Why more Hertz doesn't automatically mean more bits per second.
It's tempting to treat "bandwidth" and "data rate" as the same thing measured in different units — after all, in casual speech "more bandwidth" usually just means "faster." In radio and communications engineering they are not the same quantity at all. Bandwidth is a frequency-domain measurement: how many Hertz of spectrum a signal occupies, or is allowed to occupy. Data rate is a completely different measurement: how many bits per second are actually delivered. A channel can have enormous bandwidth and still carry disappointing amounts of data — and a narrow channel can, under the right conditions, be pushed surprisingly hard. The relationship between the two is real, but it runs through two other quantities entirely: the channel's signal-to-noise ratio (SNR) and the spectral efficiency of the modulation scheme in use.