Re: 150Khz Antenna question

Tom Bruhns wrote:
> 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
produce
>> 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
>> Président Directeur Général / Chief Executive Officer
>> MULTI-ÉLECTRONIQUE (MTE) INC.www.multi-electronique.com
>> Tél. : (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. ...


Sure looks like it.


>  ... 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).
> 

Back at the university I always wondered about that: Immature fields 
(near field), juvenile fields, adolescent fields? So where does an EM 
field reach puberty?

:-)

-- 
SCNR, Joerg

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