat "stretched" by this addition, (voltage 
droop), but that was sometime ago, and perhaps it did not apply to the 
5334B.  It would seem to be OK,and the power transformer runs very cool.

Regards
Roy

"-Original Message- 
From: Rick Karlquist

Sent: Monday, January 30, 2012 10:43 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP5334B with 10544 OCXO

Roy Phillips wrote:

Mark
By chance I have just today installed a recently acquired 10554 OCXO into
my
HP 5334B Counter.  Its has been running for 5 hours and is yet to
stabilize - my Manual suggest that 24 hours is the required time. Despite
reading the manual, I cannot see any reference to the change over from the
"low grade" inbuilt oscillator - is this automatic or does it require a
jumper alteration.  I seem to recall that Rick Karlquist  referred to a
voltage "droop" in the PSU occurring, due to the additional load of the
oven
as a consequence of fitting the OCXO to the 5334B.  I assume that this is
when the oven is taking maximum current - perhaps he will offer some help
(again) as I cannot find his earlier comments ?  I note that the rear
"simple" oscillators trimmer is still operative - should this be so ?, or
is
it indicative to a need to disconnect it ?
Again, any comments would be appreciated.
Regards
Roy


I inherited the built in oscillator from the 5334A; it is a poor
design based on a 10116 ECL line receiver (HP part no 1820-0810,
near the rear panel switch that selects the external reference).
I believe that spare gates in the package are used to select the
10811 vs built in vs external ref.  I don't remember, but I suspect
plugging in the 10811 is detected somehow by the 10116.  I wouldn't
normally allow a design where it wasn't automatic.

When you say the rear panel trimmer is still operative, do you mean
it affects the frequency?  Is so, you are not running on the 10544.
The design should be obvious from the schematic, however I don't
have one and can't remember every detail from 25 years ago.

Rick


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Re: [time-nuts] FE5680 missing PPS soln

[Attila Kinali]

On Fri, 3 Feb 2012 09:50:52 -
"Rob Kimberley"  wrote:

> Mine was a green LED out of the junk box, but I did use 330R in series. 1k8
> seems rather large.

Then i'm not surprised that your FE-5680 refused to work :-)

Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute
maximum rating at 50mA. For a general logic output, i wouldn't recomend
to draw more than 10mA (as Bob Grant wrote, the lock signal doesn't
seem to pass trough the 74AC240). Hence, i would say that 330R seems
rather small :-)

Keep in mind that you drove circuit at over current for quite a long
time. The circuit is most likely damaged (if they dont have an over
current limit, which i doubt). If for an unknown reason the lock signal
fails in the future, it might be due to this.

Attila Kinali
-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] FE5680 missing PPS soln

[Reeves Paul]

9mA

PaulG8GJA 

-Original Message-
From: Attila Kinali [mailto:att...@kinali.ch] 
Sent: 03 February 2012 12:55
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE5680 missing PPS soln

On Fri, 3 Feb 2012 09:50:52 -
"Rob Kimberley"  wrote:

> Mine was a green LED out of the junk box, but I did use 330R in 
> series. 1k8 seems rather large.

Then i'm not surprised that your FE-5680 refused to work :-)

Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute maximum
rating at 50mA. For a general logic output, i wouldn't recomend to draw more
than 10mA (as Bob Grant wrote, the lock signal doesn't seem to pass trough
the 74AC240). Hence, i would say that 330R seems rather small :-)

Keep in mind that you drove circuit at over current for quite a long time.
The circuit is most likely damaged (if they dont have an over current limit,
which i doubt). If for an unknown reason the lock signal fails in the
future, it might be due to this.

Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved up
a whole truckload of damned heavy brick arguments and then you dump them all
out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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[time-nuts] FE5680 missing PPS soln

[Mark Sims]

Uhhh... last time I checked 3V/330 ohms is 9.1 milliamps,  not 90 mA...

-
Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA
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Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs andinterconnect

[J. L. Trantham]

Randy,

I checked Didier's site and there is some information there but I seem to
remember a more detailed description with pictures of the cables, etc.  I
can't remember if it applied to the RFTGm or the RFTGm-II.

Perhaps they are the same.

I still haven't found what I seem to remember though.

Thanks,

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Randy D. Hunt
Sent: Thursday, February 02, 2012 11:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs
andinterconnect


check Dedier's site ___


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Re: [time-nuts] FE5680 missing PPS soln

[Rob Kimberley]

Thank you Paul.
:-)

Rob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Reeves Paul
Sent: 03 February 2012 12:59
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] FE5680 missing PPS soln

9mA

PaulG8GJA 

-Original Message-
From: Attila Kinali [mailto:att...@kinali.ch]
Sent: 03 February 2012 12:55
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE5680 missing PPS soln

On Fri, 3 Feb 2012 09:50:52 -
"Rob Kimberley"  wrote:

> Mine was a green LED out of the junk box, but I did use 330R in 
> series. 1k8 seems rather large.

Then i'm not surprised that your FE-5680 refused to work :-)

Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute maximum
rating at 50mA. For a general logic output, i wouldn't recomend to draw more
than 10mA (as Bob Grant wrote, the lock signal doesn't seem to pass trough
the 74AC240). Hence, i would say that 330R seems rather small :-)

Keep in mind that you drove circuit at over current for quite a long time.
The circuit is most likely damaged (if they dont have an over current limit,
which i doubt). If for an unknown reason the lock signal fails in the
future, it might be due to this.

Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved up
a whole truckload of damned heavy brick arguments and then you dump them all
out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] FE5680 missing PPS soln

[Attila Kinali]

On Fri, 3 Feb 2012 13:02:11 +
Mark Sims  wrote:

> > Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
> > 3V/330R = 90mA
>
> Uhhh... last time I checked 3V/330 ohms is 9.1 milliamps,  not 90 mA...

Uhh... last time i checked... i should have used a calculator ^^;

Sorry, please disregard what i wrote.

Attila Kinali
-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] FE5680 missing PPS soln

[Rob Kimberley]

Hi,

You need to check your maths...

:-)
Rob K

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Attila Kinali
Sent: 03 February 2012 12:55
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE5680 missing PPS soln

On Fri, 3 Feb 2012 09:50:52 -
"Rob Kimberley"  wrote:

> Mine was a green LED out of the junk box, but I did use 330R in 
> series. 1k8 seems rather large.

Then i'm not surprised that your FE-5680 refused to work :-)

Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute maximum
rating at 50mA. For a general logic output, i wouldn't recomend to draw more
than 10mA (as Bob Grant wrote, the lock signal doesn't seem to pass trough
the 74AC240). Hence, i would say that 330R seems rather small :-)

Keep in mind that you drove circuit at over current for quite a long time.
The circuit is most likely damaged (if they dont have an over current limit,
which i doubt). If for an unknown reason the lock signal fails in the
future, it might be due to this.

Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved up
a whole truckload of damned heavy brick arguments and then you dump them all
out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] HP5334B with 10544 OCXO

[Roy Phillips]

Thanks to Dave and Randall - - yes I did discover the "change-over" 
instructions, and hope to make the change over the week-end.

Roy


-Original Message- 
From: Dave M

Sent: Tuesday, January 31, 2012 12:01 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] HP5334B with 10544 OCXO



There is a section in the HP5334 Service manual on changes needed.

The oscillator uses either the internal crystal (The trimmer is
connected to) or the 10811.

Basically you change a capacitor feeding from one to the other.

I could scan the appropriate pages if you need (Contact me off list).

Regards

Randall Prentice
Stokes Valley
Lower Hutt5019
New Zealand
ZL2RJP

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]
On Behalf Of Roy Phillips
Sent: Tuesday, 31 January 2012 10:40 a.m.
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP5334B with 10544 OCXO

Mark
By chance I have just today installed a recently acquired 10554 OCXO
into my HP 5334B Counter.  Its has been running for 5 hours and is
yet to stabilize - my Manual suggest that 24 hours is the required
time. Despite reading the manual, I cannot see any reference to the
change over from the "low grade" inbuilt oscillator - is this
automatic or does it require a jumper alteration.  I seem to recall
that Rick Karlquist  referred to a voltage "droop" in the PSU
occurring, due to the additional load of the oven as a consequence of
fitting the OCXO to the 5334B.  I assume that this is when the oven
is taking maximum current - perhaps he will offer some help (again)
as I cannot find his earlier comments ?  I note that the rear
"simple" oscillators trimmer is still operative - should this be so
?, or is it indicative to a need to disconnect it ?
Again, any comments would be appreciated.
Regards
Roy



Installation of Option 010 is basically removing capacitor C8 and
reinstalling it into the holes designated for C100.  Install the 10544
oscillator into the receptacle, secure with appropriate screws and you're
all set.  C8 and C100 are located very close to the standard (low-stability)
crystal at the rear of the main board.

Dave M
A woman has the last word in any argument. Anything a man says after that is
the beginning of a new argument.



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Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs andinterconnect

[Randy D. Hunt]

On 2/3/2012 5:32 AM, J. L. Trantham wrote:

Randy,

I checked Didier's site and there is some information there but I seem to
remember a more detailed description with pictures of the cables, etc.  I
can't remember if it applied to the RFTGm or the RFTGm-II.

Perhaps they are the same.

I still haven't found what I seem to remember though.

Thanks,

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Randy D. Hunt
Sent: Thursday, February 02, 2012 11:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs
andinterconnect


check Dedier's site ___


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There is a lot of info in the archives on this list.  The most detailed 
connection i recall was for the 'RFG' series units Do a search for RFTG 
and be prepared to read a lot of hits.  I have a 'RFTG' pair wired per 
info from this site and are very happy with the results. unfortunately I 
just moved (last weekend) and don't have access to my equipment.

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Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outsandinterconnect

[Stanley]

try : http://www.n4iqt.com/lucentgps/
and : http://www.n4iqt.com/rfgmxo/

not sure if it is any help been a while I spent any time working on them,

Stanley




- Original Message - 
From: "Randy D. Hunt" 
To: "Discussion of precise time and frequency measurement" 


Sent: Friday, February 03, 2012 8:48 AM
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin 
outsandinterconnect



On 2/3/2012 5:32 AM, J. L. Trantham wrote:

Randy,

I checked Didier's site and there is some information there but I seem to
remember a more detailed description with pictures of the cables, etc.  I
can't remember if it applied to the RFTGm or the RFTGm-II.

Perhaps they are the same.

I still haven't found what I seem to remember though.

Thanks,

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Randy D. Hunt
Sent: Thursday, February 02, 2012 11:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs
andinterconnect


check Dedier's site ___


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and follow the instructions there.

There is a lot of info in the archives on this list.  The most detailed 
connection i recall was for the 'RFG' series units Do a search for RFTG 
and be prepared to read a lot of hits.  I have a 'RFTG' pair wired per 
info from this site and are very happy with the results. unfortunately I 
just moved (last weekend) and don't have access to my equipment.

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and follow the instructions there.




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Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pinoutsandinterconnect

[Stanley]

This is one I was thinking about some German : 
http://www.n4iqt.com/lucentgps/small_notes_rftg-m-xo.jpg .


Still looking know that I have some more info somewhere ...

Stanley

- Original Message - 
From: "Stanley" 
To: "Discussion of precise time and frequency measurement" 


Sent: Friday, February 03, 2012 11:09 AM
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb 
pinoutsandinterconnect




try : http://www.n4iqt.com/lucentgps/
and : http://www.n4iqt.com/rfgmxo/

not sure if it is any help been a while I spent any time working on them,

Stanley




- Original Message - 
From: "Randy D. Hunt" 
To: "Discussion of precise time and frequency measurement" 


Sent: Friday, February 03, 2012 8:48 AM
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin 
outsandinterconnect



On 2/3/2012 5:32 AM, J. L. Trantham wrote:

Randy,

I checked Didier's site and there is some information there but I seem 
to
remember a more detailed description with pictures of the cables, etc. 
I

can't remember if it applied to the RFTGm or the RFTGm-II.

Perhaps they are the same.

I still haven't found what I seem to remember though.

Thanks,

Joe

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Randy D. Hunt
Sent: Thursday, February 02, 2012 11:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs
andinterconnect


check Dedier's site ___


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and follow the instructions there.

There is a lot of info in the archives on this list.  The most detailed 
connection i recall was for the 'RFG' series units Do a search for RFTG 
and be prepared to read a lot of hits.  I have a 'RFTG' pair wired per 
info from this site and are very happy with the results. unfortunately I 
just moved (last weekend) and don't have access to my equipment.

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and follow the instructions there.




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Re: [time-nuts] FE5680 missing PPS soln

[Don Latham]

I'm using a 556 dual timer, one section as an inverter to drive a lock
led, and the other section as a pulse stretcher to drive a 1 pps led.
Let's get on with it.
Don

Attila Kinali
> On Fri, 3 Feb 2012 09:50:52 -
> "Rob Kimberley"  wrote:
>
>> Mine was a green LED out of the junk box, but I did use 330R in
>> series. 1k8
>> seems rather large.
>
> Then i'm not surprised that your FE-5680 refused to work :-)
>
> Just calculate: 5V supply, approx 2V LED voltage -> 3V over the
> resistor.
> 3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute
> maximum rating at 50mA. For a general logic output, i wouldn't recomend
> to draw more than 10mA (as Bob Grant wrote, the lock signal doesn't
> seem to pass trough the 74AC240). Hence, i would say that 330R seems
> rather small :-)
>
> Keep in mind that you drove circuit at over current for quite a long
> time. The circuit is most likely damaged (if they dont have an over
> current limit, which i doubt). If for an unknown reason the lock signal
> fails in the future, it might be due to this.
>
>   Attila Kinali
> --
> The trouble with you, Shev, is you don't say anything until you've saved
> up a whole truckload of damned heavy brick arguments and then you dump
> them all out and never look at the bleeding body mangled beneath the
> heap
>   -- Tirin, The Dispossessed, U. Le Guin
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>


-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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[time-nuts] (OT) linkedin spam

[lists]

Just a FYI, you can request Linkedin to get on a "do not contact" list. This 
way every time someone gets their address book harvested, you won't get 
spammed. Below is the relevant part of an email I got from Linkedin.
-- 

Per your request, the email provided has been added to our "do not contact" 
list. You will no longer receive any email from LinkedIn or our members on this 
email address. If you decide at a later date that you want to set up a LinkedIn 
account, you will need to first contact us to have your email address removed 
from the “do not contact” list.
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Re: [time-nuts] (OT) linkedin spam

[J. Forster]

In theory only. I have been on both FaceBook and LinkedIn "Do Not Contact"
lists, and I got another spam within the last two days.


-John

==


> Just a FYI, you can request Linkedin to get on a "do not contact" list.
> This way every time someone gets their address book harvested, you won't
> get spammed. Below is the relevant part of an email I got from Linkedin.
> --
>
> Per your request, the email provided has been added to our "do not
> contact" list. You will no longer receive any email from LinkedIn or our
> members on this email address. If you decide at a later date that you want
> to set up a LinkedIn account, you will need to first contact us to have
> your email address removed from the “do not contact” list.
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>
>



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[time-nuts] FE-5680A Manual - dated November 2002

[Bob Smither]

Thanks Rob Kimberley!

The manual that Rob found (Technical Manual TM 5680-0211) is available here:

  http://c-c-i.com/node/166

Best regards,
-- 
Bob Smither, PhD   Circuit Concepts, Inc.
=
Blessed is he who expects no gratitude, for he shall not be disappointed.
  -- W. C. Bennett
=
smit...@c-c-i.com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)
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Re: [time-nuts] 32768 Hz from 10 MHz

[Orin Eman]

On Fri, Feb 3, 2012 at 1:08 AM, Dennis Ferguson  wrote:

>
> On 3 Feb, 2012, at 14:15 , Orin Eman wrote:
>
> > On Thu, Feb 2, 2012 at 7:16 PM, Hal Murray 
> wrote:
> >
> >>
> >>> It's possible to use Bresenham with two integers 10,000,000 and 32,768
> >> but I
> >>> found no way to perform all the 24-bit calculations on an 8-bit PIC
> quick
> >>> enough. Removing the GCD often helps but in this case the accumulator
> >>> remains 3-bytes wide.
> >>
> >>> To generate 32 kHz you have to toggle a pin and calculate if the next
> >> toggle
> >>> must be 38 or 39 instructions in the future; all the math must occur
> >> within
> >>> 37 instructions. That's why I came up with the binary leap year kind of
> >>> algorithm; it's as close to math-less as you can get.
> >>
> >> You missed the simple way.  Table lookup.  :)
> >>
> >> The table is only 256 slots long.
> >>
> >> That's toggling between 305 and 306 cycles.  If your CPU uses N clocks
> per
> >> instruction, multiply the table size by N.
> >>
> >
> >
> >
> > Well, I thought table lookup too, but I figured  a 2048 x 1 table.
>  Easily
> > done with a rotating bit and 256 byte table.
> >
> >
> > Assuming clocking a PIC at 10MHz, you have 2,500,000 instructions per
> > second.  Since there was talk about time to the next toggle, we have
> > 2,500,000/65536 instructions between toggles, ie 38.1470... instructions.
> > The fraction turns out to be 301/2048, so you have to distribute 301
> extra
> > instructions over every 2048 half-periods of the 32768Hz waveform.
>
> I only barely know the instruction set on those processors, but it seems
> like it should be way easier than that.  You know it is going to be 38 or
> 39 instructions, so that only question is when it should be 39.  The value
> of 250/65536 is 38.1470… in decimal, but in hex it is exactly 26.25a;
> that is the 0x26 is 38 decimal while the fractional part is only 10 bits
> long.  This means you should be able to compute when the extra cycle is
> required by keeping a 16 bit accumulator to which the fractional part
> 0x25a0 is added at every change and executing the extra instruction when
> there is a carry out of that. The seems straight forward.  If `lo' and `hi'
> are the two halves of the accumulator then the working part of this becomes
> something like (excusing my PIC assembler, which I mostly forget):
>
>movl0xa0,w  // low byte of increment into w
>add w,lo// add w to lo, may set carry
>movl0x25,w  // high byte of increment into w
>btfsc   3,0 // skip next if carry clear
>add one,w   // increment w by one; I'm not sure how to do that
>add w,hi// add w to hi, may set carry
>// if carry set here need extra instruction.  Maybe this does it?
>btfss   3,0 // skip if carry set
>gotoblorp   // carry clear, don't execute next instruction
>nop // the extra instruction
> blorp:
>// enough instructions more to make 38/39
>
> Maybe someone who knows what they're doing can interpret that?
>


Here you go:

 movlw 0xa0
 addwf  lo,f
 movlw 0x25
 btfsc  status,C
 addlw 1; or movlw 0x26
 addwf hi,f
 btfss  status,C
 goto   skip
 nop
 nop
skip:


Takes 9 or 10 instruction cycles.  You needed an extra nop as the goto
takes two cycles, one cycle if skipped.  I'd just reverse the sense as
follows:

btfsc  status,C
goto   skip
skip:

If carry is clear, skipping the goto takes one instruction cycle.  If carry
is set, executing the goto takes two instruction cycles.  Yes, the goto is
to the next inline instruction, but as far as I know, the PIC doesn't
optimise that.  The entire sequence in this case would take 8 or 9
instruction cycles.

I'd forgotten the trick of using binary fixed point arithmetic with the
fractional part strategically placed at a byte boundary!  I've used a
similar trick in the past to convert a binary fraction into decimal digits
- keep multiplying by 10 (a couple of shifts plus an add), pick up the
non-fractional bits as the next decimal digit, then truncate to the
remaining fractional bits.

Orin.
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Re: [time-nuts] FE-.5680A trimming resolution

[shalimr9]

Rob,

Can you upload it to my site?

www.ko4bb.com/manuals/

THANKS IN ADVANCE,

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-Original Message-
From: "Rob Kimberley" 
Sender: time-nuts-boun...@febo.com
Date: Tue, 31 Jan 2012 21:14:59 
To: 'Discussion of precise time and frequency measurement'
Reply-To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] FE-.5680A trimming resolution

If anyone is interested, I have just got hold of a PDF of the Technical Manual 
TM 5680-0211 for 5680A series Rubidiums. 
Please contact me off list for a copy (1M, so too large to post on 
time-nuts@febo.com)

Rob Kimberley

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Attila Kinali
Sent: 31 January 2012 20:47
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE-.5680A trimming resolution

On Tue, 31 Jan 2012 21:06:04 +0100
Javier Herrero  wrote:

> El 31/01/2012 20:43, Attila Kinali escribi :
> > My current progress is that the uC i wanted to use does not do what 
> > i want. Can anyone recommend a uC with 32bit timers and IEEE 1588 support?
> You can have a look on these
> http://www.ti.com/mcu/docs/mculuminaryfamilynode.tsp?sectionId=95&tabI
> d=2597&familyId=1756 Some of them have IEEE-1588, like the LM3S9B96

This was exactly the device i intended to use.
But it doesnt really have 32bit timers. They cascade two 16bit timers to get 
32bit, but then all kind of restrictions apply which make the timers unusable. 
And when using 16bit timers, i'll get an overflow every 800us (at 80MHz clock).

I browsed trough the internets and could find the following devices:

LPC18xx (NXP): 
Look nice, but still in development or early production.
I especially like that they (will be) are available in a 200 pin QFP.
This would enable to use all the functions of the chip while still being able 
to solder one by hand.

K60 (Freescale): Hell of a confusing documentation. Also quite new.
Have only 16bit timers. A big issue is that they have a crypto unit on chip, 
which makes them export restricted. Ie the only way to buy them is from a local 
distributor which makes them expensive.

STM32-F2/F4 (ST): ST doesn't want to give me the documentation to those.
(website fails w/o error message)


I havent found any other chips yet. Sofar the options i see are:
* wait for the LPC18xx become available in quanities (can take a year)
* Use a LM3S9B96 together with a small FPGA to implement the counter functions.

Any hints appreciated

Attila Kinali

--
Why does it take years to find the answers to the questions one should have 
asked long ago?

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[time-nuts] 5680 performance very first impressions.

[Mark Spencer]

I've seen some comments and questions regarding the performance of the 5680 
Rb's.

 Yesterday I took delivery of two 5680's.   In case anyone is interested, I'm 
seeing adev numbers in the 2 to 2.5 E-12 range from 80 thru 200 seconds.   The 
unit under test has been running for approx one hour and I let it warm up for 
30 minutes before collecting data.

The reference is an fts1050 and the data is being collected with an hp 5370B.

Not to bad for $40.00 IMHO.

Regards Mark Spencer
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[time-nuts] Rubidium Performance

[John Ackermann N8UR]

Someone earlier today made the point that for all the talk about the FEI rubes, 
there hasn't been any real performance info posted.  That prodded me to start 
an experiment I've been meaning to do for a while.  I have samples of all three 
of the common telco Rb standards -- Efratom FRS, Datum LPRO, and Fe8-5680.

Over the next couple of days I'll do measurement runs of each of the three 
versus an HP-5065A laboratory Rb (for ADEV), and a Wenzel ULN (for phase 
noise).  I'll collect long enough to get solid ADEV out to at least 1000 second 
tau on each unit.  I have the FRS test running now.

If all goes well, I'll post the results early next week.

John
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Re: [time-nuts] Rubidium Performance

[Brian, WA1ZMS]

Thanks John!


-Brian, WA1ZMS


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of John Ackermann N8UR
Sent: Friday, February 03, 2012 9:41 PM
To: Time-Nuts
Subject: [time-nuts] Rubidium Performance

Someone earlier today made the point that for all the talk about the FEI
rubes, there hasn't been any real performance info posted.  That prodded me
to start an experiment I've been meaning to do for a while.  I have samples
of all three of the common telco Rb standards -- Efratom FRS, Datum LPRO,
and Fe8-5680.

Over the next couple of days I'll do measurement runs of each of the three
versus an HP-5065A laboratory Rb (for ADEV), and a Wenzel ULN (for phase
noise).  I'll collect long enough to get solid ADEV out to at least 1000
second tau on each unit.  I have the FRS test running now.

If all goes well, I'll post the results early next week.

John
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Re: [time-nuts] Rubidium Performance

[John Miles]

> Someone earlier today made the point that for all the talk about the FEI
> rubes, there hasn't been any real performance info posted.  That prodded
> me to start an experiment I've been meaning to do for a while.  I have
> samples of all three of the common telco Rb standards -- Efratom FRS,
> Datum LPRO, and Fe8-5680.
> 
> Over the next couple of days I'll do measurement runs of each of the three
> versus an HP-5065A laboratory Rb (for ADEV), and a Wenzel ULN (for phase
> noise).  I'll collect long enough to get solid ADEV out to at least 1000
second
> tau on each unit.  I have the FRS test running now.
> 
> If all goes well, I'll post the results early next week.

I'm doing some short-term runs on the ones I have around here, as well
(FE-5680A, PRS-10, LPRO).  Will be interesting to see how close ours are. 

So far, the FE-5680A is doing well in the ADEV department, but its AD9832
DDS chip adds some substantial noise and spurs to the 10 MHz output.  Does
yours have that chip?  I understand that some of them didn't.

The overall SSB C/N ratio I'm seeing between 1 Hz - 100 kHz is pretty much
in line with Analog Devices' data sheet, as are the spur levels.  

-- john



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Re: [time-nuts] Rubidium Performance

[Mark Spencer]

Once my first unit has warmed up properly I'll be curious to see how the adev 
compares (I can't measure phase noise.)  If any one is interested I've also got 
some adev data from my one working temex lpfrs Rb unit.   (I also have another 
unit that only locks once in a while.)At approx 1/3 the price the 5680 
seems like a better bargain especially if the 1pps output works.

Thanks in advance to those who can properly evaluate these units.   

Regards Mark S



On 2012-02-03, at 7:19 PM, "John Miles"  wrote:

>> Someone earlier today made the point that for all the talk about the FEI
>> rubes, there hasn't been any real performance info posted.  That prodded
>> me to start an experiment I've been meaning to do for a while.  I have
>> samples of all three of the common telco Rb standards -- Efratom FRS,
>> Datum LPRO, and Fe8-5680.
>> 
>> Over the next couple of days I'll do measurement runs of each of the three
>> versus an HP-5065A laboratory Rb (for ADEV), and a Wenzel ULN (for phase
>> noise).  I'll collect long enough to get solid ADEV out to at least 1000
> second
>> tau on each unit.  I have the FRS test running now.
>> 
>> If all goes well, I'll post the results early next week.
> 
> I'm doing some short-term runs on the ones I have around here, as well
> (FE-5680A, PRS-10, LPRO).  Will be interesting to see how close ours are. 
> 
> So far, the FE-5680A is doing well in the ADEV department, but its AD9832
> DDS chip adds some substantial noise and spurs to the 10 MHz output.  Does
> yours have that chip?  I understand that some of them didn't.
> 
> The overall SSB C/N ratio I'm seeing between 1 Hz - 100 kHz is pretty much
> in line with Analog Devices' data sheet, as are the spur levels.  
> 
> -- john
> 
> 
> 
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Re: [time-nuts] FE-5680A 1 pps photo

[Bob Bownes]

Just for completeness sake, here is a screen capture off of my DSA-602 of
the 1pps. Note that the trace starts 500ns _before_ the 1pps triggers the
capture. Ah the wonders of digital sampling.


http://www.fastbobs.com/pictures/1pps.jpg

Also as a pdf

http://www.fastbobs.com/pictures/1pps.pdf

Bob


On Thu, Feb 2, 2012 at 1:20 PM, John Howell  wrote:

> Not odd but my mistake, I took a picture on both 'scopes and the Fluke
> gave marginally better results, the text referred to the wrong one. Sorry
> for the confusion.
>
> On 2 Feb 2012, at 16:43, David wrote:
>
> > Odd.  Did Tektronix mark it Fluke PM3082? :)
> >
> > It is nice to know that the current generation of digital cameras can
> > be used for this application.  It is too bad that the image has so
> > much noise.
> >
> > On Thu, 2 Feb 2012 16:27:03 +, John Howell 
> > wrote:
> >
> >> and here's another photo of the pulse from one of the newer
> breed of FE-5680A that require the 5V.
> >> Taken with a Sony Cybershot H5, 8 sec exposure, 'scope is an elderly
> Tektronix 2252
> >>
> >> http://dl.dropbox.com/u/1690159/1PPS_1%20FE-5680E.jpg
> >>
> >> On 2 Feb 2012, at 15:50, Alberto di Bene wrote:
> >>
> >>> I managed to take a photo at the scope screen showing the 1 pps pulse
> >>> from an old FE-5680A (the one that does not need the 5V and does not
> >>> output the oscillator signal - just the 1pps).
> >>>
> >>> Exposure was 30 sec, F9. The signal was barely visible with naked eye,
> >>> and some jittering is present. The room of course was in complete
> >>> darkness, but the reflex of the stand-by led of another instrument
> >>> can be seen...
> >>>
> >>> http://dl.dropbox.com/u/15089947/1pps.gif
>
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Re: [time-nuts] Rubidium Performance: DDS noise effect on 10 MHz

[beale]

>  From: John Miles 
>  So far, the FE-5680A is doing well in the ADEV department, but its AD9832
>  DDS chip adds some substantial noise and spurs to the 10 MHz output. [...]
>  The overall SSB C/N ratio I'm seeing between 1 Hz - 100 kHz is pretty much
>  in line with Analog Devices' data sheet, as are the spur levels.  

In the current 5680A units, the 10 MHz output comes from the 60 MHz VCXO 
(divided by 6 in CPLD) and not direct from a DDS. If my architecture 
understanding is right, the DDS signal output is mixed with the VCXO output 
only at the 114th harmonic of 60 MHz, and it's the PLL (looking at the optical 
signal from the Rb) that drives the VCXO to keep it lined up.  As I understand 
it, DDS phase noise should be divided by a factor of 6*114 by the time it 
appears at the 10 MHz output, and at larger frequency offsets the amplitude 
should also be (significantly) reduced by the PLL loop filter.

I don't have any phase noise measurement tools myself, so this is just an 
academic argument, but if there is significantly more noise on the 10 MHz than 
expected for a 60 MHz VCXO, I wonder if it's just inadequate filtering of an 
internal power rail.  Is the unit under test being driven by a linear, or 
switching supply?

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Re: [time-nuts] 32768 Hz from 10 MHz

[Hal Murray]

t...@leapsecond.com said:
> I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the
> lowest possible jitter?

What do you mean by high-end DDS?  A chip from Analog Devices or one from 
Xilinx? :)

If you use a classic DDS chip with a binary adder and ROM, it will have low 
jitter but the frequency will be off a tiny bit.  My calculations...

24 bits:
  54975 => 32767.653465
  54976 => 32768.249511

32 bits:
  14073748 => 32767.998054
  14073749 => 32768.000382


If you use a FPGA, it's something like this:
  X = X + 32768
  If X >= 1000
output clock pulse
X = X - 1000

You get the subtract for free if you are using decimal arithmetic and ignore 
the overflow.  You can do it with binary addition if you pipeline things 
right and put a mux in front of the adder.  It either adds 32K or adds 
(32K-10M).

That makes a 1 clock wide clock pulse, 100 ns at 10 MHz.  If you want a 
square clock, make a 2X clock and toggle a FF to divide by 2.

It will have the right long term frequency, or at least as good as the input 
clock.

It will have lots of jitter.  It's not Gaussian type jitter but spurs.  
Peak-to-peak will be roughly one clock period.

--

I don't know how to compute the jitter on traditional (binary, ROM) DDS 
chips.  Peak to peak will also be roughly one clock period in the raw output, 
but the output is close to a sine wave so some filtering would easily reduce 
the jitter.

I'm pretty sure they have spurs and that they are smaller and farther out if 
the ROM is wider and deeper.

Both DDS chips and FPGAs usually contain a PLL/DLL to get a faster internal 
clock rate.  That would reduce jitter.

I don't know enough matlab to be able to simulate this.  Another time sink when 
I get the time.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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