Again, thanks Dieter for pointing out the blunders.
With respect to the BW. The spacing of the zeros of a sinc(t) closest to T0 gives the BW which is 2/T. If you pick the 2nd zeros crossing, then the BW is 1/T. Out of habit I picked the 2nd zero crossings, but then explained it incorrectly. So I've gone back and fixed that. The waveform between the 2nd zeros is very similar to what is referred to as a Ricker wavelet in reflection seismology for which the BW is approximately 1/T.
The 11810 is a sampling scope. It samples the input at 100 KSa/s. Each sample is taken at j*dT after the trigger input. They are not able to trigger on the input. To do so would require a 50 ns delay line. That would present so much capacitance that it would be impossible to get the fast rise time.
It's not like a DSO. They are peculiar beasts designed to give very fine time resolution. The minimum interval, dT, using 5120 samples per sweep is 200 fs (yes, 0.2 ps). There is no internal termination. The input circuit is a 50 ohm hybrid module. Hence the 3 V damage level.
The thru is sitting in a 50 ohm line. So the reflection shown in 149 consists of a BNC-F cable connector, the 50 ohm thru and the BNC-M cable connector in series. As shown in 142 and 145, there are multiple reflections caused by the tee. So the response of reflection response of the thru shown in 149 has been convolved with the reflection response of the tee to first order. In fact, it's convolved with the reflections from all the interfaces which precede it. That is infinitely long, though the amplitude dies off pretty quickly.
In seismic work if one needs to properly handle the reflections that follow the first one, one uses the Z transform and evaluates the expression for the poles and zeros of the transfer function. That is complex enough to merit publication as a professional paper by a prominent seismologist while I was in grad school. As it happened, I had solved the same problem as a course exercise which I turned in shorty before the paper appeared.
The bottom line is, that as Dieter pointed out, until you get well above 1 GHz, a 50 ohm thru terminator on a scope which only has a 1 M ohm input will provide accurate results. But you do need the 50 ohm thru to get accurate results if the source impedance is 50 ohms. Without it, the cable to scope interface is almost a perfect reflector. So there will be a series of reflections without it. What effect they have depends upon the timing of their arrival.
I did all the work in the previous post for my own benefit. I've been using the 11801 to evaluate connectors, cables and terminators. In the process I discovered a bug in the 11801 FW that leads to spurious events until the scope is reset. I came *very* close to posting an elaborate interpretation of what proved to be FW glitches in the response. Very plausible, but utterly wrong.
Have Fun!
Reg