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Comment by chongli | Hacker News Reader

Your article says "VNAs are very expensive." Does this mean something like the NanoVNA [1] is inadequate for this measurement?

[1] https://nanovna.com

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I do mention the NanoVNA as a measurement option that has better accuracy since it can do phase measurement. It's an amazing tool, though its lower limit for frequency is 50 kHz and I'm not sure how its dynamic range holds up there. Ideally you want the option to go very low for this measurement. Like most VNAs sold today, the NanoVNA is really designed for looking at RF and microwave circuits.

I only know two commercial VNAs in-production that are made specifically for this kind of work: the Keysight E5061B (5 Hz - 3 GHz, $50000+ when optioned out appropriately) and the Omicron Bode 100 (1 Hz - 50 MHz, I think $5k-10k).

I assume you don't actually need all of the transmission line s-parameters at low frequency. In which case, you can use a frequency response analyzer (FRA), of which there are a few in production. The gain and phase measurements are enough to plot transfer functions, impedance, Bode, and Nyquist.

The FRAs span the same price range as the VNAs you listed. Having a low-cost version of each can extend the frequency range over which you can make good measurements compared to just one tool of similar total price.

The Bode 100 sacrifices some low and high frequency range and performance to be a 2-in-1.

What sacrifice would you say that the Bode 100 makes in performance (Especially compared to the E5061B)?

All test equipment has reduced performance near its limits. I probably should have just said range because it's implied.

I think the Omicron Bode 100 is the best bang for buck for a proper VNA these days.

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