A ucontroller story from another forum - Your opinion

[JimB]

what i'm not sure i know well it's the difference concerning harmonics from a sinusoidal and square.

A harmonic, is a harmonic, is a harmonic.
Simply some integer multiple of the fundamental frequency.

A pure sine wave, by definition, has no harmonics.

Harmonics are distortion. If the sine wave is distorted in any way, harmonics are created.
If we feed a sinewave through a non-linear circuit, there will be distortion and harmonics will be created.
An extreme example would be putting a sinewave through a diode clipping circuit to create a square wave.
Sinewave - no harmonics
Square wave - odd order harmonics to infinity.

Have a look here:

Manual Calculation of filter

Interesting, thank you. That is more or less what I was expecting, the two pi sections make a lowpass filter. I am surprised at the amount of ripple in the passband, it looks bad, but as this is a linear scale a quick calculation shows that it is about 3dB, which is a bit more than I would...

www.electro-tech-online.com

It is part of a long convoluted discussion about filters, but it shows a grotty square wave being cleaned up into a respectable sine wave.

earlier about the 27mW calculation you said the exact number also depends on the wire impedance right?

this results from the length the diameter and the frequency and that's why it's hard to make
a precise calculation?

Think of an antenna as a kind of transformer or transducer which converts electrical energy into electro-magnetic waves and couples those waves into free space.
Free space has and impedance, 377 Ohms.
As a result of radiating the electro-magnetic wave, the antenna has an impedance at its terminals.
The value of that impedance depends on the physical form of the antenna.
At the resonant frequency of the antenna, the antenna feed impedance is pure resistance.
At frequencies below resonance the antenna feed impedance has resistance and capacitance,
and at frequencies above resonance the antenna feed impedance has resistance and inductance.

To work correctly there are two parts to an antenna, a dipole for example has two "legs".
A correctly built single monopole antenna has a second part in the form of a ground plane.
A single random wire connected to some output of a small circuit board, has a badly defined ground plane and the feed impedance will be badly defined. It will work, but maybe not very well.

JimB

 

[whiz115]

you explain very nicely.

 

[whiz115]

hi

i want to make an important update

a member gave me a clue that maybe the cause of their abrupt behavior might be a worry
as to whom they are speaking to and giving technical advices.

i don't know if i got well his reply he was saying some weird stuff i couldn't understand
about middle east fighters referencing also assad etc,

either they are crazy or they got some short of a bad experience and
they want to avoid giving electronics advices to people who might misuse them.

some of them they are even members on another uC forum i met them there afterwards
when i've made a new topic and one of them popped in and posted the link from the
previous forum as if he wanted to say:

"this guy already asks they same questions in our forums"

i don't think such forums fits me and it's sad if some online communities and up that
suspicious and unfriendly.


what's your opinion on this? it possible such a scenario?


P.S audioguru join the company say a word!