[time-nuts] Rigol DS1102E down to $400
hmurray at megapathdsl.net
Mon Jan 2 07:42:54 UTC 2012
davidwhess at gmail.com said:
> Doesn't the Rigol have delayed sweep or is it zoom only?
It has a delayed sweep. You can delay long enough so that the trigger event
is not in the buffer. After you capture a buffer, you can zoom and pan
around in it.
If the sweep is 20 ms/div or faster, the screen shows 1/3 to 1/4 of the
buffer so you can zoom out slightly (after you stop it). If the sweep is 50
ms/div or slower, the screen shows the whole buffer.
It's actually a bit more complicated than that. If the sweep speed is too
fast, the buffer bandwidth is the limit so the screen shows a much smaller
portion of the window.
There are 2 buffers: 16K and 1M. (You can pick either one.) If you are
using both channels, they each get half of the buffer and half of the buffer
bandwidth. The 16K buffer writes at 1G samples/sec. The big buffer is half
> Do any GPSDOs come with a low
> jitter 1 PPS output?
TBolt and HP Z3801A both have PPS outputs. I assume they are derived from
the OSC rather than directly from the GPS receiver so I expect they are low
jitter. Aside from reducing jitter, you have to do something like that if
the PPS is going to be useful during holdover.
I'm looking at the PPS outputs from 2 TBolts, triggering on one. I've got
the scope in persist mode. There is about 2 ns of smear on the signal it's
triggering on, only 1 ns if I turn off the other channel. I think that's
just from the sampling quirks.
The other channel has smeared over 20 ns. That's after letting it collect
for 20 minutes. There is a lot of low frequency wander rather than simple
jitter. It will probably wander father if I wait longer.
These are my opinions, not necessarily my employer's. I hate spam.
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