What is the difference between bandwidth and wavebands?

[Pranav Jha]

My physics book repeatedly refers to the term "waveband" while explaining the bandwidth of AM broadcasts

It states that : The bandwidth of AM broadcasts on the LW and MW wavebands is 9kHz.

However, I haven't been able to deduce the meanings of the term "bandwidth" and "wavebands" in the sentence.
How is the term "bandwidth" in this sentence difference from the bandwidth of an internet connects (say 128 Kbps)??

 

[Bill_K]

Wave band such as LW or MW refers to a large section of the radio spectrum used for a similar purpose. Bandwidth refers to the highest audio frequency that a given signal can transmit.

According to Wikipedia, LW (long wave) is defined as a carrier frequency of 148.5 kHz–283.5 kHz, while MW (medium wave) is 520 kHz–1,610 kHz. Broadcasting rights are assigned at particular carrier frequencies, 10 kHz apart in the US and 9 kHz apart elsewhere.

 

[sophiecentaur]

My physics book repeatedly refers to the term "waveband" while explaining the bandwidth of AM broadcasts

It states that : The bandwidth of AM broadcasts on the LW and MW wavebands is 9kHz.

However, I haven't been able to deduce the meanings of the term "bandwidth" and "wavebands" in the sentence.
How is the term "bandwidth" in this sentence difference from the bandwidth of an internet connects (say 128 Kbps)??

"bandwidth", in the strict sense, refers to the frequency interval which contains (most of) the energy in a signal. In the case of an RF carrier, Amplitude Modulated by a sound signal the bandwidth would be defined as space between the upper and lower frequencies which have, on average, spectral components which are half the power level of those near the carrier frequency. (You could relate this to the upper and lower -3dB points on the frequency response.) Your figure of 9Khz is the spectrum space occupied by both upper and lower sidebands of the AM signal. This means that the maximum audio frequency will be no more than 4.5kHz in this ancient and rather wasteful system.

When used to describe digital capacity, the term 'bandwidth' is not really correct - although usage has made it acceptable. The bit rate doesn't have a simple relationship with actual spectral occupancy because the coding and modulation method can make a huge difference to the Hz per baud. It depends on to the immunity to noise and interference that you want. Modern systems can squeeze an enormous number of bits per second into each Hz of frequency spectrum. Also, the way that the source signals (pictures or sound) are coded will affect the amount of 'perceived' information greatly - hence the hierarchy of coding levels which you can choose, according to the quality of sound /picture you want.

 

[Pranav Jha]

Please differentiate between "bandwidth" and "waveband"

 

[DrGreg]

"The bandwidth of AM broadcasts on the LW and MW wavebands is 9kHz."

Please differentiate between "bandwidth" and "waveband"

Each radio station broadcasts a signal that is 9 kHz wide (a bandwidth of 9 kHz), for example from 193.5 kHz to 202.5 kHz.

The LW waveband contains all long wave radio signals, from 148.5 kHz to 283.5 kHz in Europe.

The MW waveband contains all medium wave radio signals, from 526.5 kHz to 1606.5 kHz in Europe.

 

[Drakkith]

To jump on what Dr. Greg was saying, when you tune into a "station" on the radio, that signal is 9khz wide. The next station that you can tune into must be beyond that bandwidth or the signals get mixed.

A waveband is the range of all of the bandwidths which that particular waveband contains.