carrier freq. and pulse length

Given a electromagnetic source with a certain carrier frequency, how fast
can it be modulated (modulation type aside)? Usually, it is said that the
obtainable bandwidth, by rule of thumb, is around 10% of the carrier
frequency...Does anyone know why? the physical reason?
In ON-OFF keying, can a pulse be shorter in time than a cycle of the
carrier?

thanks
fisico32

fisico32 wrote:

> Given a electromagnetic source with a certain carrier frequency, how fast
> can it be modulated (modulation type aside)?

How fast delta function could be?

> Usually, it is said that the
> obtainable bandwidth, by rule of thumb, is around 10% of the carrier
> frequency...Does anyone know why? the physical reason?

Technical difficulties with RF amplifiers and antennae.

> In ON-OFF keying, can a pulse be shorter in time than a cycle of the
> carrier?

Yes, but what is the point?

> thanks
> fisico32

VLV

>The reason I ask is because I was wondering if there is any limitation due
to a minimum number of wave cycles that need to be in a 1 bit.....
If not, as you say, then there is no difference in how short we can make a
1 bit pulse using a carrier with higher frequency than another one....

>
>fisico32 wrote:
>
>> Given a electromagnetic source with a certain carrier frequency, how
fast
>> can it be modulated (modulation type aside)?
>
>How fast delta function could be?
>
>> Usually, it is said that the
>> obtainable bandwidth, by rule of thumb, is around 10% of the carrier
>> frequency...Does anyone know why? the physical reason?
>
>Technical difficulties with RF amplifiers and antennae.
>
>> In ON-OFF keying, can a pulse be shorter in time than a cycle of the
>> carrier?
>
>Yes, but what is the point?
>
>> thanks
>> fisico32
>
>VLV
>