Re: Variation of secondary Q

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Paul,

At 02:33 PM 3/21/2002 +0000, you wrote:
>
>The base current waveform contains far more information about the
>coil than does the voltage signal. 
>
>See the FTs,
>
> http://www.abelian.demon.co.uk/tmp/3-19v.ft.gif
> http://www.abelian.demon.co.uk/tmp/3-19i.ft.gif
>
>Notice how the higher mode content is visible in the base current
>but not in the volts signal.  There's enough info here to extract
>the F and Q of the first 3 or 4 modes, which is very nice.

Cool!  That will be pretty easy to setup.

>
> http://www.abelian.demon.co.uk/tmp/3-19i1.ft.gif
>
>which is better still - a much flatter frequency response.
>
>> If you like one of these signal type the best, let me know.
>
>Yes, the 50 ohm terminated current signal.  Not much difference
>with/without the floating ground - not sure which bit you are
>floating there.

The termination is the "proper" way to do it and I see it does work very
well.  For grounding, I was just grounding the CT through the scope cable
or the local coil ground.  It is good that they both work the same.  The
relatively low ground currents are not going to be a problem.  the FFT
looks great!!  I saw the jitter in the waveform and checked a lot if
something was wrong and I was hoping it was something good. :-))

>
>I see that the Fres has gone up a little - circa 4%, was that due
>to the departure of the fairly close E-field pickup?  If so then
>we're definately better off without it!!

I was moving stuff and it could have been many things.  I am just playing
around and not trying to consistently control things at the moment.

>
>The mode spectrum extracted from the current signal FT can be
>compared with previous modeled results for this coil,
>
>         Now         Previous
>       Measured       Modeled     Change
>f1/4:   86.2 kHz      95.4 kHz     -9.6%
>f3/4:  312.1 kHz     334.8 kHz     -6.7% 
>f5/4:  486.3 kHz     509.1 kHz     -4.5%
>
>The pattern of changes indicates that the external capacitance has
>increased quite a bit.  The modeled results are for your toroid at
>45" above ground, I guess it's lower down now, say around 36-38"?

The torroid center line is at 43 inches.  But I have the big Bertan HV
supply pretty close and I may have been standing pretty close too so don't
read too much into those numbers yet.  the big new overhead light may also
affect things.

>
>You could well be getting a few tens of kV at the toroid in this
>mode of operation - will that be safe for long term unattended use?

The power and energy is very low.  Not much behind it really.  Even if one
were well grounded, directly touching the pulse supply would do no harm and
you may hardly feel it.  The capacitance is so low.  the HV supply will go
through a lot of resistance but it too will be very low power.  Were just
charging up like 50pF.

>Does it cause any interference that might become a problem? 

I think it will have a low duty cycle.  Maybe sleep for several minutes and
turn on for 5 seconds.  should be no problem like that.

>If you
>are OK to run like this, the HT pulsing idea is growing on me, 
>because it makes the base signal usable, and the base signal
>contains a lot of info.

It appears to be giving great signals and is robust and workable.  The
circuits can all work at all temperatures and stuff reliably.  So I'll get
to work an the real setup.  It will take awhile to get it all going but it
should be great fun :-))

Cheers,

	Terry


>--
>Paul Nicholson
>--
>