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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator

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radiolistener:
pantelei4, just reviewed your screenshot, ok. I can agree, it looks like this is not the case when short pulse is hidden due to cable ringing. But who knows... Measurement with impedance match is more reliable  :)

So, FY6600 has 12 bit sine wave?

pantelei4:

--- Quote from: radiolistener on August 22, 2019, 07:47:45 pm ---So, FY6600 has 12 bit sine wave?

--- End quote ---
Yes.

rhb:

--- Quote from: maxwell3e10 on August 22, 2019, 03:07:05 pm ---All of this transmission-line considerations of cable impedance and load impedance matching apply only if the cable is long enough to be a transmission line, which means its length is comparable to the wavelength of the wave. With light speed on the order of 1 ft/nsec one doesn't need to worry about impedance matching for a 3-ft cable and 100 nsec pulses.

--- End quote ---

The above is completely wrong.

Here is a 36 ps rise time, 10 MHz square wave displayed on a 200 MHz Instek MSO-2204EA with a 50 ohm source feeding a 1 M ohm input.  This is one of the excellent units sold by Leo Bodnar.  There is *no* cable, just a BNC male connector mounted on the board.

Aside from the appearance of the square wave I call your attention to the measured rise time shown in the lower left corner.  Nominally BW = 0.35 divided by rise time.

 

The second  image is the same source and same scope settings except that the source is now connected using a 50 ohm thru termination 1.5" long and the gain adjusted.  Again, note the measured rise time in the lower left.

 


Just for good measure here is the same setup but using a 100 ps pulse instead.  The scope is in dot mode with infinite persistence.  The narrower impulse is with the terminator, the wider is without.  I'd like to point out that the pulse is only 1/10th the I GSa/s sample rate of the DSO for the benefit of those who claim that you can miss a short pulse if your sample rate is not fast enough.



maxwell3e10:
rhb, in all your work in the oil business, have you ever worked out solutions to Maxwell's equations in a cylindrical waveguide with a center conductor?

What you are showing is not really relevant, you are looking at rise times of very fast pulses with a bandwidth way beyond that of the equipment used. So, the rise time and wiggles is just a function of the oscilloscope input stage ringing. It can depend on gain setting, quality of BNC connector, even how it is rotated. Plus, one shouldn't always trust automatic scope measurements, the difference in those rise times is not a factor of 2. And to compare pulse width, they should be made the same height.

rhb:
I suggest you find a good primer on the use of oscilloscopes and read it.  In particular the section on input impedance and bandwidth.

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