Converting Radio Signals into Electromagnetic Waves

Wow!!! that's going to be a toughie to answer...

Fields and wave theories and propagation...

Can't wait to see the simplified answers... John.

No prob...just ask one of those creationist guys! They'll say 'cos it does'

Rf not my thing...but

I'd say...

On the antenna you have an alternating voltage put there by the transmitter.

The antenna will be designed so that this alternating voltage can induce an alternating electromagnetic field which will propagate outwards in the desired manner.

So the antenna is the key thing...

After all, modern PCs have clock frquencies that are in the radar spectrum! However they don't radiate and interfere with air traffic controll because they are not matched to an antenna.

So...The RF amplifier is matched to the antenna, the antenna matches the signal to the the outside world...or 'ether' as was once believed.

Appologies to any radio hams if this is too awful an explanation!..

OK Neanderthal answer #1...

If you were to take a single electron and wiggle it back and forth, you would create an electromagnetic field. It's the changes in space of the voltage and magnetic field that causes the "electric" and "magnetic" field to propagate.

Now, consider your antenna. A hunk of metal sticking up in the air (just to keep it simple, ug!). So you have a powerful oscillator connected to this tall piece of metal. The oscillator increases and decreases the voltage on this tall piece of metal, which creates changes in the overall electromagnetic field about you. And if someone is tuned to the same frequency in which you are sending out these changes, it will cause small changes in his tall piece of metal. If he has an amplifier on his tall piece of metal, he will be able to detect your antenna's affect on his antenna and amplify these changes and receive whatever it is you're transmitting.

Remember, the first radios communicated with static caused by a high voltage spark. Good enough for dot-dot-dash-dash.

Any questions?

Hey Verm' I gotta question,

How do I hold onto that single electon with these paws?

Jeeze it's hard enough typing!

Sorry, you have to be a cat born with dactylism.

Y'know...all that bouncing & frivolity aside, Vermin,

you are GOOOOD!

5 stars.

Mark

WOT! No stars for Del.

Tight git .

Hey Verm' gimme one of your stars...go on...pleeeeease.

Okay Del.... so far I reckon you deserve at least 3 stars for admitting you're not into rf yet you tried and succeeded in giving an answer... (of sorts).

More than I did!

John.

Del

Not being tight, although I admit to being a git. The explanation by Vermin was designed beautifully for the questioner, who didn't know squat about the subject. A light and informative introduction to wireless transmission, giving a knowledge base that could easily lead to further research possibilities; and extremely well put-together. To me, that's part of the purpose of CR4's service to engineers.

The fact that you attempted a helpful response earns you a five-star rating in my books as the kind of guy that makes this website fire so well, though. I enjoy your comments when I read them in all the blogs.

Mark

....cheers, all fair comment (I'm sure you know I was jesting the 'tight git' ,E-mail us a tenner 'eh?)

That's always the prob ..trying to guess the level of expertise of the questioner...without patronising.

As one comedy sketch about childrens TV once said...

Patronising...there's a nice word children, who can spell patronising?

I don't see where the original question was answered. The originator didn't indicate how far to take an explaination.

First, there is no conversion, per se. Transmitted electromagnetic energy is generated, propagates to the antenna (usually via a transmission line) where it remains electromagnetic and is further propagated in accordance with the particular antenna design (omin-directional or in a certain direction and distributed pattern.

In receiving, the antenna similarly captures the electromagnetic/RF energy (typically a very small energy level) it is coupled back to the receiving device, again usually via a transmission line. Still electromagnetic, only to be demodulated by the receiver for the desired mode (audio, digital, etc.).

I'm waiting to see a discussion about the difference between electromagnetic and audio! It would be interesting to see what is posted!

Hi, Bill!

re your response: "In receiving, the antenna similarly captures the electromagnetic/RF energy (typically a very small energy level) it is coupled back to the receiving device, again usually via a transmission line. Still electromagnetic, only to be demodulated by the receiver for the desired mode (audio, digital, etc.)."

Given all the above, the questionner might have assumed that the "simple" magic of transmission takes place in the transmission line, or at the very least where the translation thereof into recognizable airbourne language takes place in the "receiver". Since the question was "How does...?", the Verminster dealt with it on a basic explanation level bringing us back to various points before the technology gets involved to directly address the question.

I agree with you that there is much more, and totally fascinating, technology to be addressed in the subject area; and now that the questioner knows what's going on, perhaps he/she will follow up to see how it's accomplished. Then, maybe you'll get a whack at tremendously simplifying the process of encoding/decoding airbourne signals into electrical ones, thence into high/low frequency electromagnetic wave propagation and back again into airbourne. Meanwhile, the "how" has been adequately addressed, in my opinion, for the layman.

I'm curious, in the case of the original questioner's going ahead with a knowledge base in this, what you would recommend as the subject of blog #2 by way of explanation of the above, now that we've got past the wiggly electron bit.

Mark