Modulating index and carrier question

[comsians]

Why carrier frequency (fc) is atleast 10times higher than baseband frequency

Secondly
how to find the modulating index of the FM wave by seeing the spectrum

reply soon

thanx

 

[brmadhukar]

If the carrier frequency is higher than the modulated components shall be close to the carrier and as such filtering shall be easier.

FM: You can know if the modulation index is high or low by the variations. But not much.

Hope this helps.

B R
Madhukar

 

[the_jackal]

The carrier freq. being atleast 10times higher than baseband frequency is for FM signals only. So my question is why this specific number 10?

 

[sip]

Dear Sir,
One of the main reason for going to modulation is to reduce the antenna size. If the carrier frequency is atleast 10times greater then the baseband then we can effectively reduce the length of the antenna opproximately 10times.
Also in doing so we can effectively use the frequency multiplexing technique

 

[virgorabbit]

It is very hard to make an high gain antenna or RF amplifer of wide bandwidth, so the carrier freq must higher enough to reduce the relative bandwidth.

 

[suvendu]

i>to reduce the size of antenna
2>easy multiplexing
3>effective radiation
yaa,u can find out the β(modulation index ) by seeing the power spectrum
refer the text "communication system by proakis and salehi

 

[joinfaisal]

Dear Sir,
One of the main reason for going to modulation is to reduce the antenna size. If the carrier frequency is atleast 10times greater then the baseband then we can effectively reduce the length of the antenna opproximately 10times.
Also in doing so we can effectively use the frequency multiplexing technique

OK then why 10...why not make 20 times higher hence reduce antenna size more......or if 20 times is very high bandwidth then why not 12 or 13......I think its probably kind of standered adopted while considering antenna size..bandwidth requirment etc and everything and the optimized solution cameout would have been 10......but I dont know the exact answer truely speaking....