# What is the advantage of using RF frequencies to broadcast modulated data.

#### yef smith

Joined Aug 2, 2020
750
Hello, We use RF carry signal to broadcast modulated data.
What is the advantage to use such carrier frequency?
Thanks.

#### Deleted member 115935

Joined Dec 31, 1969
0
is this home work ?

#### yef smith

Joined Aug 2, 2020
750
no only for general knowledge

#### Ya’akov

Joined Jan 27, 2019
9,117
Hello, We use RF carry signal to broadcast modulated data.
What is the advantage to use such carrier frequency?
Thanks.
What do you mean, what alternative do you have in mind? Advantage over what?

#### yef smith

Joined Aug 2, 2020
750
maybe short wavelength are good to pass data?
Avdantage of not using a mixer at all.
If we modulate amplify and broadcast the data as it is.

#### Ya’akov

Joined Jan 27, 2019
9,117
maybe short wavelength are good to pass data?
Avdantage of not using a mixer at all.
If we modulate amplify and broadcast the data as it is.
"Short wavelengths" are radio frequencies, if you wanted to send the data without mixing it with an RF signal now would you propose to do it?

You may be looking at this wrong. Radio is a medium like a wire. Would you as what the advantage of using a wire to transmit data is?

What do you replace the radio signal, or the wire, with in your scenario over which either might have an advantage?

#### yef smith

Joined Aug 2, 2020
750
why cant we broadcast data modulated as it is
for example in FM:
we convert our data into frequency mudulated ,Why RF is the wire?
Why modulated data cannot propogate as it is by itself?
Thanks.

#### Ya’akov

Joined Jan 27, 2019
9,117
why cant we broadcast data modulated as it is
for example in FM:
we convert our data into frequency mudulated ,Why RF is the wire?
Why modulated data cannot propogate as it is by itself?
Thanks.
How would you propose to broadcast data using frequency modulation without a carrier signal? What will you modulate?

#### DickCappels

Joined Aug 21, 2008
10,168
The advantage over transmitting it as just the baseband signal is that you can get an efficient antenna and therefore greater range.

#### yef smith

Joined Aug 2, 2020
750
Wow you are correct,half wavelength antenna in baseband will be huge.
Thanks.

#### bertus

Joined Apr 5, 2008
22,276

#### Ya’akov

Joined Jan 27, 2019
9,117
The advantage over transmitting it as just the baseband signal is that you can get an efficient antenna and therefore greater range.
I think "efficient" might be misleading, practical seems more to the point. If would be practically impossible to use the baseband frequencies of data to generate RF signals.

I misunderstood the TS question, though. He said "we use RF", and "what is the advantage to using such carrier frequency?"

Since to actually use RF, you have to use the carrier for practical reasons, it looked like one question.

#### DickCappels

Joined Aug 21, 2008
10,168
I have transmitted encoded data made by wiggling an microcontroller output pin at 4 kbps, and my antenna, using the broadest of meanings, was a capacitive coupling of 16e-15 F with a distance of 2.5 M. You are right, at that frequency a "real" antenna was out of the question.

#### Ya’akov

Joined Jan 27, 2019
9,117
I have transmitted encoded data made by wiggling an microcontroller output pin at 4 kbps, and my antenna, using the broadest of meanings, was a capacitive coupling of 16e-15 F with a distance of 2.5 M. You are right, at that frequency a "real" antenna was out of the question.
I do love to do the improbable, things like that, or other crazy things that should work, do do when you try them. I assume that questions here, unless otherwise specified, are practical one.

At one time, any radio looked like doing what you did because we really had no idea what practical radio was and just being able to cause something at a distance was marvelous.

Language barriers can also interfere and recovering the message from the distortion can be a challenge.

#### BobTPH

Joined Jun 5, 2013
8,935
In addition to to all the other compelling reasons people have given, consider this. What if all FM radio stations did not use a carrier, but created EM waves at the frequencies of the content. How would you then tune one station and reject the others?

Bob

#### yef smith

Joined Aug 2, 2020
750
Hello BobTPH,Yes very good reason. thank you very much

#### BobaMosfet

Joined Jul 1, 2009
2,112
Hello, We use RF carry signal to broadcast modulated data.
What is the advantage to use such carrier frequency?
Thanks.
You're missing the point. A carrier frequency represents 0 in the EM signal that is the wave-from of RF energy being broadcast. Without the carrier signal, there is no reference.

#### Deleted member 115935

Joined Dec 31, 1969
0
What a great question,

I'd look at it in a few different ways

The requirement,
is to move data form one place to another.

yes there are many ways of doing that , we will assume its going to be wireless.

We could use air pressure ( i.e. sound ) , or an electro magnetic wave,
be that light, or heat , or low frequency radio , high frequency radio or X ray or what ever.

The transmission methods all have things going for them and against,
Lets concentrate of electro magnetic, which is all about wave length,

With no modulation / carrier, we are at the rate of the data.
this is easy, but the size / type of antenna needed could be huge.

With out modulation, we have data, assuming digital as 1 or 0,
if its a lot of say '1's , then that's effectively a dc output, like your car battery , wont get much range.

Modulation , allows us to play with the spectrum of the data,
We can move the spectrum to a frequency we want, to make an antenna / power source practical,
We can move the spectrum to one that does not interfere with others,
We can use modulation to make the data more robust,
e.g.. FM radio is less prone to noise than AM,
We can even use modulation to make the data look like noise, and in fact be below the ambient noise, but still receivable,
as in the signals from the voyager space craft ,

Modulation as such is just a tool to allow engineers to trade off requirements.,

#### Audioguru again

Joined Oct 21, 2019
6,688
Without radio frequencies then portable phones, portable radios, car radios and car satellite receivers cannot be used.
Many wires from each of the radio and TV stations must come to my home.

#### BobTPH

Joined Jun 5, 2013
8,935
Oh, yeah? Cant we just modulate gravitational waves?

Bob