Non educated EMF attempt.

[vlad777]

I will take 5 inch plate and connect it to
square wave oscillator with push pull output.
I figure that this plate will form capacitor with earth
and I expect to run some current trough it.

So if I get few mA how do I calculate EMF power?

It is gonna take me time to do this coz I'm slow
but will report.
I can measure frequencies up to 200kHz but
I think I will try higher.

(This is not entirely meanigless coz I think about bilding
some kind of receiver/transmitter.)

Please comment.
Many thanks.

 

[audioguru]

I little 5" plate is too small to make a capacitor unless it is extremely close to another 5" plate or extremely close to ground.
But the current at 200kHz will be so low that you probably will be unable to measure it and will be lower at lower frequencies.

The square-wave signal produces many harmonics that cause radio interference at many frequencies.

Your circuit will not transmit much because it is missing an antenna. For your very low frequencies then the antenna must be very long.

 

[vlad777]

I'll try anyway.

I been thinking about this:
Screwdriver voltage tester works even if I jump so I must conclude
that my body surface creates capacitor with earth.
This is 220V but only 50Hz, and gives few mA for that little (neon?) light.

So what happens at higher frequency ; as for voltage, come to think about it, I can go as high as 220V
or even use microwave oven step up transformer ?

I want to use square wave only because it is easy to build, and later maybe something better.

Here is a newbie question: Why do they (sometimes) call ferrite coil (in input resonant circuit) antenna ?

 

[audioguru]

I just tried my neon voltage tester.
In a very dark room, I held one terminal and waved the other terminal. No light.
Again in the dark room I held one terminal and touched the other terminal to a waterpipe ground then to an electrical ground. No Light.
Maybe you produced static electricity.

Since your neon lighted then maybe you have high voltage transmission lines over you or a high power radio station next door, or both.

Capacitance to ground has nothing to do with a neon tester picking up voltage. An antenna picks up voltage without any capacitance to ground.

A ferrite coil is half of a tuned circuit. Capacitance in parallel with a ferrite coil tunes it to a VHF frequency.
Your power transistors probably don't work as high as VHF frequencies. Maybe your ferrite coil will work at the horizontal frequency of a CRT TV.

 

[vlad777]

I just tried my neon voltage tester.
In a very dark room, I held one terminal and waved the other terminal. No light.
Again in the dark room I held one terminal and touched the other terminal to a waterpipe ground then to an electrical ground. No Light.
Maybe you produced static electricity.

Not sure what you did.
Sorry I wasn't clear. I put tester in socket, touch the other end and of course it lights up.
Now I jump and when in the air it's still on. I just tried it again.
No high voltage transmission lines near.

 

[audioguru]

Your body is big so it has a fairly high capacitance to ground even when you jump.
A capacitor is not the antenna for a transmitter or a radio.

 

[vlad777]

So what is then "inside" this "capacitor" ?
Only electric field or electro-magnetic field?

You might have noticed by now that I don't know what makes antenna antenna
in theoretical sense, aside of its it's shape. Ie what is equivalent schematics of antenna?

 

[audioguru]

A capacitor has an electric field inside and does not radiate nor receive a signal. A capacitor to ground might short a signal to ground.
An antenna radiates or receives electro-magnetic waves.

Look in Google.

 

[vlad777]

**broken link removed**

Osc gives 13-92 kHz.

I have trouble with oscillator.
For C=220pF it has min R of 15k or it don't work
and if I make cap smaller it will ask for more R
which ups the f.

(1)
What is the best way with this sch or use another
to get oscillator from 1-20 Mhz ?

I connected resonator directly to output and led lights up
at 40.1 kHZ.

How much do you guess the inductance is?
I calculate 335uH .

(2)
Is it possible to acheive radio transmission at these frequencies?

(3)
Please advise about resonator/receiver/detector cause this schematic
is only to test and I need something that I will connect to
the output directly and also can pick up radio waves.

And no, I can't measure any difference with or without plate.

 

[blueroomelectronics]

I think the 4049 tops out at 1.5MHz @ 9V