Electronics and Communication Engineering - Communication Systems - Discussion

This is a case of amplitude modulation with multi-tone frequencies. Here the multi-tones are 300 Hz (0.3 KHz), 800 Hz (0.8 KHz) and 2 KHz.

Now the spectrum would consist the following bands (1000+-0.3) = 1000.3/999.7, (1000+-0.8) = 1000.8/999.2 and (1000+-2) = 1002/998.

Now from the options provided, only 1000 KHz is left out. So the correct answer is B 1000 KHz.

If there are six possible frequency such as-1000000+300=1000300,1000000+800=1000800, 1000000+2000=1002000.
Now next,1000000-300=999700,100000-800=999200,
1000000-2000=998000.
Now least value of frequency is-998khz. And greatest value of frequency is 1002khz.
Then according to question that least value of frequency which is not likely present in the o/p is -1000khz because in the range from998khz to1002kz, the 1000khz is not shown hence a/q and given options 1000khz is correct.

I think it should be 998 khz.

Because we want to find least frequency it is given by Fc-Fm.

1000-2 = 998 khz.

Least likely means with less probability.

In amplitude modulation, simple case i.e. no ssb, no dsb or vsb carrier frequency is also present in the output. So according to me 1000 Khz should also be there.

fc+fm, fc, fc-fm are frequency components then in maximum cases we find 1000 in qusetion they are not specifying the type of modulation technique.

This is an example of FM , in which higher frequency components gets attenuated (i.e, less probability of occurence).

Therefore fc-fm= -1000 (lsb higher frequency component) will be the answer as per the given option, even fc+fm= 3000 will also not occur but not in the option.

D is right answer given answer B is wrong because question is asking least frequency that is present in the output means in the frequency spectrum least frequency present is 1000-2 =998 KHz so D is right answer.

Please give explaination properly.

I also agree for 998khz as it's a least frequency in AM.

Please give the explanation in an understanding manner.