[time-nuts] Sputnik
Magnus Danielson
magnus at rubidium.dyndns.org
Sun Oct 7 01:26:19 EDT 2007
From: SAIDJACK at aol.com
Subject: Re: [time-nuts] Sputnik
Date: Sat, 6 Oct 2007 22:05:15 EDT
Message-ID: <cc1.1ceecd14.343998db at aol.com>
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+magnus=rubidium.dyndns.org at febo.com RETRY
>
>
> In a message dated 10/5/2007 16:28:21 Pacific Daylight Time, ka2cdk at cox.net
> writes:
>
> >OK, not really a time related post...except for the clock in the CD
> >player...which begs the question, any time nuts play with creating a
> >more precise CD player using a precision oscillator? Think it would
> >make a difference? I can see the selling point now "Our CD player is
> >Rubidium controlled!"
>
> >Tom Frank
>
>
>
> Hi Tom,
>
> a related very interesting experiment is to take the Horizontal Sync signal
> from an old Tube-type TV, and feed it to a frequency counter with GPSDO time
> base (preferrably).
>
> Got to be careful about the high voltages inside the TV though!
You can avoid hitting the coil and find it at a lower voltage if you dig around
a little.
> BTW: it's not 15374KHz, there are some significant decimal digits (I don't
> recall the formula to calculate the frequency exactly, but it was the total
> number of frame lines multiplied by 59.94Hz or so).
The field-rate is 60000/1001 Hz and frame-rate is 30000/1001 Hz exactly.
This results in 525x30000/1001 Hz as line frequency, exactly.
Toss in the tolerances allowed, naturally.
The magic number 1001 is actually 7*11*13 and 525 is actually 3*25*7 so a
reduced form becomes 3*25*30000/(11*13) or 2^4*3^2*5^6/(11*13) which still is
a horrible number.
Still, the magic number is better than the magic number 193 for DS1 which is
an actual prime number.
> Then you can test how accurate the broadcasters' 27MHz reference clock is.
This is indeed a magic number since it is 1716 (11*12*13) times the NTSC line
frequency. It is at the same time 1728 (2^6*3^3) times the PAL line frequency.
You really want to know these frequency relations.
> One would be surprised how inaccurate(!) some broadcasters are, and how much
> drift some Satellite providers have.
You are in for a supprise when it comes to the MPEG-2 TS time-stamp data
stability then. :-)
> A lot of the stability is dependent on the receiver of course, and how well
> the receiver's VCXO locks to the Broadcaster.
Natuarally.
Cheers,
Magnus
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