subject:"\[time\-nuts\] Misuse of word \"decimate\" \(was Re\: Short term 10MHz source\)"


Hi,

On 2019-01-10 22:31, Tom Van Baak wrote:

I don't think case A makes sense.  You are throwing away information.  You
will get aliasing.

Hal,

Ah, but we do this all the time. Your GPSDO or your cesium standard outputs 10 
MHz. There are many cases where throwing 9,999,999 of every 10,000,000 is 
useful. The result is ... 1PPS.

Yes, this is throwing away information. But most of it is useless information. 
For example, if your Cs is ahead of GPS by 123 ns, you don't need 10 million 
measurements to tell you that. One will do. So 1PPS is useful here.


Sure, but decimation methods may be applicable to estimate a good value 
for it. It is not always needed, for sure, but this is one of the cases 
you want to do one of them and others the others.


Cheers,
Magnus


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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Tom Van Baak

> I don't think case A makes sense.  You are throwing away information.  You 
> will get aliasing.

Hal,

Ah, but we do this all the time. Your GPSDO or your cesium standard outputs 10 
MHz. There are many cases where throwing 9,999,999 of every 10,000,000 is 
useful. The result is ... 1PPS.

Yes, this is throwing away information. But most of it is useless information. 
For example, if your Cs is ahead of GPS by 123 ns, you don't need 10 million 
measurements to tell you that. One will do. So 1PPS is useful here.

And about aliasing, right, 1PPS is not immune to that. If your Cs clock 
secretly speed up by 5x for 200 milliseconds you would not see this crime in 
your 1PPS data. If you're worried about that happening, one solution is simply 
to measure at 10 PPS instead.

/tvb


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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Hal Murray



k8yumdoo...@gmail.com said:
> Case A:  you simply throw away samples, keeping only every nth sample,
> without regard for the frequency content of the original signal.

> Case B:  you first perform appropriate anti-aliasing filtering on the
> original signal, and only then throw away all but every nth sample

I don't think case A makes sense.  You are throwing away information.  You 
will get aliasing.

Case B can be more complicated than a traditional low pass anti-aliasing 
filter.  Consider a simple SDR (software defined radio).  The front end ADC 
captures a wide bandwidth, a filter selects a narrow chunk that you are 
interested in.  Decimation is appropriate.  The filter threw away the out of 
band signal that would get aliased on top of your signal if you didn't filter.


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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Hi

Separate reply because it is a very different case:

If you are doing ADEV for longer tau, you *do* indeed use case A. You simply 
throw
away 9 out of 10 samples when going from 1 second tau to 10 seconds. There are
a number of papers out there on just why this is the correct thing to do in 
this case.

Bob

> On Jan 10, 2019, at 1:24 PM, Dana Whitlow  wrote:
> 
> I'm confused...
> 
> I see two separate cases here:
> 
> Case A:  you simply throw away samples, keeping only every nth sample,
> without
> regard for the frequency content of the original signal.
> 
> Case B:  you first perform appropriate anti-aliasing filtering on the
> original signal, and
> only then throw away all but every nth sample>
> 
> Which casee are we talking about when we use the word "decimate"?   And
> then what
> is the correct terminology for the other case?   Inquiring minds really
> want to know...
> 
> Dana
> 
> 
> On Thu, Jan 10, 2019 at 11:49 AM Gerhard Hoffmann  wrote:
> 
>> 
>> Am 10.01.19 um 17:33 schrieb Bob Martin:
>>> 
>>> 
>>> Back in those same seventies, I was working for an army lab (Harry
>>> Diamond Labs) as a summer student. I saw a picture in a lab supply
>>> catalog of a (ein) stein of beer. I tore it out and taped it over a
>>> picture off Albert Einstein that a German physicist, Howard Brandt,
>>> had on the wall over his desk.  This was a bad idea. Howard was so
>>> incensed that he called the whole department together, hauled out the
>>> Websters Unabridged Dictionary, and forced me to read the definition
>>> of the word philistine in front of the group. Fortunately, there were
>>> many entries under the word and I chose "a native of Philistia" to
>>> read out loud. The moral is words can have many meanings and, more
>>> importantly, don't make fun of Einstein
>>> around German Physicists.
>>> 
>> I wonder if Howard even understood the intended pun.
>> 
>> 
>> Stein means stone, nothing else. I have seen/heard it used in the
>> 
>> sense of a "mug for beer" only by Americans. The closest
>> 
>> German word would be Steinkrug, but only if you want to
>> 
>> emphasize that the Krug is made of ceramics and not of glass.
>> 
>> 
>> Decimation apart of the Roman sense for me is  only throwing away samples,
>> 
>> and the need for filtering goes with it even without explicitly saying.
>> 
>> 
>> Cheers, Gerhard
>> 
>> 
>> 
>> 
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Hi

In the case of most typical downconversion setups, the samples are tossed out 
by the filter. If you put 1,000 samples into a CIC decimator and it is a 1000:1 
device,
only one sample comes out. I signal processing it is called a decimator none 
the less.

Bob

> On Jan 10, 2019, at 1:24 PM, Dana Whitlow  wrote:
> 
> I'm confused...
> 
> I see two separate cases here:
> 
> Case A:  you simply throw away samples, keeping only every nth sample,
> without
> regard for the frequency content of the original signal.
> 
> Case B:  you first perform appropriate anti-aliasing filtering on the
> original signal, and
> only then throw away all but every nth sample>
> 
> Which casee are we talking about when we use the word "decimate"?   And
> then what
> is the correct terminology for the other case?   Inquiring minds really
> want to know...
> 
> Dana
> 
> 
> On Thu, Jan 10, 2019 at 11:49 AM Gerhard Hoffmann  wrote:
> 
>> 
>> Am 10.01.19 um 17:33 schrieb Bob Martin:
>>> 
>>> 
>>> Back in those same seventies, I was working for an army lab (Harry
>>> Diamond Labs) as a summer student. I saw a picture in a lab supply
>>> catalog of a (ein) stein of beer. I tore it out and taped it over a
>>> picture off Albert Einstein that a German physicist, Howard Brandt,
>>> had on the wall over his desk.  This was a bad idea. Howard was so
>>> incensed that he called the whole department together, hauled out the
>>> Websters Unabridged Dictionary, and forced me to read the definition
>>> of the word philistine in front of the group. Fortunately, there were
>>> many entries under the word and I chose "a native of Philistia" to
>>> read out loud. The moral is words can have many meanings and, more
>>> importantly, don't make fun of Einstein
>>> around German Physicists.
>>> 
>> I wonder if Howard even understood the intended pun.
>> 
>> 
>> Stein means stone, nothing else. I have seen/heard it used in the
>> 
>> sense of a "mug for beer" only by Americans. The closest
>> 
>> German word would be Steinkrug, but only if you want to
>> 
>> emphasize that the Krug is made of ceramics and not of glass.
>> 
>> 
>> Decimation apart of the Roman sense for me is  only throwing away samples,
>> 
>> and the need for filtering goes with it even without explicitly saying.
>> 
>> 
>> Cheers, Gerhard
>> 
>> 
>> 
>> 
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>> 
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)


Dana,

Case B is what is typically what is intended. Exactly what manifests the 
processing varies.


Cheers,
Magnus

On 2019-01-10 19:24, Dana Whitlow wrote:

I'm confused...

I see two separate cases here:

Case A:  you simply throw away samples, keeping only every nth sample,
without
regard for the frequency content of the original signal.

Case B:  you first perform appropriate anti-aliasing filtering on the
original signal, and
  only then throw away all but every nth sample>

Which casee are we talking about when we use the word "decimate"?   And
then what
is the correct terminology for the other case?   Inquiring minds really
want to know...

Dana


On Thu, Jan 10, 2019 at 11:49 AM Gerhard Hoffmann  wrote:


Am 10.01.19 um 17:33 schrieb Bob Martin:


Back in those same seventies, I was working for an army lab (Harry
Diamond Labs) as a summer student. I saw a picture in a lab supply
catalog of a (ein) stein of beer. I tore it out and taped it over a
picture off Albert Einstein that a German physicist, Howard Brandt,
had on the wall over his desk.  This was a bad idea. Howard was so
incensed that he called the whole department together, hauled out the
Websters Unabridged Dictionary, and forced me to read the definition
of the word philistine in front of the group. Fortunately, there were
many entries under the word and I chose "a native of Philistia" to
read out loud. The moral is words can have many meanings and, more
importantly, don't make fun of Einstein
around German Physicists.


I wonder if Howard even understood the intended pun.


Stein means stone, nothing else. I have seen/heard it used in the

sense of a "mug for beer" only by Americans. The closest

German word would be Steinkrug, but only if you want to

emphasize that the Krug is made of ceramics and not of glass.


Decimation apart of the Roman sense for me is  only throwing away samples,

and the need for filtering goes with it even without explicitly saying.


Cheers, Gerhard




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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Hi

For a quick dive into the basics of what has to happen in order to get more bits
from an ADC when decimating:

http://www.ti.com.cn/cn/lit/an/snoa232/snoa232.pdf 

Is a free on the internet source. There are somewhat better (and more complete)
descriptions in various books. “Multirate Signal Processing” by Harris is one, 
“Digital
Signal Processing in Communications Systems” by Frerking (a TImeNut …) is 
another one. There are *many* others. 

While this is normally applied to voltage to digital conversion (ADC), it also 
very 
much applies to time to digital conversion as well. 

Bob

> On Jan 10, 2019, at 2:29 PM, Hal Murray  wrote:
> 
> 
> petervince1...@gmail.com said:
>> Could you please clarify then exactly what "decimate" means in this context.
> 
> Perhaps an example will help.
> 
> Consider an audio input system.  You want 0-20 kHz, so you need 40 k 
> samples/second.  You also need a sharp cutoff filter at 20 kHz.
> 
> An alternative approach is to sample at 160 k samples/second and implement 
> the 
> filter in software.  You still need an external anti-aliasing filter, but 
> this 
> one doesn't need to be sharp cutoff - just good enough to eliminate 
> everything 
> over 80 kHz.
> 
> But now you have 160 k samples/second when you only want 40.  The answer is 
> to 
> throw away 3 out of 4 samples.  That's decimation or downsampling.
> 
> You can downsample at non-integer rates by interpolating.
> 
> You can gain bits/sample with this sort of setup.  I'm not sure how to 
> explain 
> it.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Dana Whitlow

I'm confused...

I see two separate cases here:

Case A:  you simply throw away samples, keeping only every nth sample,
without
regard for the frequency content of the original signal.

Case B:  you first perform appropriate anti-aliasing filtering on the
original signal, and
 only then throw away all but every nth sample>

Which casee are we talking about when we use the word "decimate"?   And
then what
is the correct terminology for the other case?   Inquiring minds really
want to know...

Dana


On Thu, Jan 10, 2019 at 11:49 AM Gerhard Hoffmann  wrote:

>
> Am 10.01.19 um 17:33 schrieb Bob Martin:
> >
> >
> > Back in those same seventies, I was working for an army lab (Harry
> > Diamond Labs) as a summer student. I saw a picture in a lab supply
> > catalog of a (ein) stein of beer. I tore it out and taped it over a
> > picture off Albert Einstein that a German physicist, Howard Brandt,
> > had on the wall over his desk.  This was a bad idea. Howard was so
> > incensed that he called the whole department together, hauled out the
> > Websters Unabridged Dictionary, and forced me to read the definition
> > of the word philistine in front of the group. Fortunately, there were
> > many entries under the word and I chose "a native of Philistia" to
> > read out loud. The moral is words can have many meanings and, more
> > importantly, don't make fun of Einstein
> > around German Physicists.
> >
> I wonder if Howard even understood the intended pun.
>
>
> Stein means stone, nothing else. I have seen/heard it used in the
>
> sense of a "mug for beer" only by Americans. The closest
>
> German word would be Steinkrug, but only if you want to
>
> emphasize that the Krug is made of ceramics and not of glass.
>
>
> Decimation apart of the Roman sense for me is  only throwing away samples,
>
> and the need for filtering goes with it even without explicitly saying.
>
>
> Cheers, Gerhard
>
>
>
>
> ___
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Hal Murray



petervince1...@gmail.com said:
> Could you please clarify then exactly what "decimate" means in this context.

Perhaps an example will help.

Consider an audio input system.  You want 0-20 kHz, so you need 40 k 
samples/second.  You also need a sharp cutoff filter at 20 kHz.

An alternative approach is to sample at 160 k samples/second and implement the 
filter in software.  You still need an external anti-aliasing filter, but this 
one doesn't need to be sharp cutoff - just good enough to eliminate everything 
over 80 kHz.

But now you have 160 k samples/second when you only want 40.  The answer is to 
throw away 3 out of 4 samples.  That's decimation or downsampling.

You can downsample at non-integer rates by interpolating.

You can gain bits/sample with this sort of setup.  I'm not sure how to explain 
it.


-- 
These are my opinions.  I hate spam.




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[time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Mark Sims

Yes, my use of "decimate" was not a good one.   I was going to use "round", but 
the previous discussion sort of implied to me that the least significant data 
values were just going to be chopped off and not rounded.  "Truncate" would 
have been better, but the word eluded me at the time.  Since it was mentioned 
to get the data to 10 ps resolution, the word "decimate" sprang from my addled 
mind to my finger tips.

Anyway,  I am a great fan of reporting sensor data to the full 
resolution/values that the device/calculations generate and not massaging it 
further.  You never know if anything useful might be hiding in the "grass".   
Report the data as collected and let the users 
process/filter/truncate/modify/smash/bash it as they see fit.
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Tom Van Baak

> In his comment below, Mark has used the word "decimate".

I contacted Mark about this as soon as he posted yesterday. It turns out he did 
not mean decimate. It's just the word he accidentally chose. He was offering an 
opinion on precision or resolution; not decimation.

Decimation involves a reduction in the number of samples; a lowering of the 
sample rate.

The discussion is about improving TICC resolution. You might think "the more 
digits the better". If 10 is good, turn it up to 11, or 12, or maybe even 15 
(as a Bob special). But it turns out it's more complicated than that in the 
case of the TICC. More digits isn't always better. I'll explain in detail later.

Meanwhile, don't let this decimate thread go too far. It's not what Mark meant. 
Treat it more like a typo than a manifesto.

/tvb


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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Dan Kemppainen


Hi,

As I'm inclined pop my head up and throw my opinion in here...

Since the internal clock (ring oscillator) is essentially free running 
in the TDC7200 it really has a 55ps +/- xxx ps resolution. That is to 
say, it may be 55ns, or 55.001ns, or 54.999ns resolution. It's possible 
those extra digits may actually give meaningful data, so I'm inclined to 
suggest leaving the digits in there.


In any case, this discussion regarding the TICC/TDC7200 resolution and 
calibration process is probably helpful to many. I've picked up a few 
details in the last day or so.


Dan

On 1/10/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote:

Date: Thu, 10 Jan 2019 07:54:20 -0500
From: "John Ackermann.  N8UR"
To: Discussion of precise time and frequency measurement
    
Subject: Re: [time-nuts] Misuse of word "decimate" (was Re: Short term
10MHz source)
Message-ID:<29bb671d-83d4-4375-8f4c-0bad25ecb...@febo.com>
Content-Type: text/plain; charset=UTF-8

And just to clarify the subject matter -- the TICC data output contains 12 
decimal places, i.e., 1 ps precision.? The actual resolution is about 55 ps, so 
the last digit is pure noise, and the penultimate digit should really be either 
5 or 0.?

To eliminate the distraction of the noise, It's under consideration to zero the 
last decimal place, and*maybe*  to round to 50 ps.? I think the last digit is a 
no-brainer, but am more hesitant about the rounding.


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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Gerhard Hoffmann



Am 10.01.19 um 17:33 schrieb Bob Martin:



Back in those same seventies, I was working for an army lab (Harry
Diamond Labs) as a summer student. I saw a picture in a lab supply 
catalog of a (ein) stein of beer. I tore it out and taped it over a 
picture off Albert Einstein that a German physicist, Howard Brandt, 
had on the wall over his desk.  This was a bad idea. Howard was so 
incensed that he called the whole department together, hauled out the 
Websters Unabridged Dictionary, and forced me to read the definition 
of the word philistine in front of the group. Fortunately, there were 
many entries under the word and I chose "a native of Philistia" to 
read out loud. The moral is words can have many meanings and, more 
importantly, don't make fun of Einstein

around German Physicists.


I wonder if Howard even understood the intended pun.


Stein means stone, nothing else. I have seen/heard it used in the

sense of a "mug for beer" only by Americans. The closest

German word would be Steinkrug, but only if you want to

emphasize that the Krug is made of ceramics and not of glass.


Decimation apart of the Roman sense for me is  only throwing away samples,

and the need for filtering goes with it even without explicitly saying.


Cheers, Gerhard




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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Bob Martin

There is a reason dictionaries supply multiple definitions to words
and it's not surprising that some engineer or scientist chose the
most common meaning of decimate in coining the name decimation
filter. I must admit it bugs me as well when the decimate is

equated with slaughter.

The meaning of words can evolve over time.
Washington DC had (has?) a radio station called WGAY back in the
seventies. The the meaning of the word gay evolved since those call
letters were first assigned. Interestingly the station formats
evolved with the word.

http://beautifulmusicradio.blogspot.com/2013/01/wgay-and-wqmr-washingtons-quality-music.html

Back in those same seventies, I was working for an army lab (Harry
Diamond Labs) as a summer student. I saw a picture in a lab supply
catalog of a (ein) stein of beer. I tore it out and taped it over a
picture off Albert Einstein that a German physicist, Howard Brandt,
had on the wall over his desk. This was a bad idea. Howard was so
incensed that he called the whole department together, hauled out
the Websters Unabridged Dictionary, and forced me to read the
definition of the word philistine in front of the group.
Fortunately, there were many entries under the word and I chose "a
native of Philistia" to read out loud. The moral is words can have
many meanings and, more importantly, don't make fun of Einstein

around German Physicists.

Bob Martin

On 1/10/2019 6:58 AM, Tim Shoppa wrote:

This is not misuse. Everyone in signal processing knows what
decimation means in this context.

I pulled out one of my older signal processing books - Gold and
Rader, "Digital Processing Of Signals", 1969 - and Decimation is
used in several places exactly as we use it today.

I looked in some of my non-digital signal processing and older
books, like MIT Rad Lab series, and don't see the term used, but
I know that I heard old-timers using decimation used in automatic
analog signal processing especially with regard to "zooming out"
on a spectrum analyzer or pinball-style pulse-height analyzer
(often the knobs gave you only factors of ten).

Tim N3QE

On Thu, Jan 10, 2019 at 7:02 AM Peter Vince
wrote:

In his comment below, Mark has used the word "decimate". There
is much debate about what this word means (presently, and/or in
the past), but common explanations refer back to Roman times
when they apparently killed one person in ten as a punishment,
and similarly "tithes" - or taxes, where one in ten was taken.
Now OK, you can argue this until the cows come home, but the
result is that the meaning isn't crystal clear, and
particularly on a technical forum where precision is paramount,
and the entire reason we are here, I believe accuracy and
clarity of expression is also important. In this instance, I
believe "truncate" would be a better word.

:-)

Regards,

Peter Vince

On Wed, 9 Jan 2019 at 23:56, Mark Sims
wrote:

... And as far as decimating the TICC output values in
firmware... please
don't. Let the user decimate the values if they want to.
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Dana Whitlow

I was moved to check on the terms "decimate" and "downsample" to see what
their
relative meanings are, and was disappointed to see that they are virtually
the same.

Perhaps Tom would be willing to discuss this point and suggest meanings to
be used
in this group.

Dana


On Thu, Jan 10, 2019 at 6:13 AM Adrian Godwin  wrote:

> Truncate, to me at least, means to shorten : ie to remove some precision by
> rounding off lower bits.
>
> I agree that the source of the word 'decimate' is unclear, but I think,
> within the field of DSP, it has a reasonably precise definition whether or
> not that corresponds with wider usage or derivation.
>
>
>
> On Thu, Jan 10, 2019 at 12:02 PM Peter Vince 
> wrote:
>
> > In his comment below, Mark has used the word "decimate".  There is much
> > debate about what this word means (presently, and/or in the past), but
> > common explanations refer back to Roman times when they apparently killed
> > one person in ten as a punishment, and similarly "tithes" - or taxes,
> where
> > one in ten was taken.  Now OK, you can argue this until the cows come
> home,
> > but the result is that the meaning isn't crystal clear, and particularly
> on
> > a technical forum where precision is paramount, and the entire reason we
> > are here, I believe accuracy and clarity of expression is also important.
> > In this instance, I believe "truncate" would be a better word.
> >
> >   :-)
> >
> >  Regards,
> >
> >   Peter Vince
> >
> > On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
> > > ...
> > > And as far as decimating the TICC output values in firmware... please
> > don't.   Let the user decimate the values if they want to.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Thank you all!

 Peter
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)



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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Hi

Pretty much every DVM out there spits out more digits than make sense accuracy 
wise. It
certainly makes sense to note in the doc’s what the accuracy / resolution of 
the device is.
Keeping the extra digit does not cost anything in this case. It *might* come in 
useful if somebody
spent the time to work out how to phase modulate the reference to “fill in the 
gaps”. As 
Magnus has noted in the past, HP did this on real world counters once upon a 
time….

Bob

> On Jan 10, 2019, at 7:54 AM, John Ackermann. N8UR  wrote:
> 
> And just to clarify the subject matter -- the TICC data output contains 12 
> decimal places, i.e., 1 ps precision.  The actual resolution is about 55 ps, 
> so the last digit is pure noise, and the penultimate digit should really be 
> either 5 or 0.  
> 
> To eliminate the distraction of the noise, It's under consideration to zero 
> the last decimal place, and *maybe* to round to 50 ps.  I think the last 
> digit is a no-brainer, but am more hesitant about the rounding.
> 
> Coming soon to a git near you...
> 
> On Jan 10, 2019, 7:13 AM, at 7:13 AM, Adrian Godwin  
> wrote:
>> Truncate, to me at least, means to shorten : ie to remove some
>> precision by
>> rounding off lower bits.
>> 
>> I agree that the source of the word 'decimate' is unclear, but I think,
>> within the field of DSP, it has a reasonably precise definition whether
>> or
>> not that corresponds with wider usage or derivation.
>> 
>> 
>> 
>> On Thu, Jan 10, 2019 at 12:02 PM Peter Vince 
>> wrote:
>> 
>>> In his comment below, Mark has used the word "decimate".  There is
>> much
>>> debate about what this word means (presently, and/or in the past),
>> but
>>> common explanations refer back to Roman times when they apparently
>> killed
>>> one person in ten as a punishment, and similarly "tithes" - or taxes,
>> where
>>> one in ten was taken.  Now OK, you can argue this until the cows come
>> home,
>>> but the result is that the meaning isn't crystal clear, and
>> particularly on
>>> a technical forum where precision is paramount, and the entire reason
>> we
>>> are here, I believe accuracy and clarity of expression is also
>> important.
>>> In this instance, I believe "truncate" would be a better word.
>>> 
>>>   :-)
>>> 
>>> Regards,
>>> 
>>>  Peter Vince
>>> 
>>> On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
 ...
 And as far as decimating the TICC output values in firmware...
>> please
>>> don't.   Let the user decimate the values if they want to.
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe, go to
>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>>> 
>> ___
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Tim Shoppa

This is not misuse. Everyone in signal processing knows what decimation
means in this context.

I pulled out one of my older signal processing books - Gold and Rader,
"Digital Processing Of Signals", 1969 - and Decimation is used in several
places exactly as we use it today.

I looked in some of my non-digital signal processing and older books, like
MIT Rad Lab series, and don't see the term used, but I know that I heard
old-timers using decimation used in automatic analog signal processing
especially with regard to "zooming out" on a spectrum analyzer or
pinball-style pulse-height analyzer (often the knobs gave you only factors
of ten).

Tim N3QE

On Thu, Jan 10, 2019 at 7:02 AM Peter Vince 
wrote:

> In his comment below, Mark has used the word "decimate".  There is much
> debate about what this word means (presently, and/or in the past), but
> common explanations refer back to Roman times when they apparently killed
> one person in ten as a punishment, and similarly "tithes" - or taxes, where
> one in ten was taken.  Now OK, you can argue this until the cows come home,
> but the result is that the meaning isn't crystal clear, and particularly on
> a technical forum where precision is paramount, and the entire reason we
> are here, I believe accuracy and clarity of expression is also important.
> In this instance, I believe "truncate" would be a better word.
>
>   :-)
>
>  Regards,
>
>   Peter Vince
>
> On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
> > ...
> > And as far as decimating the TICC output values in firmware... please
> don't.   Let the user decimate the values if they want to.
> ___
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>
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)


Peter,

No, it's not truncation per se.

Let's say you have 100 samples. With a 10-to-1 decimation you reduce 
them into 10 samples in whatever method maintaining the core value 
(phase for instance). As you do that, you get more and more bits as 
these is combined. For larger decimation ratios (often hierarchially) 
you end up having so many bits that eventually you also truncate the 
lower parts, but that is something you would try to avoid when you can.


I hope that clarifies it for you.

I am in a meeting now, so that is why I am brief.

Cheers,
Magnus - at IFCS2019 JTPC working for Group 2

On 2019-01-10 14:12, Peter Vince wrote:

Thank you for your reply Magnus.  Could you please clarify then exactly
what "decimate" means in this context.  Is it "truncation", i.e.
eliminating or ignoring the last few digits, be they decimal or binary?
And/or is there some rounding involved?

  Peter


On Thu, 10 Jan 2019 at 13:01, Magnus Danielson  wrote:


Peter,

While the word derives back to the Roman times, today it is a technical
term for data-reduction being used in professional literature, so it's
meaning has already been established.

For instance, in modern phase-noise measurement setups the sample-rate
is around 100 MS/s, and that sample-rate of multiple ADCs with
relatively high amounts of bits is way to high to hand over to software,
so it is decimated down in steps in FPGA before handing over to
software. Decimation is the term used in that context.

Cheers,
Magnus

On 2019-01-10 13:01, Peter Vince wrote:

In his comment below, Mark has used the word "decimate".  There is much
debate about what this word means (presently, and/or in the past), but
common explanations refer back to Roman times when they apparently killed
one person in ten as a punishment, and similarly "tithes" - or taxes,

where

one in ten was taken.  Now OK, you can argue this until the cows come

home,

but the result is that the meaning isn't crystal clear, and particularly

on

a technical forum where precision is paramount, and the entire reason we
are here, I believe accuracy and clarity of expression is also important.
In this instance, I believe "truncate" would be a better word.

  :-)

   Regards,

Peter Vince

On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:

...
And as far as decimating the TICC output values in firmware... please

don't.   Let the user decimate the values if they want to.



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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread David G. McGaw

In digital filtering, decimation is a reduction of sample rate, 
truncation is a reduction of precision.  Interpolation can refer to 
either of the opposite processes.  The terms downsampling and upsampling 
can be used to avoid confusion with regards to sample rate.  I am trying 
to come up with an adequate term for improving precision.  Averaging is 
one form, but not inclusive.

David N1HAC


On 1/10/19 7:59 AM, Magnus Danielson wrote:
> Peter,
>
> While the word derives back to the Roman times, today it is a 
> technical term for data-reduction being used in professional 
> literature, so it's meaning has already been established.
>
> For instance, in modern phase-noise measurement setups the sample-rate 
> is around 100 MS/s, and that sample-rate of multiple ADCs with 
> relatively high amounts of bits is way to high to hand over to 
> software, so it is decimated down in steps in FPGA before handing over 
> to software. Decimation is the term used in that context.
>
> Cheers,
> Magnus
>
> On 2019-01-10 13:01, Peter Vince wrote:
>> In his comment below, Mark has used the word "decimate".  There is much
>> debate about what this word means (presently, and/or in the past), but
>> common explanations refer back to Roman times when they apparently 
>> killed
>> one person in ten as a punishment, and similarly "tithes" - or taxes, 
>> where
>> one in ten was taken.  Now OK, you can argue this until the cows come 
>> home,
>> but the result is that the meaning isn't crystal clear, and 
>> particularly on
>> a technical forum where precision is paramount, and the entire reason we
>> are here, I believe accuracy and clarity of expression is also 
>> important.
>> In this instance, I believe "truncate" would be a better word.
>>
>>   :-)
>>
>>   Regards,
>>
>>    Peter Vince
>>
>> On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
>>> ...
>>> And as far as decimating the TICC output values in firmware... please
>> don't.   Let the user decimate the values if they want to.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to 
>> https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.febo.com%2Fmailman%2Flistinfo%2Ftime-nuts_lists.febo.com&data=02%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C74704d9a96784bf564e908d676fbc06b%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C636827221015810655&sdata=ixTtAGjUfM%2BFSNAKiLGWm9wm%2F9EQh2%2FnPmkFp80dWNI%3D&reserved=0
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

Thank you for your reply Magnus.  Could you please clarify then exactly
what "decimate" means in this context.  Is it "truncation", i.e.
eliminating or ignoring the last few digits, be they decimal or binary?
And/or is there some rounding involved?

 Peter


On Thu, 10 Jan 2019 at 13:01, Magnus Danielson  wrote:

> Peter,
>
> While the word derives back to the Roman times, today it is a technical
> term for data-reduction being used in professional literature, so it's
> meaning has already been established.
>
> For instance, in modern phase-noise measurement setups the sample-rate
> is around 100 MS/s, and that sample-rate of multiple ADCs with
> relatively high amounts of bits is way to high to hand over to software,
> so it is decimated down in steps in FPGA before handing over to
> software. Decimation is the term used in that context.
>
> Cheers,
> Magnus
>
> On 2019-01-10 13:01, Peter Vince wrote:
> > In his comment below, Mark has used the word "decimate".  There is much
> > debate about what this word means (presently, and/or in the past), but
> > common explanations refer back to Roman times when they apparently killed
> > one person in ten as a punishment, and similarly "tithes" - or taxes,
> where
> > one in ten was taken.  Now OK, you can argue this until the cows come
> home,
> > but the result is that the meaning isn't crystal clear, and particularly
> on
> > a technical forum where precision is paramount, and the entire reason we
> > are here, I believe accuracy and clarity of expression is also important.
> > In this instance, I believe "truncate" would be a better word.
> >
> >   :-)
> >
> >   Regards,
> >
> >Peter Vince
> >
> > On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
> >> ...
> >> And as far as decimating the TICC output values in firmware... please
> > don't.   Let the user decimate the values if they want to.
>
>
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)


Peter,

While the word derives back to the Roman times, today it is a technical 
term for data-reduction being used in professional literature, so it's 
meaning has already been established.


For instance, in modern phase-noise measurement setups the sample-rate 
is around 100 MS/s, and that sample-rate of multiple ADCs with 
relatively high amounts of bits is way to high to hand over to software, 
so it is decimated down in steps in FPGA before handing over to 
software. Decimation is the term used in that context.


Cheers,
Magnus

On 2019-01-10 13:01, Peter Vince wrote:

In his comment below, Mark has used the word "decimate".  There is much
debate about what this word means (presently, and/or in the past), but
common explanations refer back to Roman times when they apparently killed
one person in ten as a punishment, and similarly "tithes" - or taxes, where
one in ten was taken.  Now OK, you can argue this until the cows come home,
but the result is that the meaning isn't crystal clear, and particularly on
a technical forum where precision is paramount, and the entire reason we
are here, I believe accuracy and clarity of expression is also important.
In this instance, I believe "truncate" would be a better word.

  :-)

  Regards,

   Peter Vince

On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:

...
And as far as decimating the TICC output values in firmware... please

don't.   Let the user decimate the values if they want to.
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread John Ackermann. N8UR

And just to clarify the subject matter -- the TICC data output contains 12 
decimal places, i.e., 1 ps precision.  The actual resolution is about 55 ps, so 
the last digit is pure noise, and the penultimate digit should really be either 
5 or 0.  

To eliminate the distraction of the noise, It's under consideration to zero the 
last decimal place, and *maybe* to round to 50 ps.  I think the last digit is a 
no-brainer, but am more hesitant about the rounding.

Coming soon to a git near you...

On Jan 10, 2019, 7:13 AM, at 7:13 AM, Adrian Godwin  wrote:
>Truncate, to me at least, means to shorten : ie to remove some
>precision by
>rounding off lower bits.
>
>I agree that the source of the word 'decimate' is unclear, but I think,
>within the field of DSP, it has a reasonably precise definition whether
>or
>not that corresponds with wider usage or derivation.
>
>
>
>On Thu, Jan 10, 2019 at 12:02 PM Peter Vince 
>wrote:
>
>> In his comment below, Mark has used the word "decimate".  There is
>much
>> debate about what this word means (presently, and/or in the past),
>but
>> common explanations refer back to Roman times when they apparently
>killed
>> one person in ten as a punishment, and similarly "tithes" - or taxes,
>where
>> one in ten was taken.  Now OK, you can argue this until the cows come
>home,
>> but the result is that the meaning isn't crystal clear, and
>particularly on
>> a technical forum where precision is paramount, and the entire reason
>we
>> are here, I believe accuracy and clarity of expression is also
>important.
>> In this instance, I believe "truncate" would be a better word.
>>
>>   :-)
>>
>>  Regards,
>>
>>   Peter Vince
>>
>> On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
>> > ...
>> > And as far as decimating the TICC output values in firmware...
>please
>> don't.   Let the user decimate the values if they want to.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

2019-01-10 Thread Adrian Godwin

Truncate, to me at least, means to shorten : ie to remove some precision by
rounding off lower bits.

I agree that the source of the word 'decimate' is unclear, but I think,
within the field of DSP, it has a reasonably precise definition whether or
not that corresponds with wider usage or derivation.



On Thu, Jan 10, 2019 at 12:02 PM Peter Vince 
wrote:

> In his comment below, Mark has used the word "decimate".  There is much
> debate about what this word means (presently, and/or in the past), but
> common explanations refer back to Roman times when they apparently killed
> one person in ten as a punishment, and similarly "tithes" - or taxes, where
> one in ten was taken.  Now OK, you can argue this until the cows come home,
> but the result is that the meaning isn't crystal clear, and particularly on
> a technical forum where precision is paramount, and the entire reason we
> are here, I believe accuracy and clarity of expression is also important.
> In this instance, I believe "truncate" would be a better word.
>
>   :-)
>
>  Regards,
>
>   Peter Vince
>
> On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
> > ...
> > And as far as decimating the TICC output values in firmware... please
> don't.   Let the user decimate the values if they want to.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
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[time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)