On Sun, 14 Nov 2010 18:22:54 -0800 (PST), "Sal M. Onella"
wrote:

It may be that a 100 MHz scope has better than a 3.5 nsec risetime,
given that it is sped'ed for response flatness to that limit and its
response actually extends beyond !00 MHz.

The simple correlation between risetime and bandwidth is roughly:
BW = 1/(3·t)

Unfortunately, peaking bandwidth can degrade risetime, and vice-versa.
O'scopes have a lot of conflicting adjustments within them. The
TEK545 had something like an 8 to 12 hour tune-up procedure for the
average bench tech (a calibration specialist could do it in 3 to 4
hours).

73's
Richard Clark, KB7QHC