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Conversion of 500MHz TDS744A to 1GHz TDS784A

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Wuerstchenhund:

--- Quote from: snoopy on September 22, 2016, 08:32:15 am ---Quite impressive for the time and still is ;)

--- End quote ---

Not really, no. Not in 2001 (the date of that brochure).

KE5FX:

--- Quote from: Wuerstchenhund on September 22, 2016, 10:35:03 am ---
--- Quote from: snoopy on September 22, 2016, 08:32:15 am ---Quite impressive for the time and still is ;)

--- End quote ---

Not really, no. Not in 2001 (the date of that brochure).

--- End quote ---

Who else was doing 200K waveforms/sec?  That was really the DPO's claim to fame.

Wuerstchenhund:

--- Quote from: KE5FX on September 22, 2016, 10:59:48 am ---
--- Quote from: Wuerstchenhund on September 22, 2016, 10:35:03 am ---
--- Quote from: snoopy on September 22, 2016, 08:32:15 am ---Quite impressive for the time and still is ;)

--- End quote ---

Not really, no. Not in 2001 (the date of that brochure).

--- End quote ---

Who else was doing 200K waveforms/sec?  That was really the DPO's claim to fame.

--- End quote ---

HP already had MegaZoom, which managed higher waveform update rates without the issues of DPO (which in those scopes only worked at 1GSa/s or less which also limits the usable BW to less than 450MHz or so, could only use up to 0.5Mpts of memory so sample rates often had to drop considerably which meant further reduction in usable BW, couldn't do measurements, and suffered from loss of signal information through ineffective min/max compression), plus MegaZoom  wasn't a separate mode, it was always on.

snoopy:

--- Quote from: Wuerstchenhund on September 22, 2016, 11:44:46 am ---
--- Quote from: KE5FX on September 22, 2016, 10:59:48 am ---
--- Quote from: Wuerstchenhund on September 22, 2016, 10:35:03 am ---
--- Quote from: snoopy on September 22, 2016, 08:32:15 am ---Quite impressive for the time and still is ;)

--- End quote ---

Not really, no. Not in 2001 (the date of that brochure).

--- End quote ---

Who else was doing 200K waveforms/sec?  That was really the DPO's claim to fame.

--- End quote ---

HP already had MegaZoom, which managed higher waveform update rates without the issues of DPO (which in those scopes only worked at 1GSa/s or less which also limits the usable BW to less than 450MHz or so, could only use up to 0.5Mpts of memory so sample rates often had to drop considerably which meant further reduction in usable BW, couldn't do measurements, and suffered from loss of signal information through ineffective min/max compression), plus MegaZoom  wasn't a separate mode, it was always on.

--- End quote ---

You could turn off DPO and the earlier A and C models never had it anyway. Also the 784A was 1995 vintage and still could do 400K wfrms/s.

http://www.axiomtest.com/documents/models/Tektronix%20TDS784A%20Data%20Sheet.pdf

Not sure what HP had at the time.

What was the model and update rate of that HP scope ?

Anyways the Tek TD694 had 3GHz bandwidth and 10Gs/s on ALL channels although it didn't have InstaVu and Fast Frame (Segmented memory) that the later 700 series had.

http://lsm.epfl.ch/files/content/sites/lsm/files/shared/Equipment/Tektronix_TDS694C.pdf

http://www.testequity.com/documents/pdf/tds684-94c.pdf



Wuerstchenhund:

--- Quote from: snoopy on September 22, 2016, 12:20:02 pm ---You could turn off DPO and the earlier A and C models never had it anyway.
--- End quote ---

You had to turn it off if you wanted to use the full BW and sample rate, and the measurements.


--- Quote ---Also the 784A was 1995 vintage and still could do 400K wfrms/s.
--- End quote ---

Yes, they had InstaVu, a non-graded persistence display. And similar to DPO, it came with the same disadvantages.


--- Quote ---Not sure what HP had at the time
--- End quote ---

At that time HP came out with it's first generation of MegaZoom in the 54600 Series of scopes.


--- Quote ---What was the model and update rate of that HP scope ?
--- End quote ---

The first one were the 54645A and the 54645D (MSO version of the 54645A).

Can't remember what the waveform rate was for the original but I believe it was somewhere in the 250k wfms/s region. The important bit however was that it was not just one large number at a specific setting (as with InstaVu/DPO), it reached high update rates in almost any setting.


--- Quote ---Anyways the Tek TD694 had 3GHz bandwidth and 10Gs/s on ALL channels although it didn't have InstaVu and Fast Frame (Segmented memory) that the later 700 series had.
--- End quote ---

And it came with a miniscule amount of sample memory (30kpts, 120kpts as "long memory" option) which meant it could only sustain the sample rate at the shortest timbease settings and with longer time bases (i.e. anything over 300ns/s with standard memory or 100ns/div with "long" memory) the sample rate dropped like a stone, limiting the usable BW to a fraction of that 3GHz bandwidth, plus it lacks any advanced measurements or math functions that other scopes had at that time.

The TDS694C is a good example what's wrong with Tek: they build a DSO that was good or even great in one aspect but lacked in pretty much everything else. Which admittedly was better than it is today, where Tek scopes lack pretty much in every aspect and excel in none. Something that is reflected in their continued dwindling market share and plummeting sales.

The key to a good scope isn't in producing some single outstanding feature (that is only good for marketing), it's in a well-balanced approach to the various different properties that define a scope. Tek understood that for analog scopes, but for DSOs they have always seemed to struggle, and still are.

Anyways, I didn't want to derail this thread into a comparison of manufacturers. My point was that the TDS784C wasn't as  impressive for a scope of that class back then in 2001 as you believe it was, and much less so in 2016.

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