Re: [time-nuts] Phase measurement of my GPSDO

[Bob kb8tq]

Hi


> On Apr 13, 2020, at 7:18 PM, Taka Kamiya via time-nuts 
>  wrote:
> 
> I am working on pretty much the same thing.  My HP105B has an HP11801 inside. 
>  There is no telling how long it has been off.  Frequency wandered ALL OVER 
> THE PLACE.  It took 2 months of continuous operation to settle down and just 
> do the normal aging/drifting.  

Which edge comes first? 

There’s no way to know the answer to that. The counter very much wants 
to have the “first edge” on the start and the “next edge” on stop. 

Bob

> 
> I have a same question as you do.  How come not just one HP5335?  Your test 
> setup has two output.  One goes to start, the other goes to stop.  Measure 
> the time interval.  Isn't that the goal?
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq  
> wrote:  
> 
> Hi
> 
>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess  wrote:
>> 
>> Hi Bob
>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
>> 
>> Maybe I have some good OpAmps for this purpose in my box. I will try it! of
> 
> You need something that is quiet (like the OP-37) and has a pretty good slew
> rate. Past that, there are a lot of candidates. The TI OPA-228 family is one. 
> 
>> course I saw that my setup was not ideal as there was a bit of noise on the
>> signals which I guess does lead to some jitter in the trigger circuit and
>> therefore decreases my measurement noise floor.
> 
> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good 
> digits. 
> Net result is a measurement that’s good in the vicinity of parts in 10^-13
> 
>> 
>> Can you say something about how it would be done using a TIC?
>> I don't have two identically good counters, but the HP 5335A could be used
>> as TIC, couldn't it.
> 
> The standard way of doing the test is to run two counters / two TIC/s / two 
> whatever’s.
> I know of no practical way to do it with a single 5335.
> 
>> 
>> And the offset source I used is not directly the HP 10811, but the HP 8663A
>> Signal generator internally uses a 10811 as reference source. But I didn't
>> wait for days for it to warm up properly. (Should I?)
> 
> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how you
> use the 10811, it needs to be on for a while. How long very much depends on 
> just how long it’s been off. Best to keep it on all the time. 
> 
>> 
>>> Fun !!!
>> Yea, of course! :-)
>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
>> myself. I use TimeLab to see what numbers I should expect, and then I want
>> to compute it all myself in Matlab because I want to see how it actually
>> works. ;-)
> 
> Be careful any time you code this stuff for the first time. It’s amazingly 
> easy 
> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
> you should not code it up yourself. I generally do it in Excel or in C. 
> 
> Bob
> 
>> 
>> 
>> Best
>> Tobias
>> 
>> 
>> 
>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
>> 
>>> Hi
>>> 
>>> Ok, first the math:
>>> 
>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>>> 
>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>>> 
>>> You get to add a 6 to what Time Lab shows you.
>>> 
>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>>> gets you to 1x10^-10
>>> 
>>> So, what’s going on?
>>> 
>>> You can’t feed the mixer outputs straight into a counter. The counter
>>> front
>>> end does not handle LF audio sine waves very well. You need to do an
>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>>> similar)
>>> should do the trick.
>>> 
>>> Second, the offset source needs to be pretty good. A 10811 tuned high with
>>> both the mechanical trim and the EFC is a pretty good choice to start out.
>>> 
>>> If you only have one counter, simply ignore the second channel. You are now
>>> running a single mixer. It still works as a comparison between the offset
>>> oscillator
>>> and your DUT.
>>> 
>>> If you want to do it properly as a DMTD, then you set up two counters. One
>>> to measure mixer A and the other to measure mixer B.  Set them both up to
>>> measure frequency. Time tag the data files so you know which reading
>>> matches up with which.
>>> 
>>> Fun !!!
>>> 
>>> Bob
>>> 
 On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
 
 Hi again Bob
 
 I tried to do some measurements with a DMTD!
 In my junk box I found a little PCB from earlier experiments on that
>>> topic,
 with a power splitter and two SRA-3H mixers, it was even already wired
>>> for
 the DMTD configuration. So I gave it a try!
 As "transfer oscillator" I used my HP 8663A signal generator, and set it
 high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
 signals and at the mixer outputs, I put a little lowpass filter with
>>> 100Hz
 corner frequency.
 The 

Re: [time-nuts] Phase measurement of my GPSDO

[Bob kb8tq]

Hi

The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other. When 
they
do you get a major burp in your data. Bill’s setup is running a time tagger ….

( = It runs an internal time count, each edge gets “labeled” with a precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval Counter 
simply measures the time between edges. That sounds like the same thing, but 
it’s not quite ….) 


> On Apr 13, 2020, at 6:11 PM, Tobias Pluess  wrote:
> 
> Hi Bob
> 
> Riley suggests to use a single TIC
> 
> http://wriley.com/A%20Small%20DMTD%20System.pdf
> 
> when you look at the block diagram Fig. 4, you can see that one TIC allows
> to compare two oscillators.
> I don't know exactly how, though :-)

The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other. When 
they
do you get a major burp in your data. Bill’s setup is running a time tagger ….

> 
> OK and I see your point on the 8663. I will try to use another reference!
> I definitely didn't keep mine on for a long time. I didn't use the signal
> generator for a while now, so it was unplugged for a few months. I assume
> that's far from optimal for the 10811's stability.

Best approach is to mount your reference off on it’s own and just power it. 
That way
you don’t wear out all the guts of a fancy piece of gear.

Bob

> 
> 
> Tobias
> 
> 
> 
> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq,  wrote:
> 
>> Hi
>> 
>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess  wrote:
>>> 
>>> Hi Bob
>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
>>> 
>>> Maybe I have some good OpAmps for this purpose in my box. I will try it!
>> of
>> 
>> You need something that is quiet (like the OP-37) and has a pretty good
>> slew
>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
>> one.
>> 
>>> course I saw that my setup was not ideal as there was a bit of noise on
>> the
>>> signals which I guess does lead to some jitter in the trigger circuit and
>>> therefore decreases my measurement noise floor.
>> 
>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
>> digits.
>> Net result is a measurement that’s good in the vicinity of parts in 10^-13
>> 
>>> 
>>> Can you say something about how it would be done using a TIC?
>>> I don't have two identically good counters, but the HP 5335A could be
>> used
>>> as TIC, couldn't it.
>> 
>> The standard way of doing the test is to run two counters / two TIC/s /
>> two whatever’s.
>> I know of no practical way to do it with a single 5335.
>> 
>>> 
>>> And the offset source I used is not directly the HP 10811, but the HP
>> 8663A
>>> Signal generator internally uses a 10811 as reference source. But I
>> didn't
>>> wait for days for it to warm up properly. (Should I?)
>> 
>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how
>> you
>> use the 10811, it needs to be on for a while. How long very much depends
>> on
>> just how long it’s been off. Best to keep it on all the time.
>> 
>>> 
 Fun !!!
>>> Yea, of course! :-)
>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
>>> myself. I use TimeLab to see what numbers I should expect, and then I
>> want
>>> to compute it all myself in Matlab because I want to see how it actually
>>> works. ;-)
>> 
>> Be careful any time you code this stuff for the first time. It’s amazingly
>> easy
>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
>> you should not code it up yourself. I generally do it in Excel or in C.
>> 
>> Bob
>> 
>>> 
>>> 
>>> Best
>>> Tobias
>>> 
>>> 
>>> 
>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
>>> 
 Hi
 
 Ok, first the math:
 
 If your offset oscillator is 10 Hz high at 10 MHz, you have a:
 
 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
 
 You get to add a 6 to what Time Lab shows you.
 
 If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
 gets you to 1x10^-10
 
 So, what’s going on?
 
 You can’t feed the mixer outputs straight into a counter. The counter
 front
 end does not handle LF audio sine waves very well. You need to do an
 op-amp based limiter. A pair of OP-37’s in each leg ( or something
 similar)
 should do the trick.
 
 Second, the offset source needs to be pretty good. A 10811 tuned high
>> with
 both the mechanical trim and the EFC is a pretty good choice to start
>> out.
 
 If you only have one counter, simply ignore the second channel. You are
>> now
 running a single mixer. It still works as a comparison between the
>> offset
 oscillator
 and your DUT.
 
 If you want to do it properly as a DMTD, then you set up two counters.
>> One
 to measure mixer A and the other to measure 

Re: [time-nuts] Phase measurement of my GPSDO

[Taka Kamiya via time-nuts]

I am working on pretty much the same thing.  My HP105B has an HP11801 inside.  
There is no telling how long it has been off.  Frequency wandered ALL OVER THE 
PLACE.  It took 2 months of continuous operation to settle down and just do the 
normal aging/drifting.  

I have a same question as you do.  How come not just one HP5335?  Your test 
setup has two output.  One goes to start, the other goes to stop.  Measure the 
time interval.  Isn't that the goal?

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq  wrote: 
 
 
 Hi

> On Apr 13, 2020, at 5:06 PM, Tobias Pluess  wrote:
> 
> Hi Bob
> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> 
> Maybe I have some good OpAmps for this purpose in my box. I will try it! of

You need something that is quiet (like the OP-37) and has a pretty good slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is one. 

> course I saw that my setup was not ideal as there was a bit of noise on the
> signals which I guess does lead to some jitter in the trigger circuit and
> therefore decreases my measurement noise floor.

Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good digits. 
Net result is a measurement that’s good in the vicinity of parts in 10^-13

> 
> Can you say something about how it would be done using a TIC?
> I don't have two identically good counters, but the HP 5335A could be used
> as TIC, couldn't it.

The standard way of doing the test is to run two counters / two TIC/s / two 
whatever’s.
I know of no practical way to do it with a single 5335.

> 
> And the offset source I used is not directly the HP 10811, but the HP 8663A
> Signal generator internally uses a 10811 as reference source. But I didn't
> wait for days for it to warm up properly. (Should I?)

The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how you
use the 10811, it needs to be on for a while. How long very much depends on 
just how long it’s been off. Best to keep it on all the time. 

> 
>> Fun !!!
> Yea, of course! :-)
> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> myself. I use TimeLab to see what numbers I should expect, and then I want
> to compute it all myself in Matlab because I want to see how it actually
> works. ;-)

Be careful any time you code this stuff for the first time. It’s amazingly easy 
( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
you should not code it up yourself. I generally do it in Excel or in C. 

Bob

> 
> 
> Best
> Tobias
> 
> 
> 
> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> Ok, first the math:
>> 
>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>> 
>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>> 
>> You get to add a 6 to what Time Lab shows you.
>> 
>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>> gets you to 1x10^-10
>> 
>> So, what’s going on?
>> 
>> You can’t feed the mixer outputs straight into a counter. The counter
>> front
>> end does not handle LF audio sine waves very well. You need to do an
>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>> similar)
>> should do the trick.
>> 
>> Second, the offset source needs to be pretty good. A 10811 tuned high with
>> both the mechanical trim and the EFC is a pretty good choice to start out.
>> 
>> If you only have one counter, simply ignore the second channel. You are now
>> running a single mixer. It still works as a comparison between the offset
>> oscillator
>> and your DUT.
>> 
>> If you want to do it properly as a DMTD, then you set up two counters. One
>> to measure mixer A and the other to measure mixer B.  Set them both up to
>> measure frequency. Time tag the data files so you know which reading
>> matches up with which.
>> 
>> Fun !!!
>> 
>> Bob
>> 
>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
>>> 
>>> Hi again Bob
>>> 
>>> I tried to do some measurements with a DMTD!
>>> In my junk box I found a little PCB from earlier experiments on that
>> topic,
>>> with a power splitter and two SRA-3H mixers, it was even already wired
>> for
>>> the DMTD configuration. So I gave it a try!
>>> As "transfer oscillator" I used my HP 8663A signal generator, and set it
>>> high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
>>> signals and at the mixer outputs, I put a little lowpass filter with
>> 100Hz
>>> corner frequency.
>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
>> tried
>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>> measure
>>> the delay between the two signals.
>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>> It does give some interesting graphs, but I don't know yet how to
>> correctly
>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
>> 

Re: [time-nuts] Phase measurement of my GPSDO

[Tobias Pluess]

Hi Bob

Riley suggests to use a single TIC

http://wriley.com/A%20Small%20DMTD%20System.pdf

when you look at the block diagram Fig. 4, you can see that one TIC allows
to compare two oscillators.
I don't know exactly how, though :-)

OK and I see your point on the 8663. I will try to use another reference!
I definitely didn't keep mine on for a long time. I didn't use the signal
generator for a while now, so it was unplugged for a few months. I assume
that's far from optimal for the 10811's stability.


Tobias



On Mon., 13 Apr. 2020, 23:53 Bob kb8tq,  wrote:

> Hi
>
> > On Apr 13, 2020, at 5:06 PM, Tobias Pluess  wrote:
> >
> > Hi Bob
> > awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >
> > Maybe I have some good OpAmps for this purpose in my box. I will try it!
> of
>
> You need something that is quiet (like the OP-37) and has a pretty good
> slew
> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
> one.
>
> > course I saw that my setup was not ideal as there was a bit of noise on
> the
> > signals which I guess does lead to some jitter in the trigger circuit and
> > therefore decreases my measurement noise floor.
>
> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
> digits.
> Net result is a measurement that’s good in the vicinity of parts in 10^-13
>
> >
> > Can you say something about how it would be done using a TIC?
> > I don't have two identically good counters, but the HP 5335A could be
> used
> > as TIC, couldn't it.
>
> The standard way of doing the test is to run two counters / two TIC/s /
> two whatever’s.
> I know of no practical way to do it with a single 5335.
>
> >
> > And the offset source I used is not directly the HP 10811, but the HP
> 8663A
> > Signal generator internally uses a 10811 as reference source. But I
> didn't
> > wait for days for it to warm up properly. (Should I?)
>
> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how
> you
> use the 10811, it needs to be on for a while. How long very much depends
> on
> just how long it’s been off. Best to keep it on all the time.
>
> >
> >> Fun !!!
> > Yea, of course! :-)
> > I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> > myself. I use TimeLab to see what numbers I should expect, and then I
> want
> > to compute it all myself in Matlab because I want to see how it actually
> > works. ;-)
>
> Be careful any time you code this stuff for the first time. It’s amazingly
> easy
> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
> you should not code it up yourself. I generally do it in Excel or in C.
>
> Bob
>
> >
> >
> > Best
> > Tobias
> >
> >
> >
> > On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> Ok, first the math:
> >>
> >> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>
> >> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>
> >> You get to add a 6 to what Time Lab shows you.
> >>
> >> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> >> gets you to 1x10^-10
> >>
> >> So, what’s going on?
> >>
> >> You can’t feed the mixer outputs straight into a counter. The counter
> >> front
> >> end does not handle LF audio sine waves very well. You need to do an
> >> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >> similar)
> >> should do the trick.
> >>
> >> Second, the offset source needs to be pretty good. A 10811 tuned high
> with
> >> both the mechanical trim and the EFC is a pretty good choice to start
> out.
> >>
> >> If you only have one counter, simply ignore the second channel. You are
> now
> >> running a single mixer. It still works as a comparison between the
> offset
> >> oscillator
> >> and your DUT.
> >>
> >> If you want to do it properly as a DMTD, then you set up two counters.
> One
> >> to measure mixer A and the other to measure mixer B.  Set them both up
> to
> >> measure frequency. Time tag the data files so you know which reading
> >> matches up with which.
> >>
> >> Fun !!!
> >>
> >> Bob
> >>
> >>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
> >>>
> >>> Hi again Bob
> >>>
> >>> I tried to do some measurements with a DMTD!
> >>> In my junk box I found a little PCB from earlier experiments on that
> >> topic,
> >>> with a power splitter and two SRA-3H mixers, it was even already wired
> >> for
> >>> the DMTD configuration. So I gave it a try!
> >>> As "transfer oscillator" I used my HP 8663A signal generator, and set
> it
> >>> high in frequency by 10 Hz. To the two mixers, I connected the two
> 10MHz
> >>> signals and at the mixer outputs, I put a little lowpass filter with
> >> 100Hz
> >>> corner frequency.
> >>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> >> tried
> >>> to feed them directly into the HP 5335A TIC and used the TI mode to
> >> measure
> >>> the delay between the two signals.
> >>> This gives 10 readings/sec, which I try 

Re: [time-nuts] Phase measurement of my GPSDO

[Bob kb8tq]

Hi

If you don’t have a spare 10811, they run about $50 to $80 on eBay. With some 
intensive shopping, 5334 or 5335 counters are in the same vicinity. Shipping on
the counters is a bit more than shipping on the 10811’s :) 

This guy:

https://www.ebay.com/itm/HP-10811-60111-10-MHz-High-Stability-Crystal-Oscillator-with-circuit-card/253425674730?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
 


Will toss in a board that has the mating connector on it. Rumor has it that 
he’ll accept
an offer for $50 if you buy 4 pieces. The “junk” rate on his parts is no worse 
than the 
typical eBay run of the mill. The up side is that 1 in 10 actually are quite 
good (for 10811’s). 

Bob

> On Apr 13, 2020, at 5:31 PM, ew via time-nuts  
> wrote:
> 
> If you have an extra 10811 use it as an offset all mine tune 20 Hz + and I 
> have used it as offset at 5 MHz , 10 Hz at 10 MHz all will do.
> Bert Kehren
> In a message dated 4/13/2020 5:07:38 PM Eastern Standard Time, 
> tplu...@ieee.org writes:
> 
> Hi Bob
> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> 
> Maybe I have some good OpAmps for this purpose in my box. I will try it! of
> course I saw that my setup was not ideal as there was a bit of noise on the
> signals which I guess does lead to some jitter in the trigger circuit and
> therefore decreases my measurement noise floor.
> 
> Can you say something about how it would be done using a TIC?
> I don't have two identically good counters, but the HP 5335A could be used
> as TIC, couldn't it.
> 
> And the offset source I used is not directly the HP 10811, but the HP 8663A
> Signal generator internally uses a 10811 as reference source. But I didn't
> wait for days for it to warm up properly. (Should I?)
> 
>> Fun !!!
> Yea, of course! :-)
> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> myself. I use TimeLab to see what numbers I should expect, and then I want
> to compute it all myself in Matlab because I want to see how it actually
> works. ;-)
> 
> 
> Best
> Tobias
> 
> 
> 
> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> Ok, first the math:
>> 
>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>> 
>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>> 
>> You get to add a 6 to what Time Lab shows you.
>> 
>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>> gets you to 1x10^-10
>> 
>> So, what’s going on?
>> 
>> You can’t feed the mixer outputs straight into a counter. The counter
>> front
>> end does not handle LF audio sine waves very well. You need to do an
>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>> similar)
>> should do the trick.
>> 
>> Second, the offset source needs to be pretty good. A 10811 tuned high with
>> both the mechanical trim and the EFC is a pretty good choice to start out.
>> 
>> If you only have one counter, simply ignore the second channel. You are now
>> running a single mixer. It still works as a comparison between the offset
>> oscillator
>> and your DUT.
>> 
>> If you want to do it properly as a DMTD, then you set up two counters. One
>> to measure mixer A and the other to measure mixer B.  Set them both up to
>> measure frequency. Time tag the data files so you know which reading
>> matches up with which.
>> 
>> Fun !!!
>> 
>> Bob
>> 
>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
>>> 
>>> Hi again Bob
>>> 
>>> I tried to do some measurements with a DMTD!
>>> In my junk box I found a little PCB from earlier experiments on that
>> topic,
>>> with a power splitter and two SRA-3H mixers, it was even already wired
>> for
>>> the DMTD configuration. So I gave it a try!
>>> As "transfer oscillator" I used my HP 8663A signal generator, and set it
>>> high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
>>> signals and at the mixer outputs, I put a little lowpass filter with
>> 100Hz
>>> corner frequency.
>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
>> tried
>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>> measure
>>> the delay between the two signals.
>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>> It does give some interesting graphs, but I don't know yet how to
>> correctly
>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
>> the
>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
>>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
>> which
>>> is indeed my target value, BUT I expect that things are not that simple.
>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but only
>>> by 9.9Hz for 

Re: [time-nuts] Phase measurement of my GPSDO

[Bob kb8tq]

Hi

> On Apr 13, 2020, at 5:06 PM, Tobias Pluess  wrote:
> 
> Hi Bob
> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> 
> Maybe I have some good OpAmps for this purpose in my box. I will try it! of

You need something that is quiet (like the OP-37) and has a pretty good slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is one. 

> course I saw that my setup was not ideal as there was a bit of noise on the
> signals which I guess does lead to some jitter in the trigger circuit and
> therefore decreases my measurement noise floor.

Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good digits. 
Net result is a measurement that’s good in the vicinity of parts in 10^-13

> 
> Can you say something about how it would be done using a TIC?
> I don't have two identically good counters, but the HP 5335A could be used
> as TIC, couldn't it.

The standard way of doing the test is to run two counters / two TIC/s / two 
whatever’s.
I know of no practical way to do it with a single 5335.

> 
> And the offset source I used is not directly the HP 10811, but the HP 8663A
> Signal generator internally uses a 10811 as reference source. But I didn't
> wait for days for it to warm up properly. (Should I?)

The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how you
use the 10811, it needs to be on for a while. How long very much depends on 
just how long it’s been off. Best to keep it on all the time. 

> 
>> Fun !!!
> Yea, of course! :-)
> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> myself. I use TimeLab to see what numbers I should expect, and then I want
> to compute it all myself in Matlab because I want to see how it actually
> works. ;-)

Be careful any time you code this stuff for the first time. It’s amazingly easy 
( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
you should not code it up yourself. I generally do it in Excel or in C. 

Bob

> 
> 
> Best
> Tobias
> 
> 
> 
> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> Ok, first the math:
>> 
>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>> 
>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>> 
>> You get to add a 6 to what Time Lab shows you.
>> 
>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>> gets you to 1x10^-10
>> 
>> So, what’s going on?
>> 
>> You can’t feed the mixer outputs straight into a counter. The counter
>> front
>> end does not handle LF audio sine waves very well. You need to do an
>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>> similar)
>> should do the trick.
>> 
>> Second, the offset source needs to be pretty good. A 10811 tuned high with
>> both the mechanical trim and the EFC is a pretty good choice to start out.
>> 
>> If you only have one counter, simply ignore the second channel. You are now
>> running a single mixer. It still works as a comparison between the offset
>> oscillator
>> and your DUT.
>> 
>> If you want to do it properly as a DMTD, then you set up two counters. One
>> to measure mixer A and the other to measure mixer B.  Set them both up to
>> measure frequency. Time tag the data files so you know which reading
>> matches up with which.
>> 
>> Fun !!!
>> 
>> Bob
>> 
>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
>>> 
>>> Hi again Bob
>>> 
>>> I tried to do some measurements with a DMTD!
>>> In my junk box I found a little PCB from earlier experiments on that
>> topic,
>>> with a power splitter and two SRA-3H mixers, it was even already wired
>> for
>>> the DMTD configuration. So I gave it a try!
>>> As "transfer oscillator" I used my HP 8663A signal generator, and set it
>>> high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
>>> signals and at the mixer outputs, I put a little lowpass filter with
>> 100Hz
>>> corner frequency.
>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
>> tried
>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>> measure
>>> the delay between the two signals.
>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>> It does give some interesting graphs, but I don't know yet how to
>> correctly
>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
>> the
>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
>>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
>> which
>>> is indeed my target value, BUT I expect that things are not that simple.
>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but only
>>> by 9.9Hz for example).
>>> Can you give some hints on that?
>>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal
>> into
>>> a power splitter and connected the two outputs to my DMTD with two
>>> 

Re: [time-nuts] Phase measurement of my GPSDO

[ew via time-nuts]

If you have an extra 10811 use it as an offset all mine tune 20 Hz + and I have 
used it as offset at 5 MHz , 10 Hz at 10 MHz all will do.
Bert Kehren
In a message dated 4/13/2020 5:07:38 PM Eastern Standard Time, tplu...@ieee.org 
writes:

Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)

Maybe I have some good OpAmps for this purpose in my box. I will try it! of
course I saw that my setup was not ideal as there was a bit of noise on the
signals which I guess does lead to some jitter in the trigger circuit and
therefore decreases my measurement noise floor.

Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be used
as TIC, couldn't it.

And the offset source I used is not directly the HP 10811, but the HP 8663A
Signal generator internally uses a 10811 as reference source. But I didn't
wait for days for it to warm up properly. (Should I?)

> Fun !!!
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I want
to compute it all myself in Matlab because I want to see how it actually
works. ;-)


Best
Tobias



On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:

> Hi
>
> Ok, first the math:
>
> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>
> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>
> You get to add a 6 to what Time Lab shows you.
>
> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> gets you to 1x10^-10
>
> So, what’s going on?
>
> You can’t feed the mixer outputs straight into a counter. The counter
> front
> end does not handle LF audio sine waves very well. You need to do an
> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> similar)
> should do the trick.
>
> Second, the offset source needs to be pretty good. A 10811 tuned high with
> both the mechanical trim and the EFC is a pretty good choice to start out.
>
> If you only have one counter, simply ignore the second channel. You are now
> running a single mixer. It still works as a comparison between the offset
> oscillator
> and your DUT.
>
> If you want to do it properly as a DMTD, then you set up two counters. One
> to measure mixer A and the other to measure mixer B.  Set them both up to
> measure frequency. Time tag the data files so you know which reading
> matches up with which.
>
> Fun !!!
>
> Bob
>
> > On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
> >
> > Hi again Bob
> >
> > I tried to do some measurements with a DMTD!
> > In my junk box I found a little PCB from earlier experiments on that
> topic,
> > with a power splitter and two SRA-3H mixers, it was even already wired
> for
> > the DMTD configuration. So I gave it a try!
> > As "transfer oscillator" I used my HP 8663A signal generator, and set it
> > high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
> > signals and at the mixer outputs, I put a little lowpass filter with
> 100Hz
> > corner frequency.
> > The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> tried
> > to feed them directly into the HP 5335A TIC and used the TI mode to
> measure
> > the delay between the two signals.
> > This gives 10 readings/sec, which I try to process with TimeLab.
> > It does give some interesting graphs, but I don't know yet how to
> correctly
> > set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
> the
> > order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
> > simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
> > this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
> which
> > is indeed my target value, BUT I expect that things are not that simple.
> > (i.e. what if I didn't set the transfer oscillator high by +10Hz but only
> > by 9.9Hz for example).
> > Can you give some hints on that?
> > Of course I also did the noise floor test (i.e. I fed the 10MHz signal
> into
> > a power splitter and connected the two outputs to my DMTD with two
> > different lenghts of cables. This gave results starting at 1e-4 going
> down
> > to 1e-7, maybe it would have gone even lower but I measured only for a
> > couple of minutes.)
> >
> > Can you give some hints on that?
> >
> > Best
> > Tobias
> > HB9FSX
> >
> >
> >
> >
> > On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
> >>
> >>> Hi
> >>>
> >>> The quick way to do this is with a single mixer. Take something like an
> >>> old
> >>> 10811 and use the coarse tune to set it high in frequency by 5 to 10
> Hz.
> >>>
> >>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
> tone.
> >>> That tone is the *difference* between the 10811 and your device under
> >>> test.
> >>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>
> >>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
> >>> shift
> >>> ( 0.1 ppm ). At 

Re: [time-nuts] Phase measurement of my GPSDO

[Tobias Pluess]

Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)

Maybe I have some good OpAmps for this purpose in my box. I will try it! of
course I saw that my setup was not ideal as there was a bit of noise on the
signals which I guess does lead to some jitter in the trigger circuit and
therefore decreases my measurement noise floor.

Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be used
as TIC, couldn't it.

And the offset source I used is not directly the HP 10811, but the HP 8663A
Signal generator internally uses a 10811 as reference source. But I didn't
wait for days for it to warm up properly. (Should I?)

> Fun !!!
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I want
to compute it all myself in Matlab because I want to see how it actually
works. ;-)


Best
Tobias



On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq  wrote:

> Hi
>
> Ok, first the math:
>
> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>
> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>
> You get to add a 6 to what Time Lab shows you.
>
> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> gets you to 1x10^-10
>
> So, what’s going on?
>
> You can’t feed the mixer outputs straight into a counter. The counter
> front
> end does not handle LF audio sine waves very well. You need to do an
> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> similar)
> should do the trick.
>
> Second, the offset source needs to be pretty good. A 10811 tuned high with
> both the mechanical trim and the EFC is a pretty good choice to start out.
>
> If you only have one counter, simply ignore the second channel. You are now
> running a single mixer. It still works as a comparison between the offset
> oscillator
> and your DUT.
>
> If you want to do it properly as a DMTD, then you set up two counters. One
> to measure mixer A and the other to measure mixer B.  Set them both up to
> measure frequency. Time tag the data files so you know which reading
> matches up with which.
>
> Fun !!!
>
> Bob
>
> > On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
> >
> > Hi again Bob
> >
> > I tried to do some measurements with a DMTD!
> > In my junk box I found a little PCB from earlier experiments on that
> topic,
> > with a power splitter and two SRA-3H mixers, it was even already wired
> for
> > the DMTD configuration. So I gave it a try!
> > As "transfer oscillator" I used my HP 8663A signal generator, and set it
> > high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
> > signals and at the mixer outputs, I put a little lowpass filter with
> 100Hz
> > corner frequency.
> > The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> tried
> > to feed them directly into the HP 5335A TIC and used the TI mode to
> measure
> > the delay between the two signals.
> > This gives 10 readings/sec, which I try to process with TimeLab.
> > It does give some interesting graphs, but I don't know yet how to
> correctly
> > set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
> the
> > order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
> > simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
> > this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
> which
> > is indeed my target value, BUT I expect that things are not that simple.
> > (i.e. what if I didn't set the transfer oscillator high by +10Hz but only
> > by 9.9Hz for example).
> > Can you give some hints on that?
> > Of course I also did the noise floor test (i.e. I fed the 10MHz signal
> into
> > a power splitter and connected the two outputs to my DMTD with two
> > different lenghts of cables. This gave results starting at 1e-4 going
> down
> > to 1e-7, maybe it would have gone even lower but I measured only for a
> > couple of minutes.)
> >
> > Can you give some hints on that?
> >
> > Best
> > Tobias
> > HB9FSX
> >
> >
> >
> >
> > On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
> >>
> >>> Hi
> >>>
> >>> The quick way to do this is with a single mixer. Take something like an
> >>> old
> >>> 10811 and use the coarse tune to set it high in frequency by 5 to 10
> Hz.
> >>>
> >>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
> tone.
> >>> That tone is the *difference* between the 10811 and your device under
> >>> test.
> >>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>
> >>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
> >>> shift
> >>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
> change
> >>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X increase
> ).
> >>>
> >>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s
> not
> >>> that
> 

Re: [time-nuts] Phase measurement of my GPSDO

[Bob kb8tq]

Hi

Ok, first the math:

If your offset oscillator is 10 Hz high at 10 MHz, you have a:

10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD

You get to add a 6 to what Time Lab shows you.

If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10

So, what’s going on? 

You can’t feed the mixer outputs straight into a counter. The counter front 
end does not handle LF audio sine waves very well. You need to do an 
op-amp based limiter. A pair of OP-37’s in each leg ( or something similar) 
should do the trick.

Second, the offset source needs to be pretty good. A 10811 tuned high with 
both the mechanical trim and the EFC is a pretty good choice to start out. 

If you only have one counter, simply ignore the second channel. You are now
running a single mixer. It still works as a comparison between the offset 
oscillator 
and your DUT.

If you want to do it properly as a DMTD, then you set up two counters. One
to measure mixer A and the other to measure mixer B.  Set them both up to 
measure frequency. Time tag the data files so you know which reading 
matches up with which. 

Fun !!!

Bob

> On Apr 13, 2020, at 3:18 PM, Tobias Pluess  wrote:
> 
> Hi again Bob
> 
> I tried to do some measurements with a DMTD!
> In my junk box I found a little PCB from earlier experiments on that topic,
> with a power splitter and two SRA-3H mixers, it was even already wired for
> the DMTD configuration. So I gave it a try!
> As "transfer oscillator" I used my HP 8663A signal generator, and set it
> high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
> signals and at the mixer outputs, I put a little lowpass filter with 100Hz
> corner frequency.
> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I tried
> to feed them directly into the HP 5335A TIC and used the TI mode to measure
> the delay between the two signals.
> This gives 10 readings/sec, which I try to process with TimeLab.
> It does give some interesting graphs, but I don't know yet how to correctly
> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in the
> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, which
> is indeed my target value, BUT I expect that things are not that simple.
> (i.e. what if I didn't set the transfer oscillator high by +10Hz but only
> by 9.9Hz for example).
> Can you give some hints on that?
> Of course I also did the noise floor test (i.e. I fed the 10MHz signal into
> a power splitter and connected the two outputs to my DMTD with two
> different lenghts of cables. This gave results starting at 1e-4 going down
> to 1e-7, maybe it would have gone even lower but I measured only for a
> couple of minutes.)
> 
> Can you give some hints on that?
> 
> Best
> Tobias
> HB9FSX
> 
> 
> 
> 
> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
>> 
>>> Hi
>>> 
>>> The quick way to do this is with a single mixer. Take something like an
>>> old
>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 Hz.
>>> 
>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio tone.
>>> That tone is the *difference* between the 10811 and your device under
>>> test.
>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>> 
>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
>>> shift
>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the change
>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X increase ).
>>> 
>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s not
>>> that
>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>> second.
>>> 
>>> The reason its not quite that simple is that the input circuit on the
>>> counter
>>> really does not handle a 10 Hz audio tone as well as it handles a 10 MHz
>>> RF signal. Instead of getting 9 digits a second, you probably will get
>>> three
>>> *good* digits a second and another 6 digits of noise.
>>> 
>>> The good news is that an op amp used as a preamp ( to get you up to maybe
>>> 32 V p-p rather than a volt or so) and another op amp or three as
>>> limiters will
>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high pass
>>> and low pass filter ( DC offsets can be a problem ….) and you have a
>>> working
>>> device that gets into the parts in 10^-13 with your 5335.
>>> 
>>> It all can be done with point to point wiring. No need for a PCB layout.
>>> Be
>>> careful that the +/- 18V supplies to the op amp *both* go on and off at
>>> the
>>> same time ….
>>> 
>>> Bob
>>> 
>> 
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[time-nuts] Austron 2110 GPIB - update

[Skip Withrow]

Hello Time-Nuts,
It was a long, painful process - but I finally got the Austron 2110
GPIB working.  I learned a lot that is not documented in the manual
that I have, so here is some information if anyone ever tries to
operate GPIB on this unit.

1. The firmware matters.  I have both version 'F' and version 'K' of
the firmware.  Version 'F' knows nothing about GPIB.  I don't know if
there are versions intermediate to the ones that I have, but version
'K' does have the GPIB interface software incorporated.

The GPIB is controlled by the SS1 key on the front panel.  This is
documented nowhere in my manual, even though my manual has several
pages on the GPIB syntax and commands, with examples.
SS1 - 1 allows each of the commands to be individually turned off or
on in Talk Only mode.
SS1 - 2 allows you to examine the configuration of the GPIB interface
(GPIB address, SRQ setting, Talk Only setting).
SS1 - 3 allows you to reset the GPIB interface.

BTW - My manual indicates that the SS0 key displays the startup
screen, in addition, it can also be used to lock out the front panel
keyboard (this is not documented in my manual).

2. The MC68488 controller chip matters.  There were two mask sets for
this part, the early mask set with 'GG' before the date code DOES NOT
WORK.  The chip that I have working has the 'P9W' before the date
code. (it took me a while to find that one)

3. There are undocumented GPIB commands that are not in my manual.
They are FMIO, FMIX, NSTA, IMDE, TRGT, TPHI, and TIME.  TIME is pretty
obvious, and I have not investigated the others yet.

If anyone has a manual with this information included I would love to
get a copy (of just the GPIB section if nothing else).

The Austron 2110 is a neat unit, it basically is a cleanup oscillator
with a 100sec time constant, my only complaint is that the DAC
resolution is only 1E10-12.  However, there is an option (which both
of mine have) for dual inputs (either 1, 5, or 10 MHz) that are
statistically combined to discipline the oscillator in the unit.

If you have one, working or not, that you want to get rid of please
contact me (off list).

Regards,
Skip Withrow

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Re: [time-nuts] Phase measurement of my GPSDO

[Tobias Pluess]

Hi again Bob

I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that topic,
with a power splitter and two SRA-3H mixers, it was even already wired for
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set it
high in frequency by 10 Hz. To the two mixers, I connected the two 10MHz
signals and at the mixer outputs, I put a little lowpass filter with 100Hz
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I tried
to feed them directly into the HP 5335A TIC and used the TI mode to measure
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to correctly
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in the
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean I
simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
this would mean that my real ADEV is in the range of 1e-11 to 1e-12, which
is indeed my target value, BUT I expect that things are not that simple.
(i.e. what if I didn't set the transfer oscillator high by +10Hz but only
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz signal into
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going down
to 1e-7, maybe it would have gone even lower but I measured only for a
couple of minutes.)

Can you give some hints on that?

Best
Tobias
HB9FSX




On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
>
>> Hi
>>
>> The quick way to do this is with a single mixer. Take something like an
>> old
>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 Hz.
>>
>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio tone.
>> That tone is the *difference* between the 10811 and your device under
>> test.
>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>
>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
>> shift
>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the change
>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X increase ).
>>
>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s not
>> that
>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>> second.
>>
>> The reason its not quite that simple is that the input circuit on the
>> counter
>> really does not handle a 10 Hz audio tone as well as it handles a 10 MHz
>> RF signal. Instead of getting 9 digits a second, you probably will get
>> three
>> *good* digits a second and another 6 digits of noise.
>>
>> The good news is that an op amp used as a preamp ( to get you up to maybe
>> 32 V p-p rather than a volt or so) and another op amp or three as
>> limiters will
>> get you up around 6 or 7 good digits. Toss in a cap or two as a high pass
>> and low pass filter ( DC offsets can be a problem ….) and you have a
>> working
>> device that gets into the parts in 10^-13 with your 5335.
>>
>> It all can be done with point to point wiring. No need for a PCB layout.
>> Be
>> careful that the +/- 18V supplies to the op amp *both* go on and off at
>> the
>> same time ….
>>
>> Bob
>>
>
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