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Re: Variation of secondary Q

To: tesla-at-pupman-dot-com
Subject: Re: Variation of secondary Q
From: "Tesla list" <tesla-at-pupman-dot-com>
Date: Tue, 19 Mar 2002 18:04:00 -0700
Resent-Date: Tue, 19 Mar 2002 18:07:05 -0700
Resent-From: tesla-at-pupman-dot-com
Resent-Message-ID: <xoTqKB.A.MOH.3C-l8-at-poodle>
Resent-Sender: tesla-request-at-pupman-dot-com
Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Looking at the power spectrum... I also note a broad peak at aroudn 310
that looks like it has a couple of sidebands (or adjacent signals) at 300
and 320.  The broad peak would be typical of an AM station, you'd see a few
kHz of sidebands for the voice/music modulation.  The adjacent peaks could
be adjacent stations (they are, after all, 10 kHz apart in that band)

That peak at 227.4 is much too narrow to be a AM broadcast station.. it
looks like a few hundred Hz wide, at most.. LF beacon?

The 227 peak is also only about 20 dB above the noise floor, in a very
narrow detection bandwidth (what's the FFT time length?) If the recording
length was 4 mSec, then the basic resolution of the measurement in the
power spectrum is on the order of 250 Hz.  If you are comparing that to
listening on an AM scanner or radio, with an audio bandwidth of, say 3 kHz,
the SNR on the radio will be a lot worse (10 kHz total bandwidth (both
sidebands) 40:1 bandwidth ratio.. )

There are quite a few 227 kHz beacons around, although none appear to be
real close..
AB	227	PUTNY	ALBANY	GEORGIA		31-27-22.132N	084-16-34.172W	NDB	MHW/LOM
7/17/1997	24	WEST GEORGIA REGIONAL	ABY
BG	227	TOTTE	BANGOR	MAINE		44-43-39.1N	068-42-46.5W	MARKER/COMLO	OM
7/17/1997		R INTL	BGR
CG	227	CASTLEGAR	CASTLEGAR	BC	CANADA	49-26-49.892N	117-34-29.940W	NDB	MZ
7/17/1997	24		
CPC	227	CAMP	WHITEVILLE	NORTH CAROLINA		34-16-18.607N	078-42-50.060W	NDB
MHW	7/17/1997	24		
DXX	227	DAWSON/MADISON	MADISON	MINNESOTA		44-59-02.864N	096-10-45.151W	NDB
MHW	7/17/1997	24		
FZ	227	EAVES	ST LOUIS	MISSOURI		38-40-37.3N	090-32-51.5W	MARKER/COMLO	OM
7/17/1997		T OF ST LOUIS	SUS
GDX	227	GOODWIN LAKE	UPPERVILLE	VIRGINIA		38-57-14.396N	077-49-51.981W	NDB
MHW	7/17/1997	24		
LA	227	WIREY	LAKELAND	FLORIDA		27-56-07.688N	082-04-33.009W	MARKER/COMLO	OM
7/17/1997		AND LINDER REGIONAL	LAL
LMM	227	LOS MOCHIS	LOS MOCHIS		MEXICO	25-49-00N	108-59-00W	NDB	HW	7/17/1997
24		
MHM	227	MINCHUMINA	MINCHUMINA	ALASKA		63-53-02.033N	152-18-59.437W	NDB	HW
7/17/1997	24		
MPR	227	MC PHERSON	MC PHERSON	KANSAS		38-20-54.030N	097-41-14.155W	NDB	MHW
7/17/1997	24		
SJY	227	SAN JACINTO	SAN JACINTO	CALIFORNIA		33-47-41.769N	116-59-57.387W
NDB	MHW	7/17/1997	24		
SLB	227	STORM LAKE	STORM LAKE	IOWA		42-36-01.731N	095-14-39.787W	NDB	MHW
7/17/1997	24		
SNL	227	SHAWNEE	SHAWNEE	OKLAHOMA		35-21-16.3N	096-56-46.9W	NDB	MHW
7/17/1997	24		
SQ	227	PNTHR	CONNERSVILLE	INDIANA		39-46-36.82N	085-07-47.58W	MARKER/COMLO
OM	7/17/1997		L FIELD	CEV
SZO	227	SEBAGO	FRYEBURG	MAINE		43-54-15.262N	070-46-56.224W	NDB	MHW
7/17/1997	24		
TAN	227	TAUNTON	TAUNTON	MASSACHUSETTS		41-52-35.365N	071-01-01.153W	NDB	MHW
7/17/1997	24		
TN	227	MONRY	MIAMI	FLORIDA		25-51-42.554N	081-00-39.650W	MARKER/COMLO	OM
7/17/1997		COLLIER TRAINING AND TRANSITION	TNT
TNZ	227	LAWRENCE COUNTY	WALNUT RIDGE	ARKANSAS		36-12-20.242N	090-55-23.431W
NDB	MHW	7/17/1997	24		
UZ	227	RALLY	ROCK HILL	SOUTH CAROLINA		34-53-24.510N	081-04-51.285W	NDB	MHW
7/17/1997	24		


Tesla list wrote:
> 
> Original poster: "Terry Fritz" ?twftesla-at-qwest-dot-net?
> 
> Hi Paul,
> 
> At 04:34 PM 3/19/2002 +0000, you wrote:
> ?Terry wrote:
> ?...
> ?? Instead of using the signal generator that only does a tiny 20
> ?? volt P-P, why not just charge the sucker up to 1000 volts and
> ?? let an IGBT short it to ground.
> ?
> ?Yes, if you want to, it will mean you can move the field pickup
> ?further away.  As you'll see below, the data you supplied in
> ?TEK00001.CSV for the single shot is more than adequate.
> 
> Hopefully I could then use the Pearson current monitor.  That would be far
> more better signal wise.
> 
> ?
> ?The carrier at 227.4 kHz +/- 75 Hz is nothing to do with the coil,
> ?have you a strong broadcast station at that frequency nearby?
> 
> My long wave radio could not pick up anything at all near this.  Maybe one
> of the neighbors was running a Tesla coil :o)
> 
> ?...
> 
> ?ringdown highlighted in green in
> ?
> ? http://www.abelian.demon.co.uk/tmp/tek00001.croptd.gif
> ?
> ?The next step is to match a synthesised waveform of the form
> ?
> ?  A * cos( 2*pi*Fres*t) * exp( -r*t)
> ?
> ?to the cleaned up signal.  We already know the complex number A
> ?from the FT, so we only have a to do a least squares match over the
> ?the exponent r, and from this, Q = pi * Fres/r.  For this sample
> ?I get roughly 219.6 +/- 2.
> 
> Neat!  That's is right near what I was getting with the old setup.  So it
> all basically works.
> 
> ?In order to get the full accuracy on Q
> ?we'll need to subject the above synthesised waveform to the same FT
> ?band limiting as the trace signal is processed through, so that
> ?they have compatible envelopes (the band limiting means the decay
> ?is no longer quite exponential).
> ?
> ?Was the single shot TEK00001.CSV a top-volts (direct probe) or an
> ?E-field pickup, a base current pickup, or a B field pickup?  Try to
> ?avoid any probes near or on the coil.
> 
> It was a very near E-field pickup.  But I think with high voltage, the
> current monitor's signal would do fine.  I could then fire the coil with
> all remote stuff and only a long terminated coax would be needed back to
> the scope.
> 
> ?
> ?? I have been looking at the "NEW!!" Tektronix TDS3GV plug in to
> ?? enable RS-232.
> 
> I was looking at this today and the programming part and it looks like the
> way to go.  WaveStar may do it by itself but just programming it in BASIC
> looks pretty easy.  I note this PowerPC based scope has a bazaar number of
> commands...  Maybe time to upgrade to the latest firmware version (a
> freebie) too...
> 
> ?
> ?Might be worth trying the soundcard capture first, as a cheap and
> ?cheerful option.  If that could be made to work (quite likely I
> ?think) then this trace analysis method could be used by many more
> ?people.  With your sig gen set to 75kHz, a diode and an RC or two
> ?should give you a noisy 10kHz ringdown waveform at the soundcard
> ?input.
> 
> None of my cheap computers have sound.  Just getting the RS-232 interface
> seems the best ways to go and adds yet another toy to my collection. :-))
> Still trying to find a reason to by the 34970a data logger ;o))  I'll try
> to do some HV testing tonight and if all looks good I'll see about getting
> the interface.  I can always sell it on ebay for more than the new price
> :o))  Interesting how the new scopes are impossible to find used...  Not
> even parts...
> 
> ?
> ?I'll tidy up the code and send it to you.  You'll have to compile
> ?and run it on the Sun - I haven't a Green-haired Turtle in Taiwan's
> ?chance of getting this to run on windoze (yuck, spit).
> 
> Cheers,
> 
>         Terry
> 
> ?--
> ?Paul Nicholson
> ?--
> ?
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