Re: [TCML] Inductive and Capacitive reactance - units of measurement

```Hi Brian,

I feel your pain.  My replies are interspersed with your questions below...

--- On Sun, 3/7/10, Brian Hall <brianh4242@xxxxxxxxxxx> wrote:

> From: Brian Hall <brianh4242@xxxxxxxxxxx>
> Subject: [TCML] Inductive and Capacitive reactance - units of measurement
> To: tesla@xxxxxxxxxx
> Date: Sunday, March 7, 2010, 3:11 PM
>
>
>
> When planning/tuning a TC, to get XL = XC, inductive
> reactance = capacitive reactance in both the primary and
> secondary, I know is one of the goals, for the primary L and
> C and the secondary L and C to match
>
>
> so if:
>
>
>
> XL = 2(pi)FL
> where
>
> F=Frequency
> L=Inductance
>
>
>
> and
>
>
>
> XC = 1/(2(pi*FC))
> where
>
> F=Frequency
> C=Capacitance
>
>
> -what units of measurements are those formulas intended to
> be used with, for frequency in Hz/kHz/Mhz, inductance in
> henries/microhenries/some other henries, and farads,
> vary between parts commonly used in the primary and
> secondary portions of the circuit?

The capacitive and inductive reactance formulas are meant to be used with whole units, yielding an answer measured in Ohms.  Farads and Hertz are used for Xc, and Henries and Hertz for XL.  For example, calculating Xc for 1uF and 1Mhz: That's the reciprocal of 2(pi) x .000001F x 1,000,000Hz = 1/6.28 Ohms = .159 Ohms.  The ENG function on a TI-30 calculator makes electronics math much easier.

>
>
> For example I know that the topload is usually in pf and
> the tank cap usually in uf .... so some unit conversion will
> be required, but what?

u(micro) = 1/1,000,000  n(nano) = 1/1,000,000,000 and p(pico) = 1/1,000,000,000,000.  Conversion between units is easy.  Just move the decimal three places.  For example, .001u = 1n = 1000p

>
>
> Also I know that frequency is determined by the number of
> turns and the size of the winding, but in the tank circuit
> there is also the frequency at which the spark gap
> fires.  Which frequency is referred to, that of the
> primary coil dimensions, or bps of the sg, or some mix of
> both?

The tank circuit resonates in the radio frequency range, usually hundreds of kiloHertz.  The spark gap normally switches at 10s to 100s of breaks per second.  The two aren't really related.

>
> and once I can crunch the numbers to determine how to
> adjust the parts to make XL=XC for the primary, and the
> secondary
>
> -What unit of measurement is XL and XC reactance measured
> in, for both inductive and capacitance, and how does its
> unit conversion work for meaningful numbers in contruction
> for optimal performance?

They are measured in Ohms.  At the resonant frequency, Xc and XL cancel out, so don't worry too much about their respective values.

>
>
> And to put each tuned LC together, for tank and tower,
> should the XL of the primary = XL of the secondary, and
> likewise, XC of the primary cap = XC of the topload?

No.

>
>
>
> (btw I tried JavaTC and it seems too complicated ... the
> dimensions of the room in which it will be run are unknown
> so that kind of affects on the rest the numbers .. so i dont
> trust the numbers it gives me, nor do I understand what
> every field on that form means, and I know there has to be
> an easier way - i like the simple calculators on
> deepfriedneon.com that take it one part at a time for
> frequency, MMC and such)
>
>
>
>
> ----------------------------------
> Brian Hall
>

Brian,

I have a suggestion.  Locate a primer on basic electronics, including metric units and engineering notation.  You can find such a primer at the book store or library, or for free on-line.  If there are chapters on DC and AC principles, read them both.  A couple of hours of reading will probably clear the fog for you.  It takes me about 100 classroom hours to teach DC and AC basics, starting with the theory of electric current and ending with an introduction to LC filters.  I don't think TCML is an appropriate forum for a 100-hour lesson!  Besides, I'd bore you so badly you'd probably abandon the hobby.  You can learn what you need to know with a couple of hours of targeted reading.  E-mail me off-list if I can help.

Cheers,

Greg
http://myweb.cableone.net/grcarhunter

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