Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-21 Thread Magnus Danielson

On 04/20/2012 03:49 PM, ewkeh...@aol.com wrote:

It is a circuit that they for instance use in the 2110 where they take the
reference input in case of 10 MHz divide by 2 and also divide the 5 MHz
down to  500 Hz use an exor and out comes 5.000500 MHz filtered and divided by
5.


A similar approach is being used in many rubidiums to generate the 
5,3125 MHz signal, taking the 5 MHz, divide it by 16 and then XOR them 
together and then toss it through a LC tank to pick out the right 
frequency component. The rubidium is then tweaked using the C-field such 
that the locked 5 MHz lines up with SI second. That's just one aspect of 
why rubidiums have been relatively cheap from the start. The isotopic 
match of D lines allowing fairly easy filtering and selective pumping is 
another.



The  result is 1.000100 MHz which is mixed with the unknown divided to 1
MHz. The  result is 100 Hz counted with a 100 MHz period counter and you
have 1 E 12 in a  second. My counter which is part of the system and thanks to
Richard MCC is a  PIC, has 0.1, 1, 10 and 100 seconds gate time. The 100 or
200 MHz are generated  from the reference channel. All logic is in a
MAX3000A G/A. The output is RS 232  and can also be stored on a USB memory 
stick,
no PC needed. Austron uses a Xtal  as a filter and I use 2 because I do not
have access to their Xtal but it works.  A nicer solution would be to use an
AD 9833 DDS but it would require an   additional PIC to do the math since
the DDS can not produce an exact 1.000100  MHz. If some one is willing to do
that chip please contact me off list.


If you do quadrature signal multiplication, you can avoid the mirror 
frequency without high-Q filters. Look up the Tayloe detector for some 
inspiration.


In this case you can generate an I and Q signal by adding a DFF. By 
producing a 2 kHz and 500 Hz, you let the 500 Hz be the I signal and 
then let the additional DFF have that as D input and clocked by the 2 
KHz it will produce the 90 degree shifted Q signal on the Q output.


By quadrature separation of the 5 MHz you can then use the 5 MHz I and 
Q, mix and then analogue sum prior some mild filtering such as a LC-tank.


Cheers,
Magnus

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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread Attila Kinali
Moin

On Thu, 19 Apr 2012 18:18:24 -0400 (EDT)
ewkeh...@aol.com wrote:

 I have quite a collection of equipment and have build Dual Mixer, PICTIC  
 and what I think is best for you a circuit I call the Austron circuit.

What is this Austron Circuit? And how does it look like? :-)

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] Question about precise frequency / phase measurement

2012-04-20 Thread Attila Kinali
On Thu, 19 Apr 2012 23:39:32 +0200
skywatcher skywatc...@web.de wrote:


 BTW i'm using the 
 Parallax 'Propeller' controller
 which has 8 cores running at 80 MHz each, and can measure time intervals 
 with 12.5 ns resolution.
[...]

Looks like an interesting thing. But also very specialized.
If you have already experience with it, ok. But if you start
from scratch i would recomend to use one of the Cortex-M3
or Cortex-M4 processors. There is a lot more knowledge available
for these and you get a lot of tools just for free.



 I think the DDMTD could be a good solution.  The question is, if 74HCxx 
 parts would be good enough
 to get  1 mHz resolution for a 10 MHz frequency with an update rate of 
  1 sec.

That's a simple calculation. 1mHz of 10MHz is a precision of 10^-10.
Sampling at a second you need a time resolution of 1s*10^-10 = 0.1ns.
Modern CMOS (ie not HC/HCT) have a jitter in the region of 1-5ns. 
(ECL are in the region of a couple 100ps)

Ie, if you build a DDMTD with just HC/HCT, your jitter will be dominated
by the logic circuit and you have to average several samples to get
below the 10^-10 you want. ECL would be definilty better.

Also keep in mind, that in this region of precision, you have to model
your digial circuit partially as analog. Especially taking into account
that you have a a finite rise time, input and output jitter, power supply
noise, signal noise etc pp. All these will limit the precision you will
achieve for single measurements.

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] Question about precise frequency / phase measurement

2012-04-20 Thread Bruce Griffiths

Attila Kinali wrote:

On Thu, 19 Apr 2012 23:39:32 +0200
skywatcherskywatc...@web.de  wrote:


   

BTW i'm using the
Parallax 'Propeller' controller
which has 8 cores running at 80 MHz each, and can measure time intervals
with 12.5 ns resolution.
 

[...]

Looks like an interesting thing. But also very specialized.
If you have already experience with it, ok. But if you start
from scratch i would recomend to use one of the Cortex-M3
or Cortex-M4 processors. There is a lot more knowledge available
for these and you get a lot of tools just for free.



   

I think the DDMTD could be a good solution.  The question is, if 74HCxx
parts would be good enough
to get  1 mHz resolution for a 10 MHz frequency with an update rate of
  1 sec.
 

That's a simple calculation. 1mHz of 10MHz is a precision of 10^-10.
Sampling at a second you need a time resolution of 1s*10^-10 = 0.1ns.
Modern CMOS (ie not HC/HCT) have a jitter in the region of 1-5ns.
(ECL are in the region of a couple 100ps)
   
Not in this application, where DDJ and other pattern dependent jitter is 
absent.

4ps per inverter of flipflop is more typical for HCMOS.

Ie, if you build a DDMTD with just HC/HCT, your jitter will be dominated
by the logic circuit and you have to average several samples to get
below the 10^-10 you want. ECL would be definilty better.

   

Try it and you'll be pleasantly surprised.
CERN do much better than you speculate (White Rabbit project)

Also keep in mind, that in this region of precision, you have to model
your digial circuit partially as analog. Especially taking into account
that you have a a finite rise time, input and output jitter, power supply
noise, signal noise etc pp. All these will limit the precision you will
achieve for single measurements.

   
Yes, but in practice is easy to achieve hitter about 2-3 orders of 
magnitude lower than your speculation in a DDMTD.

Attila Kinali

   

Bruce

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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread EWKehren
It is a circuit that they for instance use in the 2110 where they take the  
reference input in case of 10 MHz divide by 2 and also divide the 5 MHz 
down to  500 Hz use an exor and out comes 5.000500 MHz filtered and divided by 
5. The  result is 1.000100 MHz which is mixed with the unknown divided to 1 
MHz. The  result is 100 Hz counted with a 100 MHz period counter and you 
have 1 E 12 in a  second. My counter which is part of the system and thanks to 
Richard MCC is a  PIC, has 0.1, 1, 10 and 100 seconds gate time. The 100 or 
200 MHz are generated  from the reference channel. All logic is in a 
MAX3000A G/A. The output is RS 232  and can also be stored on a USB memory 
stick, 
no PC needed. Austron uses a Xtal  as a filter and I use 2 because I do not 
have access to their Xtal but it works.  A nicer solution would be to use an 
AD 9833 DDS but it would require an   additional PIC to do the math since 
the DDS can not produce an exact 1.000100  MHz. If some one is willing to do 
that chip please contact me off list.
Bert Kehren
 
 
In a message dated 4/20/2012 6:56:14 A.M. Eastern Daylight Time,  
att...@kinali.ch writes:

Moin

On Thu, 19 Apr 2012 18:18:24 -0400  (EDT)
ewkeh...@aol.com wrote:

 I have quite a collection of  equipment and have build Dual Mixer, PICTIC 
 
 and what I think is  best for you a circuit I call the Austron circuit.

What is this  Austron Circuit? And how does it look like? :-)

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] Question about precise frequency / phase measurement

2012-04-20 Thread ed breya
You may want to look at how that was done many years ago with 
frequency difference multiplication as in the old Tracor meters - I 
think the 528 was the main one. They synthesized a 9 MHz reference 
from one input, and then subtracted it from the other to get a 1 MHz 
result, which was used as a reference for another 10 MHz PL 
oscillator. The 9 MHz was subtracted from this, and so on to a next 
identical stage. The net result is that each stage of this process 
multiplies the frequency difference by ten times. These can be 
cascaded until you reach the limit of the noise performance of the 
stage designs - they managed around 10,000 times fairly readily. This 
method can be duplicated fairly easily with modern logic parts. With 
a setup like this you can produce a 1 or 10 MHz carrier that can be 
counted to very high resolution at one second gating - you just 
ignore the carrier digits and look at the multiplied difference 
frequency digits. Or, you can subtract the carrier and get just the 
multiplied difference - but you have to keep track of the phase info 
to know if it's plus or minus.


It's of course possible to use whatever frequencies and stage 
multiplication factors you want, but the tradeoffs are in making the 
numbers come out rationally (especially if you want a number of 
decade multiplier ranges), and the precision and quality of the 
intermediate frequency filtering and processing. About ten to one 
hundred times per stage is within reason. For example, I have an 
experimental (way unfinished) setup started with three stages of 1 
GHz PLOs for multiplication, and a 990 MHz reference. This will give 
100X per stage, reaching 10E6 difference frequency multiplication at 
one second gating, presuming I can manage the phase noise 
sufficiently. A quick two-stage setup indicated no problem reaching 
10E4, but that last 100X will be tricky - I have to build it up for 
real first, with extremely clean power supplies, shielded signal 
processing modules, and solid signal routing, just to see if it's 
possible. I would not recommend this approach - I'm only doing it 
because I happened to have all the main parts on hand. It would be 
better to keep everything down to 100 MHz or less for processing in 
ECL or ACMOS, and using crystal VCOs and filters.


Ed


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread EWKehren
I have and use a Tracor 527E how ever the Austron circuit including counter 
 is a PCB board 2.2 X 2.5 inches and I have not seen a Tracor for $ 50. I 
think I  paid $ 800 fifteen years ago. 
Bert Kehren
 
 
In a message dated 4/20/2012 11:37:16 A.M. Eastern Daylight Time,  
e...@telight.com writes:

You may  want to look at how that was done many years ago with 
frequency difference  multiplication as in the old Tracor meters - I 
think the 528 was the main  one. They synthesized a 9 MHz reference 
from one input, and then  subtracted it from the other to get a 1 MHz 
result, which was used as a  reference for another 10 MHz PL 
oscillator. The 9 MHz was subtracted from  this, and so on to a next 
identical stage. The net result is that each  stage of this process 
multiplies the frequency difference by ten times.  These can be 
cascaded until you reach the limit of the noise performance  of the 
stage designs - they managed around 10,000 times fairly readily.  This 
method can be duplicated fairly easily with modern logic parts. With  
a setup like this you can produce a 1 or 10 MHz carrier that can be  
counted to very high resolution at one second gating - you just 
ignore  the carrier digits and look at the multiplied difference 
frequency digits.  Or, you can subtract the carrier and get just the 
multiplied difference -  but you have to keep track of the phase info 
to know if it's plus or  minus.

It's of course possible to use whatever frequencies and stage  
multiplication factors you want, but the tradeoffs are in making the  
numbers come out rationally (especially if you want a number of 
decade  multiplier ranges), and the precision and quality of the 
intermediate  frequency filtering and processing. About ten to one 
hundred times per  stage is within reason. For example, I have an 
experimental (way  unfinished) setup started with three stages of 1 
GHz PLOs for  multiplication, and a 990 MHz reference. This will give 
100X per stage,  reaching 10E6 difference frequency multiplication at 
one second gating,  presuming I can manage the phase noise 
sufficiently. A quick two-stage  setup indicated no problem reaching 
10E4, but that last 100X will be  tricky - I have to build it up for 
real first, with extremely clean power  supplies, shielded signal 
processing modules, and solid signal routing,  just to see if it's 
possible. I would not recommend this approach - I'm  only doing it 
because I happened to have all the main parts on hand. It  would be 
better to keep everything down to 100 MHz or less for processing  in 
ECL or ACMOS, and using crystal VCOs and  filters.

Ed


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread EWKehren
Ed
 at one time I used two 9 GHz multiplier chains out of FTS 4000's  mixed 
them, if you are interested contact me off list I may still have them.  Have 
thrown out many things because I am downsizing in preparation for a  move.
Bert
 
 
In a message dated 4/20/2012 11:37:16 A.M. Eastern Daylight Time,  
e...@telight.com writes:

You may  want to look at how that was done many years ago with 
frequency difference  multiplication as in the old Tracor meters - I 
think the 528 was the main  one. They synthesized a 9 MHz reference 
from one input, and then  subtracted it from the other to get a 1 MHz 
result, which was used as a  reference for another 10 MHz PL 
oscillator. The 9 MHz was subtracted from  this, and so on to a next 
identical stage. The net result is that each  stage of this process 
multiplies the frequency difference by ten times.  These can be 
cascaded until you reach the limit of the noise performance  of the 
stage designs - they managed around 10,000 times fairly readily.  This 
method can be duplicated fairly easily with modern logic parts. With  
a setup like this you can produce a 1 or 10 MHz carrier that can be  
counted to very high resolution at one second gating - you just 
ignore  the carrier digits and look at the multiplied difference 
frequency digits.  Or, you can subtract the carrier and get just the 
multiplied difference -  but you have to keep track of the phase info 
to know if it's plus or  minus.

It's of course possible to use whatever frequencies and stage  
multiplication factors you want, but the tradeoffs are in making the  
numbers come out rationally (especially if you want a number of 
decade  multiplier ranges), and the precision and quality of the 
intermediate  frequency filtering and processing. About ten to one 
hundred times per  stage is within reason. For example, I have an 
experimental (way  unfinished) setup started with three stages of 1 
GHz PLOs for  multiplication, and a 990 MHz reference. This will give 
100X per stage,  reaching 10E6 difference frequency multiplication at 
one second gating,  presuming I can manage the phase noise 
sufficiently. A quick two-stage  setup indicated no problem reaching 
10E4, but that last 100X will be  tricky - I have to build it up for 
real first, with extremely clean power  supplies, shielded signal 
processing modules, and solid signal routing,  just to see if it's 
possible. I would not recommend this approach - I'm  only doing it 
because I happened to have all the main parts on hand. It  would be 
better to keep everything down to 100 MHz or less for processing  in 
ECL or ACMOS, and using crystal VCOs and  filters.

Ed


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread WarrenS
Wolfgang asked

Does anybody know a possibility to get a resolution  1 mHz ? (in 1 second)
 The goal is look for frequency deviations caused by external influences ...

A silly question to ask time nuts. :)
How good do you really want it to be?
1 mHz out of 10 MHz in one second is only 1 part in 1e-10 and needs a 
resolution of  0.1 ns
 
For a high end example showing external influences causing small freq 
variation, see the swinging OSC test  at
http://www.thegleam.com/ke5fx/tpll/swing.gif 
This has a resolution of ~0.01 mHz (1e-12) at ~100 Hz update rate, which is 
about 10K better than what you have asked for. 


Many of the high end suggestions you are getting is how to do it 100 plus times 
better than what you've asked for.
Yes, plain old HC parts and some care can get you resolution and repeatability 
below 0.1 ns when averaging for one second.

For something pretty simple, see Bruce's XOR Linear Phase detector page at,  
http://www.ko4bb.com/~bruce/LinearPhaseComparators.html
I made a version of that using 74AHCxx parts that gives ~1 mHz freq difference 
resolution at 100 Hz update rate.

For really high end, simple, low cost, with no digital parts,  there is a 2.0 
version of the TPLL with resolution of 1e-14/sec.
That is capable of near 1mHz resolution with an update rate of 10K/sec.
Information on TPLL version 1 is at  http://www.ke5fx.com/tpll.htm

ws


snip

I want to monitor the frequency deviation continuously (that means: i 
don't want to look at a scope ;) and log the data several times per second. 
The goal is not to make a  'quality test' of the oscillator,
but to look for frequency deviations which are caused by external 
influences of various kind.

The question is, if 74HCxx parts would be good enough to get  1 mHz 
resolution for a 10 MHz frequency with an update rate of  1 sec.

Regards,
   Wolfgang



Hello @all,

my name is Wolfgang and i'm new to the list.  :)

I browsed through the list archive, but i didn't find the infos i need, 
so i decided to join the list and to ask the experts directly.  :)

I want to measure the frequency difference between a 10 MHz OCXO and a 
10 MHz Rubidium.
I think that's what many people here have done many times... but i don't 
want to use expensive
equipment like time interval counters with picosecond resolution etc. I 
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1 
measurement per second, or even more.

My first approach was to use a simple XOR phase comparator. I tried a 
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz 
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or 
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them. 
Another problem is that the
difference frequency gets very low when the frequencies are very close, 
so it's not enough to look
only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?

Best regards,
   Wolfgang
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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread Jim Hickstein

On 2012/04/20 13:44, time-nuts-requ...@febo.com wrote:

For a high end example showing external influences causing small freq 
variation, see the swinging OSC test  at
http://www.thegleam.com/ke5fx/tpll/swing.gif


Neat!  Is there a page explaining a bit more about it?

I was summarizing the Hafele-Keating experiment to my brother the other day -- 
just bullshitting, really, 'cause I barely know what's going on here myself -- 
so it occurs to me to wonder.  Acceleration is probably the cause, but a 
mechanical effect in the oscillator, something tightened in cockpit?  Surely 
not a relativistic effect.  Not at 18 inches.  (This is where we figure out that 
I grasp the concepts, but can't actually do the problems.)


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-20 Thread ws at Yahoo


No page. The effect is nothing very special. No relativity.
Mostly just the effect of the oscillator's G sensitivity caused by tilting 
and acceleration as it swings.

What is generally measured with a 2 G static turn over test.
The thing about the test is that it gives a signal that is very hard to 
measure and a wave form shape that is easy to verify.
This shows how good the TPLL is at detecting small frequency changes very 
quickly.
The TPLL2.0 gives the best results for that test that I've seen from any 
instrument.


ws


On 2012/04/20 13:44, time-nuts-request at febo.com wrote:
For a high end example showing external influences causing small freq 
variation, see the swinging OSC test  at

http://www.thegleam.com/ke5fx/tpll/swing.gif


Neat!  Is there a page explaining a bit more about it?

I was summarizing the Hafele-Keating experiment to my brother the other 
day -- 
just bullshitting, really, 'cause I barely know what's going on here 
myself -- 
so it occurs to me to wonder.  Acceleration is probably the cause, but a
mechanical effect in the oscillator, something tightened in cockpit? 
Surely
not a relativistic effect.  Not at 18 inches.  (This is where we figure out 
that
I grasp the concepts, but can't actually do the problems.) 



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[time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread skywatcher

Hello @all,

my name is Wolfgang and i'm new to the list.  :)

I browsed through the list archive, but i didn't find the infos i need, 
so i decided to join the list

and to ask the experts directly.  :)

I want to measure the frequency difference between a 10 MHz OCXO and a 
10 MHz Rubidium.
I think that's what many people here have done many times... but i don't 
want to use expensive
equipment like time interval counters with picosecond resolution etc. I 
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1 
measurement per second,

or even more.

My first approach was to use a simple XOR phase comparator. I tried a 
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz 
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or 
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them. 
Another problem is that the
difference frequency gets very low when the frequencies are very close, 
so it's not enough to look

only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?

Best regards,
  Wolfgang


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread lists
Just a speculation on my part, but if you got some non-saturating logic like 
ECL, the jitter would be less. 

I haven't done any ECL in years, but the traces I got from ECL circuits are 
amazingly clean. I was evaluating a competitions ECL DAC. 
-Original Message-
From: skywatcher skywatc...@web.de
Sender: time-nuts-boun...@febo.com
Date: Thu, 19 Apr 2012 21:10:03 
To: time-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: [time-nuts] Question about precise frequency / phase measurement

Hello @all,

my name is Wolfgang and i'm new to the list.  :)

I browsed through the list archive, but i didn't find the infos i need, 
so i decided to join the list
and to ask the experts directly.  :)

I want to measure the frequency difference between a 10 MHz OCXO and a 
10 MHz Rubidium.
I think that's what many people here have done many times... but i don't 
want to use expensive
equipment like time interval counters with picosecond resolution etc. I 
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1 
measurement per second,
or even more.

My first approach was to use a simple XOR phase comparator. I tried a 
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz 
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or 
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them. 
Another problem is that the
difference frequency gets very low when the frequencies are very close, 
so it's not enough to look
only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?

Best regards,
   Wolfgang


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread J. Forster
Welcome,

 Hello @all,

 my name is Wolfgang and i'm new to the list.  :)

 I browsed through the list archive, but i didn't find the infos i need,
 so i decided to join the list
 and to ask the experts directly.  :)

 I want to measure the frequency difference between a 10 MHz OCXO and a
 10 MHz Rubidium.
 I think that's what many people here have done many times... but i don't
 want to use expensive
 equipment like time interval counters with picosecond resolution etc. I
 would prefer a cheap and
 easy solution. I also would like to have an update rate of more than 1
 measurement per second,
 or even more.

 My first approach was to use a simple XOR phase comparator. I tried a
 74HCT86 and a 74HCT4046.
 It works, but it's very noisy, so i don't get better than about 10 mHz
 frequency resolution.
 If i look at the lowpass-filtered output i don't see a nice sine or
 triangular wave, but it looks more
 than a triangular wave with round tops and some bumps between them.

You would only see a sine wave if the difference frequency was stable an
such that the LPF cut off all but the fundamental.

If you want sine wave output, use an analog mixer on sine waves, and don't
overdrive it.

-John

===

 Another problem is that the
 difference frequency gets very low when the frequencies are very close,
 so it's not enough to look
 only for zero crossings of the difference signal.

 Does anybody know a possibility to get a resolution  1 mHz ?

 Best regards,
Wolfgang


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Magnus Danielson

Hi Wolfgang,

On 19/04/12 21:10, skywatcher wrote:

Hello @all,

my name is Wolfgang and i'm new to the list. :)


Welcome!


I want to measure the frequency difference between a 10 MHz OCXO and a
10 MHz Rubidium.
I think that's what many people here have done many times... but i don't
want to use expensive
equipment like time interval counters with picosecond resolution etc. I
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1
measurement per second,
or even more.

My first approach was to use a simple XOR phase comparator. I tried a
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them.
Another problem is that the
difference frequency gets very low when the frequencies are very close,
so it's not enough to look
only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?


Have you looked at the PICTIC II project? It's not too bad.

There is several other possible projects to consider, but the PICTIC II 
may be a good start. Also look at a divide down system such as the TADD 
2 divider or the just released TADD 2 Mini.


There is a challenge in doing fairly high precission for low budget here 
on the list. Besides measuring frequency, we pride ourselves in 
measuring the frequency stability, Allan Deviation (ADEV), as good as 
possible.


Cheers,
Magnus

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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Azelio Boriani
And, if you are measuring, by analog mixing, two very slightly different
frequencies, what do you expect to obtain if not a signal that is slow,
very slow. How can you measure milliHertz or microHertz without waiting?

On Thu, Apr 19, 2012 at 9:31 PM, Magnus Danielson 
mag...@rubidium.dyndns.org wrote:

 Hi Wolfgang,


 On 19/04/12 21:10, skywatcher wrote:

 Hello @all,

 my name is Wolfgang and i'm new to the list. :)


 Welcome!


  I want to measure the frequency difference between a 10 MHz OCXO and a
 10 MHz Rubidium.
 I think that's what many people here have done many times... but i don't
 want to use expensive
 equipment like time interval counters with picosecond resolution etc. I
 would prefer a cheap and
 easy solution. I also would like to have an update rate of more than 1
 measurement per second,
 or even more.

 My first approach was to use a simple XOR phase comparator. I tried a
 74HCT86 and a 74HCT4046.
 It works, but it's very noisy, so i don't get better than about 10 mHz
 frequency resolution.
 If i look at the lowpass-filtered output i don't see a nice sine or
 triangular wave, but it looks more
 than a triangular wave with round tops and some bumps between them.
 Another problem is that the
 difference frequency gets very low when the frequencies are very close,
 so it's not enough to look
 only for zero crossings of the difference signal.

 Does anybody know a possibility to get a resolution  1 mHz ?


 Have you looked at the PICTIC II project? It's not too bad.

 There is several other possible projects to consider, but the PICTIC II
 may be a good start. Also look at a divide down system such as the TADD 2
 divider or the just released TADD 2 Mini.

 There is a challenge in doing fairly high precission for low budget here
 on the list. Besides measuring frequency, we pride ourselves in measuring
 the frequency stability, Allan Deviation (ADEV), as good as possible.

 Cheers,
 Magnus


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread SAIDJACK
Hi Wolfgang,
 
one of the easiest and very accurate ways to do this is simply to measure  
the drift of the two 10MHz signals on an oscilloscope. Adjust the OCXO so  
that this drift between the two traces is as slow as you can get it. Then 
simply  measure it over time. Use one signal for trigger, the other to display 
if  you only have a one channel scope.
 
If you get say 10ns drift over 1 hour (which you can easily measure even  
with the cheapest scopes), that is a resolution of 10ns/3600s = 2.78E012.
 
Or in other words 27.7uHz!
 
This has been discussed before and documented in the time nuts archives  
some time ago.
 
bye,
Said
 
 
 
 
In a message dated 4/19/2012 12:10:53 Pacific Daylight Time,  
skywatc...@web.de writes:

My first  approach was to use a simple XOR phase comparator. I tried a 
74HCT86 and a  74HCT4046.
It works, but it's very noisy, so i don't get better than about  10 mHz 
frequency resolution.
If i look at the lowpass-filtered output i  don't see a nice sine or 
triangular wave, but it looks more
than a  triangular wave with round tops and some bumps between them. 
Another  problem is that the
difference frequency gets very low when the frequencies  are very close, 
so it's not enough to look
only for zero crossings of  the difference signal.

Does anybody know a possibility to get a  resolution  1 mHz ?

Best regards,
Wolfgang



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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Bruce Griffiths
Using a dual mixer time difference system (either the digital dual mixer 
time difference (DDMTD) or the analog variant (DMTD)) can easily achieve 
the required resolution.
The DDMTD is relatively cheap to implement however it requires an offset 
oscillator to beat against the 2 signals being compared.
However a DDMTD can use a 5MHz offset oscillator can be used with 5MHz, 
10MHz, 15MHz ... input signals whereas a DMTD requires a 10MHz offset 
oscillator to be used with 10Mhz input signals.


The DDMTD uses a pair of shift registers clocked by the offset source 
where each of the 2 signals being compared is connected to the data 
inputs of its shift register.
The time difference between beat outputs of the 2 shift registers is 
then measured with relatively low resolution.
Some digital filtering of the shift register output transitions is 
usually required.
A pair of 74HC164's will typically have a equivalent input jitter of 
around 10ps or so, a 74AC164 will be about 4x quieter.


With a 5.55MHz offset oscillator and 10MHz inputs the shift register 
output beat frequency will be 110Hz.


It is usually advantageous to use an FPGA to implement the digital 
filtering, timestamping and even the shift registers (although external 
shift registers will have less crosstalk).


Bruce

skywatcher wrote:

Hello @all,

my name is Wolfgang and i'm new to the list.  :)

I browsed through the list archive, but i didn't find the infos i 
need, so i decided to join the list

and to ask the experts directly.  :)

I want to measure the frequency difference between a 10 MHz OCXO and a 
10 MHz Rubidium.
I think that's what many people here have done many times... but i 
don't want to use expensive
equipment like time interval counters with picosecond resolution etc. 
I would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1 
measurement per second,

or even more.

My first approach was to use a simple XOR phase comparator. I tried a 
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz 
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or 
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them. 
Another problem is that the
difference frequency gets very low when the frequencies are very 
close, so it's not enough to look

only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?

Best regards,
  Wolfgang


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Azelio Boriani
Yes, and, as you can see, you have to wait 1 hour.

On Thu, Apr 19, 2012 at 9:49 PM, saidj...@aol.com wrote:

 Hi Wolfgang,

 one of the easiest and very accurate ways to do this is simply to measure
 the drift of the two 10MHz signals on an oscilloscope. Adjust the OCXO so
 that this drift between the two traces is as slow as you can get it. Then
 simply  measure it over time. Use one signal for trigger, the other to
 display
 if  you only have a one channel scope.

 If you get say 10ns drift over 1 hour (which you can easily measure even
 with the cheapest scopes), that is a resolution of 10ns/3600s = 2.78E012.

 Or in other words 27.7uHz!

 This has been discussed before and documented in the time nuts archives
 some time ago.

 bye,
 Said




 In a message dated 4/19/2012 12:10:53 Pacific Daylight Time,
 skywatc...@web.de writes:

 My first  approach was to use a simple XOR phase comparator. I tried a
 74HCT86 and a  74HCT4046.
 It works, but it's very noisy, so i don't get better than about  10 mHz
 frequency resolution.
 If i look at the lowpass-filtered output i  don't see a nice sine or
 triangular wave, but it looks more
 than a  triangular wave with round tops and some bumps between them.
 Another  problem is that the
 difference frequency gets very low when the frequencies  are very close,
 so it's not enough to look
 only for zero crossings of  the difference signal.

 Does anybody know a possibility to get a  resolution  1 mHz ?

 Best regards,
 Wolfgang



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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Bruce Griffiths

Use a dual mixer system with an offset LO.

Bruce

Azelio Boriani wrote:

And, if you are measuring, by analog mixing, two very slightly different
frequencies, what do you expect to obtain if not a signal that is slow,
very slow. How can you measure milliHertz or microHertz without waiting?

On Thu, Apr 19, 2012 at 9:31 PM, Magnus Danielson
mag...@rubidium.dyndns.org  wrote:

   

Hi Wolfgang,


On 19/04/12 21:10, skywatcher wrote:

 

Hello @all,

my name is Wolfgang and i'm new to the list. :)

   

Welcome!


  I want to measure the frequency difference between a 10 MHz OCXO and a
 

10 MHz Rubidium.
I think that's what many people here have done many times... but i don't
want to use expensive
equipment like time interval counters with picosecond resolution etc. I
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1
measurement per second,
or even more.

My first approach was to use a simple XOR phase comparator. I tried a
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them.
Another problem is that the
difference frequency gets very low when the frequencies are very close,
so it's not enough to look
only for zero crossings of the difference signal.

Does anybody know a possibility to get a resolution  1 mHz ?

   

Have you looked at the PICTIC II project? It's not too bad.

There is several other possible projects to consider, but the PICTIC II
may be a good start. Also look at a divide down system such as the TADD 2
divider or the just released TADD 2 Mini.

There is a challenge in doing fairly high precission for low budget here
on the list. Besides measuring frequency, we pride ourselves in measuring
the frequency stability, Allan Deviation (ADEV), as good as possible.

Cheers,
Magnus


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Azelio Boriani
Of course, there are PICTIC II, DMTD, DDMTD, SR620, HP5370B, Wavecrest,
PM6681, HP53132. The simplest is using a scope and... wait.

On Thu, Apr 19, 2012 at 9:53 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz
 wrote:

 Use a dual mixer system with an offset LO.

 Bruce

 Azelio Boriani wrote:

 And, if you are measuring, by analog mixing, two very slightly different
 frequencies, what do you expect to obtain if not a signal that is slow,
 very slow. How can you measure milliHertz or microHertz without waiting?

 On Thu, Apr 19, 2012 at 9:31 PM, Magnus Danielson
 mag...@rubidium.dyndns.org  wrote:



 Hi Wolfgang,



 On 19/04/12 21:10, skywatcher wrote:



 Hello @all,

 my name is Wolfgang and i'm new to the list. :)



 Welcome!



  I want to measure the frequency difference between a 10 MHz OCXO and a


 10 MHz Rubidium.
 I think that's what many people here have done many times... but i don't
 want to use expensive
 equipment like time interval counters with picosecond resolution etc. I
 would prefer a cheap and
 easy solution. I also would like to have an update rate of more than 1
 measurement per second,
 or even more.

 My first approach was to use a simple XOR phase comparator. I tried a
 74HCT86 and a 74HCT4046.
 It works, but it's very noisy, so i don't get better than about 10 mHz
 frequency resolution.
 If i look at the lowpass-filtered output i don't see a nice sine or
 triangular wave, but it looks more
 than a triangular wave with round tops and some bumps between them.
 Another problem is that the
 difference frequency gets very low when the frequencies are very close,
 so it's not enough to look
 only for zero crossings of the difference signal.

 Does anybody know a possibility to get a resolution  1 mHz ?



 Have you looked at the PICTIC II project? It's not too bad.

 There is several other possible projects to consider, but the PICTIC II
 may be a good start. Also look at a divide down system such as the TADD 2
 divider or the just released TADD 2 Mini.

 There is a challenge in doing fairly high precission for low budget here
 on the list. Besides measuring frequency, we pride ourselves in measuring
 the frequency stability, Allan Deviation (ADEV), as good as possible.

 Cheers,
 Magnus



 ___
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 To unsubscribe, go to
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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread skywatcher

Hi Bruce,

this sounds very good, and seems to fit my requirements quite well.  :)
I will have a closer look to this concept.

I also had the idea to take the reference frequency, divide it, and mix 
the division result again with the reference
to get an offset to the reference frequency which would give a higher 
beat frequency which allows a reasonable measurement rate.
But it didn't turn out as i expected, because there was a lot of 
'garbage' in the signals.


Best regards,
  Wolfgang


Am 19.04.2012 21:51, schrieb Bruce Griffiths:
Using a dual mixer time difference system (either the digital dual 
mixer time difference (DDMTD) or the analog variant (DMTD)) can easily 
achieve the required resolution.
The DDMTD is relatively cheap to implement however it requires an 
offset oscillator to beat against the 2 signals being compared.
However a DDMTD can use a 5MHz offset oscillator can be used with 
5MHz, 10MHz, 15MHz ... input signals whereas a DMTD requires a 10MHz 
offset oscillator to be used with 10Mhz input signals.


The DDMTD uses a pair of shift registers clocked by the offset source 
where each of the 2 signals being compared is connected to the data 
inputs of its shift register.
The time difference between beat outputs of the 2 shift registers is 
then measured with relatively low resolution.
Some digital filtering of the shift register output transitions is 
usually required.
A pair of 74HC164's will typically have a equivalent input jitter of 
around 10ps or so, a 74AC164 will be about 4x quieter.


With a 5.55MHz offset oscillator and 10MHz inputs the shift 
register output beat frequency will be 110Hz.


It is usually advantageous to use an FPGA to implement the digital 
filtering, timestamping and even the shift registers (although 
external shift registers will have less crosstalk).


Bruce



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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread SAIDJACK
Depends on the scope..
 
if your scope has 100ps A-to-B measurement resolution, then waiting 5  
minutes in this scenario would give 0.83ns drift, with 100ps uncertainty IF 
your 
 oscillators were synced to ~3ppt which is very tough to do with a 
free-running  OCXO (It would be unrealistic to get that stability from the two 
sources if they  are free running).
 
A more realistic scenario would give say 100ns drift in 5 minutes, then a  
0.1ns resolution on the scope would give a very accurate reading in just 5  
minutes (100ns +/-0.1ns = +/-0.1% error). The result would be 3.33E-010,  
+/-3.33E-013. Who needs more resolution than that as the OCXO will likely 
wander  much more than that in 5 minutes..
 
bye,
Said
 
 
In a message dated 4/19/2012 12:52:07 Pacific Daylight Time,  
azelio.bori...@screen.it writes:

Yes,  and, as you can see, you have to wait 1 hour.

On Thu, Apr 19, 2012 at  9:49 PM, saidj...@aol.com wrote:

 Hi  Wolfgang,

 one of the easiest and very accurate ways to do this  is simply to measure
 the drift of the two 10MHz signals on an  oscilloscope. Adjust the OCXO so
 that this drift between the two  traces is as slow as you can get it. Then
 simply  measure it over  time. Use one signal for trigger, the other to
 display
  if  you only have a one channel scope.

 If you get say  10ns drift over 1 hour (which you can easily measure even
 with the  cheapest scopes), that is a resolution of 10ns/3600s =  
2.78E012.

 Or in other words 27.7uHz!

 This has  been discussed before and documented in the time nuts archives
 some  time ago.

 bye,
  Said


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread EWKehren
Wolfgang
It would help if you would let us know what equipment other than a scope  
you have. Also what resolution you would want to achieve. One time set up  or 
want to use repeatedly.
Bert Kehren 
 
 
In a message dated 4/19/2012 4:53:40 P.M. Eastern Daylight Time,  
saidj...@aol.com writes:

Depends  on the scope..

if your scope has 100ps A-to-B measurement resolution,  then waiting 5  
minutes in this scenario would give 0.83ns drift,  with 100ps uncertainty 
IF your 
oscillators were synced to ~3ppt which is  very tough to do with a 
free-running  OCXO (It would be unrealistic  to get that stability from the 
two 
sources if they  are free  running).

A more realistic scenario would give say 100ns drift in 5  minutes, then a  
0.1ns resolution on the scope would give a very  accurate reading in just 5 
 
minutes (100ns +/-0.1ns = +/-0.1% error).  The result would be 3.33E-010,  
+/-3.33E-013. Who needs more  resolution than that as the OCXO will likely 
wander  much more than  that in 5 minutes..

bye,
Said


In a message dated  4/19/2012 12:52:07 Pacific Daylight Time,  
azelio.bori...@screen.it  writes:

Yes,  and, as you can see, you have to wait 1  hour.

On Thu, Apr 19, 2012 at  9:49 PM, saidj...@aol.com  wrote:

 Hi  Wolfgang,

 one of the easiest and  very accurate ways to do this  is simply to 
measure
 the drift of  the two 10MHz signals on an  oscilloscope. Adjust the OCXO 
so
  that this drift between the two  traces is as slow as you can get it.  
Then
 simply  measure it over  time. Use one signal for  trigger, the other to
 display
  if  you only have a  one channel scope.

 If you get say  10ns drift over 1 hour  (which you can easily measure even
 with the  cheapest scopes),  that is a resolution of 10ns/3600s =  
2.78E012.

 Or in  other words 27.7uHz!

 This has  been discussed before and  documented in the time nuts archives
 some  time  ago.

 bye,
   Said


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread skywatcher

Hi Bert

I want to monitor the frequency deviation continuously (that means: i 
don't want to look at a scope ;)
and log the data several times per second. The goal is not to make a 
'quality test' of the oscillator,
but to look for frequency deviations which are caused by external 
influences of various kind.


I have a digital 500 MS scope, so i can use this for circuit 
development, but i don't want to use it
for the actual measurements. Time measurements with microsecond accuracy 
can be done
with a microcontroller, that's not a problem.  BTW i'm using the 
Parallax 'Propeller' controller
which has 8 cores running at 80 MHz each, and can measure time intervals 
with 12.5 ns resolution.
It has also some very interesting timing circuitry, and can even 
generate VGA video signals with
user-defined timing without any external special components. May be of 
interest for one or the other

here on the list.  :)
For those who are interested:  
http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/Propeller-P8X32A-Datasheet-v1.4.0.pdf


I think the DDMTD could be a good solution.  The question is, if 74HCxx 
parts would be good enough
to get  1 mHz resolution for a 10 MHz frequency with an update rate of 
 1 sec.
Can i use a 74HCT4046 PLL for the 'helper PLL' or is this one not good 
enough ?


Maybe i will do some tests next weekend to see what i can achieve with 
these 74HC parts, before

looking for better ones...

Regards,
  Wolfgang


Am 19.04.2012 23:14, schrieb ewkeh...@aol.com:

Wolfgang
It would help if you would let us know what equipment other than a scope
you have. Also what resolution you would want to achieve. One time set up  or
want to use repeatedly.
Bert Kehren





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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread Joseph M Gwinn

The traditional approach was to use a double-balanced mixer configured as a
phase detector, pass the phase detector output through a low-pass filter
(with 1 Hz bandwidth), and plot the result using a chart recorder.  The
chart recorder would also have marks from some kind of accurate clock.
After a few days of recording, the beat frequency is easily determined, as
is variations over the day.  The present-day equivalent replaces the chart
recorder with a recording digital voltmeter of some kind.

Joe Gwinn




From:   Azelio Boriani azelio.bori...@screen.it
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Date:   04/19/2012 03:38 PM
Subject:Re: [time-nuts] Question about precise frequency / phase
measurement
Sent by:time-nuts-boun...@febo.com



And, if you are measuring, by analog mixing, two very slightly different
frequencies, what do you expect to obtain if not a signal that is slow,
very slow. How can you measure milliHertz or microHertz without waiting?

On Thu, Apr 19, 2012 at 9:31 PM, Magnus Danielson 
mag...@rubidium.dyndns.org wrote:

 Hi Wolfgang,


 On 19/04/12 21:10, skywatcher wrote:

 Hello @all,

 my name is Wolfgang and i'm new to the list. :)


 Welcome!


  I want to measure the frequency difference between a 10 MHz OCXO and a
 10 MHz Rubidium.
 I think that's what many people here have done many times... but i don't
 want to use expensive
 equipment like time interval counters with picosecond resolution etc. I
 would prefer a cheap and
 easy solution. I also would like to have an update rate of more than 1
 measurement per second,
 or even more.

 My first approach was to use a simple XOR phase comparator. I tried a
 74HCT86 and a 74HCT4046.
 It works, but it's very noisy, so i don't get better than about 10 mHz
 frequency resolution.
 If i look at the lowpass-filtered output i don't see a nice sine or
 triangular wave, but it looks more
 than a triangular wave with round tops and some bumps between them.
 Another problem is that the
 difference frequency gets very low when the frequencies are very close,
 so it's not enough to look
 only for zero crossings of the difference signal.

 Does anybody know a possibility to get a resolution  1 mHz ?


 Have you looked at the PICTIC II project? It's not too bad.

 There is several other possible projects to consider, but the PICTIC II
 may be a good start. Also look at a divide down system such as the TADD 2
 divider or the just released TADD 2 Mini.

 There is a challenge in doing fairly high precission for low budget here
 on the list. Besides measuring frequency, we pride ourselves in measuring
 the frequency stability, Allan Deviation (ADEV), as good as possible.

 Cheers,
 Magnus


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Re: [time-nuts] Question about precise frequency / phase measurement

2012-04-19 Thread EWKehren
Wolfgang
I have quite a collection of equipment and have build Dual Mixer, PICTIC  
and what I think is best for you a circuit I call the Austron circuit. For 
less  than $ 50 you can have a standalone system that gives you a RS 232 
output with 1  E 12 resolution in 1 second, the PIC has 0.1, 1, 10 and 100 
second 
gate  time. At 100 seconds you get 1 E 14. The circuit does use a two stage 
Xtal  filter which is the most difficult part of the circuit. How ever a 
DDS could be  used, but the DDS does not give you 1.000100 MHz with 14 digit 
accuracy so post  processing would be needed. If you have uProcessor 
expertise that would be  perfect way to eliminate the filter part, making it 
even 
lower cost and much  simpler. 
Never did a DDMTD so I do not know how it compares. If you are interested  
contact me off list and I send you all information.
Bert Kehren
 
 
In a message dated 4/19/2012 5:41:08 P.M. Eastern Daylight Time,  
skywatc...@web.de writes:

Hi  Bert

I want to monitor the frequency deviation continuously (that  means: i 
don't want to look at a scope ;)
and log the data several  times per second. The goal is not to make a 
'quality test' of the  oscillator,
but to look for frequency deviations which are caused by  external 
influences of various kind.

I have a digital 500 MS scope,  so i can use this for circuit 
development, but i don't want to use  it
for the actual measurements. Time measurements with microsecond accuracy  
can be done
with a microcontroller, that's not a problem.  BTW i'm  using the 
Parallax 'Propeller' controller
which has 8 cores running at  80 MHz each, and can measure time intervals 
with 12.5 ns resolution.
It  has also some very interesting timing circuitry, and can even 
generate VGA  video signals with
user-defined timing without any external special  components. May be of 
interest for one or the other
here on the  list.  :)
For those who are interested:   
http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/Propeller-P8X32A-
Datasheet-v1.4.0.pdf

I  think the DDMTD could be a good solution.  The question is, if 74HCxx  
parts would be good enough
to get  1 mHz resolution for a 10 MHz  frequency with an update rate of 
 1 sec.
Can i use a 74HCT4046 PLL  for the 'helper PLL' or is this one not good 
enough ?

Maybe i will  do some tests next weekend to see what i can achieve with 
these 74HC  parts, before
looking for better ones...

Regards,
Wolfgang


Am 19.04.2012 23:14, schrieb ewkeh...@aol.com:
  Wolfgang
 It would help if you would let us know what equipment other  than a scope
 you have. Also what resolution you would want to achieve.  One time set 
up  or
 want to use repeatedly.
 Bert  Kehren




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