Re: Science fair project results -test for viability

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

I note that at low frequencies (< 1MHz) a loop antenna may be much more
efficient, for a given small physical size, than a dipole.  Example: AM
radios using ferrite cored loop (loopstick).  This is, of course a magnetic
field antenna (as opposed to an electric field antenna, like a dipole), but
E and M fields go together.

If I were trying to extract energy from the fields created by a TC, I'd use
a multiturn loop.

As far as effiency of transmitting power goes, I'll bet that if the
secondary isn't breaking out, it makes no difference in the radiated field
whether the secondary is there or not.  Fields are radiated by changing
current.  The primary, by itself, would make a dandy transmitting antenna.
The wavelength is so long that neither primary nor secondary is even close
to a wavelength.


Now, if you are trying to create a high E field, as for the purposes of
lighting fluorescent lights, for instance, then the secondary helps by
providing a bit of impedance transformation.

> 
>   What kind of antenna was used ?
>         untuned receivers and antennas may be expected to be very
inefficient.
>           Even the signal diode switching characteristic at 200kHz merits
> consideration.
> 
>         SLAP: efficient antenna is required for efficient power transfer,
>         1/2 wave dipole antenna Length feet = 468/f_MHz = 468000/F_kHz
>         example 468000/200 = 2340 feet (This is very long)
>         What can be done to get good efficiency at a shorter length ?
>         note: the Transmitter and Receiver both need efficient antennas.
> 
>   Was the receiver a tuned circuit ?
>   What affects receiver efficiency ?
>   Was there TC break out ? Is that desirable or not & Why ?
> 
>   Was all the energy received radiated from the secondary electrostatic
> field ?
>                 Does that matter ?? Why ?
>         Could a portion of the received energy be due to direct
>         magnetic field induction coupled from the Primary
>         due to the close proximity of the receiver ?
> 
> What were your 3 measured voltages across 10K expressed as average powers ?
>  Power, a product of voltage * current in a load,
>  is the proper quantity to compare.
>   (scientific law involved: ohm's law, Efficiency = 100*Pout/Pin,
> 
>    DC detector voltage = average if there is no droop due to RC
>         (note: your diode detector is a voltage peak detector)
> 
>    convert your measured voltage and load to power (watt)
>    E=IR, I=E/R, P=IE, P=E^2/R;  P=1/t, t=1/P (waveform Period = 1/time)
>         (Prcvd-at-0.5M = 1.4^2/10000 = 0.000196 W = .195 milliwatt - 196
microwatts)
> 
>    other relevant SLAP: two fields, Electric and Magnetic displaced 90
degrees.
> 
>    Time Constant =RC sec = time to charge or discharge to 63% of applied
> voltage):
>         What is Time Constant affect on values chosen for receiver detector ?
>         Hint: If you have an oscilloscope,
>                 how does the receiver detector waveform appear ?
>         If you don't, then speculate.
>         (TC output = impulses of TBD duration 120/sec
>         (assumes break rate = 120/sec, needs verification)
>           which is once every 1/120 0.0083 sec, = 8.3 milliseconds.
>           RC = .1 e-6 volt * 10000 ohms = .001 sec = 1 millisecond
>                 (assumes DVM (10Mohm?) does not significantly lower
10,000 ohms
>                 i.e. does not introduce significant test error)
> 
> If you understand any of this you are ahead of the project,
> else some study is still appropriate to understand and explain your
> experiments.
> ....snip
> (lots more, like what Judges look for, student education of Judges, etc.
>   email me direct if you would like a copy)
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Monday, December 11, 2000 6:29 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Science fair project results
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <MaverickIce00-at-aol-dot-com>
> 
> Hi Michael, Everyone,
> 
> >My results were: 1.4 V -at- 0.5 meters, 0.335 V -at- 1
> >meter, and 0.007 V -at- 2 meters (as measured from toroid).

By the way, I wouldn't expect inverse square law that close (in terms of
wavelength) to the coil.  Inverse square law will only really apply in the
far field, at more than, say, 6 wavelengths away in free space, where the
near field effects have died off.  At any reasonable distance from a
typical TC, you're going to be in the near field.