I think not.

See http://www.ucolick.org/~sla/leapsecs/timescales.html

Also not that POSIX time_t suffers from the same problem.

-ch

Never mind, I think I see what's wrong... you can't integrate the dBc/Hz
values directly.  You have to turn them back into linear ratios, do the
interval sum, and then, if you want dBc coming out, take 10*log10(sum).

-- john, KE5FX

From: "John Miles" jmiles@pop.net
Subject: Re: [time-nuts] Help w/integration problem
Date: Mon, 2 Jan 2006 00:49:19 -0800
Message-ID: PKEGJHPHLLBACEOICCBJGEOCGBAA.jmiles@pop.net

You are almost there... you need to square the linears sum, which is quickly
done...

sum = 0
sum = sum + pow(10,value[1]/10)
sum = sum + pow(10,value[2]/10)
...
sum = sum + pow(10,value[n]/10)
rms = sqrt(sum)
dBc = 10 * log10(sum)

Normally you would use pow(10,value[1]/20) etc. to get the amplitudes back, but
RMS is about summing the power and that is the amplitude square as you recall.

Hmm... I'm less a math-freak this morning than usual. A good morning it is
anyway.

Cheers,
Magnus

Thanks; yes, I've got the sqrt() part already, from both my original source
who requested the feature, and the Zarlink app note.

Naturally, the two sources don't agree.  Equation 13 (and others) in the
Maxim app note at http://pdfserv.maxim-ic.com/en/an/AN3359.pdf says, in
effect:

RMS = sqrt(sum * 2)

On page 7 of the Zarlink app note, the x2 factor is left outside the radical
sign:

RMS = sqrt(sum) * 2

Unlike the question of whether to interpolate the column midpoints in dBc
space or linear spectral-density space, the position of that x2 term makes a
big difference in the final result.  Any insights into who's got THAT one
right?

-- john, KE5FX

From: "John Miles" jmiles@pop.net
Subject: Re: [time-nuts] Help w/integration problem
Date: Mon, 2 Jan 2006 01:44:33 -0800
Message-ID: PKEGJHPHLLBACEOICCBJEEOEGBAA.jmiles@pop.net

I didn't bother to look at the Zarlink app note. Until now.

Yes, the magic happends between (11) and (12). The integration is 0 to infinity
and not -infinity to infinity, since we already know it mirrors arround 0.
Mind you that these are twice the power, not twice the amplitude. The energy at
fc-f will have the same energy and be coherent to the energy at fc+f, so these
energies add up perfectly. There is a special-case when you can't argue like
this, but we can look the other way here and pick out the real reference
literature when we need to.

Looks like sloppy work to me compared to the Maxim paper, which gives
motivation to the formulas.

I hope you've got some insight on that. I could dig deeper into the issue if
you are not quite satisfied. I have better references than the two PDFs you
mentioned. The whole single-sides/double-side spectra issue is a bit confusing
and painstaking at first, I know.

Cheers,
Magnus

Sorry for top posting, but I'm shifting the original topic, and
apologies for a long semi-off topic post.

I found the original post great and respect both of you guys very much.

Tonight, (perhaps some spirits, in the holiday spirit, are influencing
me, but) I thought about this discussion in a general case.

I learned from smart people and was stimulated to know that I could hang
out with people smarter than me.

I find this conversation a great example of the best use of the
internet.  John has done much work in many realms, and has shared a good
amount of his very useful creations and experience with the rest of the
world on the internet.

Magnus, I know less about but he, seems to be one of the people I would
go to for guidance on any number of subjects.

This medium has brought these two, geographically widely separate (I
assume), people together on this conversation that will probably benefit
many with John's software.

I applaud you both for your willingness to share your knowledge and many
of the products of that knowledge.

But tonight, I'm thinking about the state of the world, in general.

This is a private, and limited mailing list, but its members seem to
reflect what I see on public newsgroups. The majority of contributions
seem to be by older people. John is young by most of these standards.

Popular folklore says that the internet is populated with young people.

So my question:
Are the younger people no longer attracted to the basic questions of
science and engineering, or am I just missing the messages from young
people for some reason?

I know this mailing list is not typical, but I don't see younger people
anywhere I go to share knowledge. Wish they were there.

On Mon, 02 Jan 2006 11:42:53 +0100 (CET), Magnus Danielson
cfmd@bredband.net wrote:

[snip first message]

From: Rex rexa@sonic.net
Subject: Re: [time-nuts] Help - Hope?
Date: Mon, 02 Jan 2006 04:53:29 -0800
Message-ID: ej5ir119a0s0j98aadricj2ds92s45hlts@4ax.com

Rex,

Thanks for the kind words.

Define younger. Do they need to be 18-20 years or do olders farts like me (i'm
34) count in as younger?

But to answer your question, younger people is still attracted and there is
still plenty of people having the right mind for these things around. They are
just dispersed alot more than they used to. There is still people that WANT
to pick up the knowledge of how to use the soldering iron, eager to learn the
magics of electronics and other sciences. They may seek this in other forums
than we oldies (well, relative oldies then) did, but in the end, they usually
get around to it. I'm not all that worried, rather the opposite, they are
starting to react. Whenever I bump into someone, I toss them in the general
right direction, trying to help them not only learning the skills, but also
learning the places where to suck up knowledge and make it a regular habbit.
It takes some time, but all of a sudden they bloome and it is a joy to see.
If you have something sensible to say, there are people there to listen.

The archives are public. This is how it is done today, kiddies search through
Google. Add some knowledge on Wikipedia and you have set the trap for them to
step into.

Cheers,
Magnus