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| Bode plot up to a few 100 MHz |
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| Martinn:
--- Quote from: tautech on October 04, 2023, 07:20:47 am ---As Mike pointed to earlier SDG6000X and entry into this range is 200 MHz model but can be coaxed to 500 MHz. --- End quote --- Would you have a pointer where to start looking for the "upgrade"? I scanned a few posts, so far unsuccessful |O |
| tautech:
--- Quote from: Martinn on October 04, 2023, 08:11:52 am --- --- Quote from: tautech on October 04, 2023, 07:20:47 am ---As Mike pointed to earlier SDG6000X and entry into this range is 200 MHz model but can be coaxed to 500 MHz. --- End quote --- Would you have a pointer where to start looking for the "upgrade"? I scanned a few posts, so far unsuccessful |O --- End quote --- AFAIK it's the same process as SDG2000X models. Look there. Oh I saved a link, >:D follow this: https://www.eevblog.com/forum/testgear/unlocking-late-unit-sdg2042x/msg4639576/#msg4639576 |
| nctnico:
--- Quote from: Martinn on October 04, 2023, 07:29:13 am --- --- Quote from: tautech on October 04, 2023, 07:20:47 am ---As Mike pointed to earlier SDG6000X and entry into this range is 200 MHz model but can be coaxed to 500 MHz. Then with your DSO old school Bode plot to 300 MHz would be very possible like Dave shows in this old video: --- End quote --- I also considered signal generator+DSO, but instead of the crude sweep method Dave shows I thought of running a sweep via remote SCPI control. Set frequency, acquire reference and output channels, calculate amplitude/phase, next frequency. But that would be a lot of work to do the interfacing and the basic sweep method might be good enough! I will definitely look into the SDG6000X! --- End quote --- The downside of using a DSO is that bode plotting is pretty slow where it also differs between manufacturer. With the same settings, Siglent bode plotting is 5 times slower compared to the R&S RTB2004. A VNA is about 5 times faster compared to the RTB2004. So if you need to make a lot of measurements, using a VNA is a better option. |
| joeqsmith:
--- Quote from: Martinn on October 04, 2023, 07:01:50 am --- --- Quote from: joeqsmith on October 03, 2023, 11:18:39 pm ---Are you inferring that the VNWA3 does have a leveled output that can be adjusted? Does it also have sinewave drive? None of the low cost ones I have looked at do. They also don't have bias Ts, are only 2-port 1-path ..... Physical size, you never mention what sort of amplifiers but just thinking if you were playing with something in the kW range, I imagine the attenuators will be much larger than the VNA. --- End quote --- Yes, VNWA has an adjustable output. See this document on page 241: https://www.sdr-kits.net/documents/VNWA_HELP.pdf Here's an example of what I want to accomplish: https://www.eevblog.com/forum/projects/measuring-switch-mode-supply-noise-hp461a-replacement-ada4895/msg4652395/#msg4652395 The last graph (frequency response up to 200 MHz) was measured using a VNWA. Power levels are small signal only, so no kW attenuators. To my knowledge none of the low cost (< $1000) VNAs have a sine output (VNWA3 certainly does not). If you know of a RF signal generator with sine output and programmable attenuator for < $2000, let me know. --- End quote --- Thanks, I will read the document. I can't be much help on new equipment purchasing as all of mine is old. $2000 isn't much of a budget. I assume if you only want a signal generator and not an entire turn key system, you are planning to write the software or you need something that works with what ever receiver you own and their software. *** Skimmed the data sheet for their synthesizer. If you like the VNWA3 and can use the squarewave drive, can you get away with just getting a step attenuator with one of the low cost VNAs? https://www.analog.com/media/en/technical-documentation/data-sheets/ad9859.pdf |
| mawyatt:
--- Quote from: Martinn on October 04, 2023, 07:24:01 am --- Yes, I am thinking more of high impedance amplifiers, like this small design: https://www.eevblog.com/forum/projects/measuring-switch-mode-supply-noise-hp461a-replacement-ada4895/msg4652395/#msg4652395 But where do you see the problem with 50 ohms? High Z input can be terminated with 50 ohms (input noise changes of course, but that's not relevant here). Output needs to be capable of driving a 50 ohms load, which might be more of a problem. I had to include cable drivers in my "HP461A" LNA design. --- End quote --- Our comment was related to measuring a high impedance, here using a high impedance measurement instrument such as a DSO is generally better than a low Z device like a VNA. WRT to driving a low Z, most AWG generators and signal sources are fully capable of such. We have "enhanced" our SDG2000X and SDG6000X AWGs to full capability as mentioned. Both are superb performers, producing clean, accurate waveforms from 16 bit DACs, the UI is a little quirky tho, but one quickly gets used to such. Either can be employed with our SDS2000X+ for Bode functionality to 120MHz. The Bode implementation is quite good and allows user to control the input signal level across the sweep, and dynamically controls the measurement (scale factor on Ch 2) to achieve a wide dynamic range. rfloop had demonstrated quite remarkable DR for this core 8 bit DSO in Bode function, can't remember where this is but search for Bode Plot should revel such. Here's an example of using the SDS2000X+ and SDG6000X, note we are using in scope 50 ohms for Channel 2 and simply interfaced via LAN. Edit: Since we had this setup, decided to measure a Bourns 3590s 10K multi-turn precision pot set for 20dBV attenuation, note the complex frequency dependent behavior reveling the inductive nature of the resistive windings and the deep notch around 70MHz indicating a resonance within. Anyway, hope this helps. Best, |
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