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| True analog scopes |
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| David Hess:
--- Quote from: baldurn on December 22, 2022, 10:16:39 pm ---I just compared FFT on my new Siglent SDS2104X HD with my spectrum analyzer. It was damn impressive. But even with the cheaper entry level scope SDS1104X-E you get 1 Mpts FFT which will help the average HAM operator to verify his transmitter just fine. I also find it very useful for teaching. --- End quote --- The reason I am never impressed with DSO FFTs is that they always lack the basic functionality of a true spectrum analyzer, like a noise marker and correction for RBW. These things would be trivial to add, but for whatever reason DSO designers decline to do so. My favorite mistake is when they allow averaging with FFTs, and then proceed to average the input to the FFT instead of the output. And then we get to throwing away the phase results. A 20 year old DSO with FFT is better than most DSO FFTs today. Back then they didn't know to leave stuff out. |
| alm:
--- Quote from: baldurn on December 22, 2022, 10:16:39 pm ---Never seen an analog scope that could do bode plot. --- End quote --- Any sweep function generator with any half-way decent scope with a second channel or external trigger input can do it: For more bandwidth you could use an RF sweeper and an RF diode detector probe. --- Quote ---The new entry level DSOs from Siglent and Rigol et al are fantastic devices. You are not going to find an analog scope + something that replaces all of what the DSO also does for anything less. That would be true even if the analog scope was free which is why everyone ends up with a DSO in the end. --- End quote --- The Analog Discovery probably comes the closest, and can be bought a lot cheaper than decent entry-level DSOs during sales or on the used market. It contains a DSO, but not a very good one. It is quite nice for bode plotting and FFT due to its 14 bit resolution. I think few people will argue that a modern DSO isn't much better than most analog scopes for at least 99% of use cases. But an analog scope is still infinitely better than not having a scope, and can still do a lot of useful work. Unless you have a financial interest in selling DSOs, then obviously it's a lost sale either way. In some economies, analog scopes might be available cheaply, while entry level DSOs may not be affordable. --- Quote from: David Hess on December 22, 2022, 10:52:11 pm ---A 20 year old DSO with FFT is better than most DSO FFTs today. Back then they didn't know to leave stuff out. --- End quote --- Lecroy used to be decent with this (showing phase, math on math, etc). Have they removed it from their more recent models? |
| BillyO:
--- Quote from: David Hess on December 22, 2022, 10:52:11 pm ---.. they always lack the basic functionality of a true spectrum analyzer, like a noise marker and correction for RBW. These things would be trivial to add, but for whatever reason DSO designers decline to do so. --- End quote --- Well if they did, how would they convince you to buy their spectrum analyzer? |
| BillyO:
--- Quote from: baldurn on December 22, 2022, 10:16:39 pm ---Never seen an analog scope that could do bode plot. --- End quote --- How do you think they were done in 1976? I'd use my scope and an S-100 computer system running CP/M and wrote my own BASIC program to crunch the numbers and print the graphs. DSOs are great, but we got by just fine without them. We designed and built aircraft, spaceships, cars, particle accelerators, stereos, TVs, F1 cars, Lamborghini's, satellites, radio transceivers, X-ray machines, CT-scanners, computers, etc.. We also wrote real software in C and assembler that ran word processors, spreadsheets, and engineering applications on 8-bit computer with 65,536 bytes of memory. Today we have DSOs and people writing buggy, bloated slow as f**k code that requires a million times the processor power and memory to do essentially the same thing. We're now just learning again how to put men on the moon. Progress. Don't get me wrong, I love me DSOs - all 4 of them, but rather than wait a minute for them to boot and then spend another 2 minutes getting lost in badly written menu systems, when I have to have a look at something right now, I usually head for my old Tek 465. |
| baldurn:
--- Quote from: alm on December 22, 2022, 10:56:57 pm ---Any sweep function generator with any half-way decent scope with a second channel or external trigger input can do it: --- End quote --- I can tell you that trick is nothing like the real thing. |
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