This is a question following my earlier post

http://www.eevblog.com/forum/beginners/a-few-question-on-jw-pulse-generator-based-on-2n3904/directly related, but I prefer to start a new thread uniquely (if possible ) devoted to the question of the

measure of the bandwith of the Rigol DS1054z with a Jim Williams pulse generator. The other post is devoted to the construction of pulse generators and I will continue to post there my various experiments on the matter.

I have read Tim answers in this first thread,

I have read

http://www.eevblog.com/forum/beginners/bandwidth-calculation-caveats!/msg807413/#msg807413and I still do not understand.

The problem is that I find a rise time r_t of 1.2 ns on the Rigol DS1054z that corresponds

to a bandwidth BW = 0.35 / r_t = 292 Mhz , way off the advertised 100 Mhz.

Tim proposed that i this is due to sin(x)/x interpolation, or vector display.

I have done it again with dots display, and I have the same results.

Suppressing sin(x)/x interpolation is more difficult, as it is only possible (as far as I understand)

with 3 or 4 channels.

In this case, the sampling rate falls to 250 Ms/s. According to

http://m.eet.com/media/1140862/19209-263113.pdfit is thus normal to have a smaller bandwidth

At this sampling rate, I found nearly the same curve, whether or not I use the

sin(x)/x interpolation.

The figure given by the Rigol measure is

4.05 ns without sin(x)/x - > 86 Mhz

and

3.75 ns with sin(x)/x -> 93 Mhz

but this is only due to the difference of maximum, not to a difference in the slope, and this

is minor compared to the huge difference at 1 Gs/s.

When I increase to 500Ms/S I get 2.8 ns - > 125 Mhz ( sin(x)/x on)

and at 1Gs/s 1.4 ns -> 250 Mhz (sin(x)/x) on).

Edit :

So my question remains : what is the real bandwidth of the Rigol DS1054z at full sample rate (1Gs/s) ?

How to relate the rise time to the band width ? All the notes I have seen are minor differences, of a few (max 20) %,

here we speak of a factor of 2-3.