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Show us your square wave

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Wuerstchenhund:

--- Quote from: joeqsmith on January 31, 2015, 04:56:52 pm ---
--- Quote ---It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.
--- End quote ---

Just to be clear, when I was measuring the dead times of the two DSO's, Ethernet was not used.   I never looked at how fast I could pull data off the Agilent.   
--- End quote ---

Then I guess I misunderstood your post, for which I apologize.


--- Quote ---To be clear, the Wavemasters software and PC are out dated and slow.  What would you expect for a 13 year old PC based instrument.
--- End quote ---

It doesn't have to be. If it's an 'A' model then the CPU can be upgraded to a P4 with 800MHz FSB and 1MB cache, and especially the cache helps as this is where X-Stream does all its calculations.

The software doesn't have to be old as well. On your videos I noticed that it still says "LeCroy" in the lower left corner which suggests that you're running a very old firmware. The WM8kA is still supported, and the latest software update came out just a couple of months ago, and will upgrade your scope to the same version that runs on the latest LeCroy scopes (although it won't also give you all new features of course).


--- Quote ---Using a faster Ethernet card on the PCI bus will improve download performance.
--- End quote ---

Probably, but again it might still lead to side effects. If you didn't see any then good for you, but my point was that this doesn't mean there are none or that any such upgrades will be trouble-free (which often won't be).


--- Quote ---The high end LeCroys do have some very impressive features when it comes to processing the data.   Even my old 7200 with its 68000 VME chassis has far more features than most low end modern DSOs.   Using these dated high end DSOs for home hobbies has been a blast.   LeCroy does not seem to hold a lot of resale value and as they age, like the old Wavemaster, the prices drop.   
--- End quote ---

That's true, although very high bandwidth scopes with 50ohms only inputs like the WaveMaster are generally cheaper as most people want 1M inputs and BNC. But I guess the main reason for used LeCroy scopes often being so cheap is that when thinking 'scope' most people think 'Tek' and 'Agilent', and for home users maybe 'Rigol' and 'Siglent' as well, but that's about it. LeCroy seems to be mostly overlooked on the second hand market, which is good as like you say it keeps prices low. And they did and still make some of the most advanced scopes on the market.

Rupunzell:
BNC connectors do not work well above 3 Ghz, they will be pressed to achieve a return loss of better than 20db (their mechanical dimensions and stability is a significant part of this problem). Only the very best BNC connectors work to 4-5 Ghz and they might achieve 26db return loss.

To believe any BNC connector is rated and will function to 18Ghz is pure folly.

Cheap BNC connectors will be pressed to operate even to 1 Ghz.

If manufactures of this Ghz stuff is honest about Ghz performance, BNC connectors will not be used at all.


Beyond this, there is the common 50 ohm BNC connector and less common 75 ohm BNC connector which is somewhat compatible with the 50 ohm variety, but some 75 ohm BNC connectors are NOT compatible with 50 ohm BNC connectors.


Bernice




--- Quote from: Wuerstchenhund on January 31, 2015, 12:43:39 pm ---
As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.


--- End quote ---

Wuerstchenhund:

--- Quote from: Rupunzell on January 31, 2015, 05:57:40 pm ---BNC connectors do not work well above 3 Ghz, they will be pressed to achieve a return loss of better than 20db (their mechanical dimensions and stability is a significant part of this problem). Only the very best BNC connectors work to 4-5 Ghz and they might achieve 26db return loss.
--- End quote ---

Some modern higher bandwidth scopes use connectors that look like BNC (and are mechanically compatible) but aren't and work pretty well up to 10GHz. For example, the new Keysight MSO-S has such connectors, and this scope is rated to 8GHz.

I have some adapters that use similar connectors, and some are rated to 18GHz, although the loss above say 10GHz gets pretty high.


--- Quote ---To believe any BNC connector is rated and will function to 18Ghz is pure folly.

--- End quote ---

No-one said anything about BNC being suitable to 18GHz.

Rupunzell:
For those who want a DSO, get a LeCroy.

If 1 meg is needed at the probe tip, use an active probe with the 50 ohm input and accept the limitations of 1 meg ohm with X pF at the probe tip. Ghz instrumentation are 50 ohm input are a must if one is to be honest about dealing with the realities of Ghz capability.


Bernice


--- Quote from: Wuerstchenhund on January 31, 2015, 05:23:03 pm ---
That's true, although very high bandwidth scopes with 50ohms only inputs like the WaveMaster are generally cheaper as most people want 1M inputs and BNC. But I guess the main reason for used LeCroy scopes often being so cheap is that when thinking 'scope' most people think 'Tek' and 'Agilent', and for home users maybe 'Rigol' and 'Siglent' as well, but that's about it. LeCroy seems to be mostly overlooked on the second hand market, which is good as like you say it keeps prices low. And they did and still make some of the most advanced scopes on the market.

--- End quote ---

Rupunzell:
Any BNC at 10 Ghz, not gonna work. Any manufacture that rates their BNC to 18 Ghz is being extremely dis-honest and deceptive.


Bernice



--- Quote from: Wuerstchenhund on January 31, 2015, 06:04:33 pm ---
I have some adapters that use similar connectors, and some are rated to 18GHz, although the loss above say 10GHz gets pretty high.

No-one said anything about BNC being suitable to 18GHz.

--- End quote ---


--- Quote from: Wuerstchenhund on January 31, 2015, 12:43:39 pm ---
As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.


--- End quote ---

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