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

In message <293ce126-e9ef-40a2-e742-966d638cf...@rubidium.se>, Magnus Danielson writes: I can add that as of this morning, "decimate" is also used for the act of reading only every Nth email in a long thread :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org

Re: [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

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

> 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,

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

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

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

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,

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

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

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

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

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

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

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

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

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

> 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

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

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) Messa

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

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

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

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

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

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

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

Thank you all! Peter ___ 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.

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

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

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

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

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

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

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,

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

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

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

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

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

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

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