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| Bode plot up to a few 100 MHz |
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| tautech:
--- Quote from: mawyatt on October 04, 2023, 01:59:55 pm --- 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 reveal such. --- End quote --- Done exploring the Bode plot limits of the $499 SDS1104X-E paired with a Siglent AWG: https://www.eevblog.com/forum/testgear/siglent-sds1x04x-e-bodeplot-ii-(sfra)-features-and-testing-(coming)/ |
| tszaboo:
So instead of a vector network analyzer, you need a scalar network analyzer. There are some old HP units on ebay that would do this, but only if you can get a deal. Depending on your amplifiers, a VNA could be a bad choice. They expect 50 Ohm input and output, plus you can blow them up with just a bit of power. Considering you already have a nice 300 MHz scope, I would get a used signal generator, and program the thing up to make sweeps. Probably a Z0 probe would help on the scope side. Or you get the bonus round: Get a RF white noise generator to 1GHz, and record the bode plot with the FFT of the scope. |
| 2N3055:
--- Quote from: tszaboo on October 04, 2023, 09:17:57 pm ---So instead of a vector network analyzer, you need a scalar network analyzer. There are some old HP units on ebay that would do this, but only if you can get a deal. Depending on your amplifiers, a VNA could be a bad choice. They expect 50 Ohm input and output, plus you can blow them up with just a bit of power. Considering you already have a nice 300 MHz scope, I would get a used signal generator, and program the thing up to make sweeps. Probably a Z0 probe would help on the scope side. Or you get the bonus round: Get a RF white noise generator to 1GHz, and record the bode plot with the FFT of the scope. --- End quote --- Allow me a bit of pedantry here: If it is only magnitude plot (no phase info) than it should not be called Bode plot but simply frequency response plot... Just saying-- |
| tautech:
--- Quote from: 2N3055 on October 04, 2023, 09:49:02 pm --- --- Quote from: tszaboo on October 04, 2023, 09:17:57 pm ---So instead of a vector network analyzer, you need a scalar network analyzer. There are some old HP units on ebay that would do this, but only if you can get a deal. Depending on your amplifiers, a VNA could be a bad choice. They expect 50 Ohm input and output, plus you can blow them up with just a bit of power. Considering you already have a nice 300 MHz scope, I would get a used signal generator, and program the thing up to make sweeps. Probably a Z0 probe would help on the scope side. Or you get the bonus round: Get a RF white noise generator to 1GHz, and record the bode plot with the FFT of the scope. --- End quote --- Allow me a bit of pedantry here: If it is only magnitude plot (no phase info) than it should not be called Bode plot but simply frequency response plot... Just saying-- --- End quote --- Sure with a through measurement of an active device one needs be careful VNA input limits are adhered to but Phase measurements with cheap VNA's are certainly possible and often the # of measurement types exceed the # of traces available. Quick example from a random selection of antennae tested in this thread: https://www.eevblog.com/forum/rf-microwave/what-really-is-this-antenna/ |
| joeqsmith:
My software for the LiteVNA supports Bode, stability circles .... You stated that the squarewave drive is no problem for you. I think the issue is that the Lite's output isn't leveled. From min to 500MHz, the one I am looking at changes about 3dB. If you were trying to measure say where the amplifier was starting to compress and you were using a wideband like this, I think you would run into problems. You give up a lot of basics when you only pay $120. |
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