Re: Fast probe prices?


Jonathan Pyle
 

In the picture with the ringing, the 1S1 was set to 1ns per division. It's not a perfect sine wave but I would estimate the period of the ringing to be 750 picoseconds (1.3 GHz if my math is right).

Here are some more pictures of the setup:
https://groups.io/g/TekScopes/photo/262713/3205833?p=Created,,,20,2,0,0 (1S1 set at 0.5ns per division)
https://groups.io/g/TekScopes/photo/262713/3205834?p=Created,,,20,2,0,0
https://groups.io/g/TekScopes/photo/262713/3205835?p=Created,,,20,2,0,0

Since I've soldered an SMA jack right onto the probe (not something I'd probably do in practice) I think the grounding is probably about as good as it can get.

The yellow wire in the third picture, going from the SMA socket to the RF probe input solder pad, is about 0.375 inches.

There is a trace on the RF probe PCB that leads from a pair of capacitors to the output SMA socket, and it is about 1.28 inches long. So maybe that is acting as a ~12.8 nH inductor. The capacitors on the PCB are 1nF and 100nF in parallel, so maybe the circuit is like a 101nF capacitor in series with a 12.8nH inductor. I don't know what I am talking about, but if that's an RLC resonant circuit, I would guess it would resonate at a much lower frequency than 1.3 GHz. So maybe the ringing is from another part of the circuit.

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