Re: 150Khz Antenna question

On Jul 2, 7:29 am, "Jacques St-Pierre" <multe...@[EMAIL PROTECTED]
>
wrote:
> Anyone can help me with the design of a compact 150Khz antenna?
>
> Let me explain the goal, I need a way to induce a 150Khz signal to a
> compound for an experiment.
>
> I will build a supply using a LM555 at 13.8Vdc and a transformer to
produc=
e
> a 150Khz square wave of 140Vp-p approx.
>
> I need to couple that 150Khz signal to a sort of compact antenna to
> emit/induce the wave to the compound. The coil should be compact enough
to=

> be insert in a plastic case of 2" x 4" inches.
>
> What is the best length of wire to use? What is the best way to wound
it?
>
> Any suggestions?
>
> Jacques
>
> --
> Jacques St-Pierre
> Pr=E9sident Directeur G=E9n=E9ral / Chief Executive Officer
> MULTI-=C9LECTRONIQUE (MTE) INC.www.multi-electronique.com
> T=E9l. : (418) 724-5835

Please understand that what you are describing is not what's generally
understood as an antenna.  Antennas couple electromagnetic waves
between their environment and electronics circuits.  What you want is
either a coil to couple a 150kHz magnetic field into your sample, or
(effectively) a capacitor to couple a 150kHz electric field into your
sample.  It would also be possible to couple some of each, and since
you will presumably be very much in the near-field of your
transducers, you can adjust the ratio to suit your needs (presuming
you understand what your needs really are).  Electromagnetic waves are
generally considered as fully developed only some distance from the
transmitting antenna structure (the "far field," generally more than a
wavelength from the antenna).

The transducer you need depends on what magnetic and/or electric field
strengths you need in your sample, what the sample comprises (e.g.,
its permittivity, loss tangent and permeability and how big it is, how
uniform you need the field to be, and perhaps some other factors.)
I'd say it's way too early to be worried about the voltage out of your
excitation circuit.  Also, does the excitation really need to be
square-wave, or can it be sinusoidal?  It's far more difficult to get
square wave AC magnetic or electric fields than it is to get
sinusoidal fields.

Cheers,
Tom