On Wednesday, December 14, 2011 02:23:12 PM Peter C. Wallace did opine:
> On Wed, 14 Dec 2011, Mark Wendt wrote:
> > Date: Wed, 14 Dec 2011 12:09:55 -0500
> > From: Mark Wendt <mark.we...@nrl.navy.mil>
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] Scopes
> >
> > On 12/14/2011 11:58 AM, gene heskett wrote:
> >> On Wednesday, December 14, 2011 11:47:19 AM Mark Wendt did opine:
> >>> On 12/14/2011 11:10 AM, gene heskett wrote:
> >>>> That's great news Peter, but what does a fully stuffed 7623 weigh?
> >>>> My Hitachi, which of course is not a storage type, weighs maybe 10
> >>>> pounds, goes anywhere. Probes won't reach? Stick an upside down 5
> >>>> gallon paint bucket under it. :)
> >>>
> >>> That's why the good Lord allowed Tek to invent scope carts. And 9'
> >>> long probe leads. ;-)
> >>
> >> Scope carts are ok but we haven't used the one we have in 15 years,
> >> too big to get between the rows of racks.
> >>
> >> 9' leads? Those are transmission lines and there is no way to make
> >> them flat and high impedance w/o echos. You have to mentally
> >> subtract the echo's because they aren't terminated with the cables
> >> actual impedance. Even 30"ers can do that to you at the frequencies
> >> I play with. A 9 footer would have to have active electronics
> >> (power hungry and hot) in the hand piece to drive the low impedance
> >> cable, and probably a cable terminator hidden in the connector at
> >> the scope end of the cable. Last time I looked at active probes
> >> they weren't too far from a 4 digit asking price. Now, check ebay&
> >> expect to fix it.
> >
> > All depends on the kind of lead you're looking for. Your typical
> > passive probe isn't dealing with that kind of stuff. Not sure if this
> > would work in the situation you're talking about but here's a Tek 1.5
> > GHz active probe that's currently set at $115: #380392358070.
>
> For high speed digital stuff a home made passive 100-1 probe is trivial
> to make and has better than a GHz bandwith (5K 1/8W R into 50 Ohm
> Coax). This type of probe has much better fidelity than normal high
> impedance passive probes, and when you get above 20 MHz or so the 5K
> Ohm input impedance causes much less trouble than the passive probes
> relativly massive input capacitance.
>
That is true, and thanks for the reminder as I have actually used such a
setup, but 15 years back up the log & had forgotten it. Oldtimers? Don't
answer that. :)
>
> Peter Wallace
> Mesa Electronics
>
> (\__/)
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>
>
> ------------------------------------------------------------------------
> ------ Cloud Computing - Latest Buzzword or a Glimpse of the Future?
> This paper surveys cloud computing today: What are the benefits?
> Why are businesses embracing it? What are its payoffs and pitfalls?
> http://www.accelacomm.com/jaw/sdnl/114/51425149/
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Cheers, Gene
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------------------------------------------------------------------------------
Cloud Computing - Latest Buzzword or a Glimpse of the Future?
This paper surveys cloud computing today: What are the benefits?
Why are businesses embracing it? What are its payoffs and pitfalls?
http://www.accelacomm.com/jaw/sdnl/114/51425149/
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