I have seen measurements of homemade calibration loads. optimum was 2 resistors of 100 Ohm in parallel. It performed better than a single 49R9 resistor or 3 x 150 Ohm resistors.
Some interesting links:
Couldn't find the link evaluating different load styles.
Op 7-3-2024 om 16:52 schreef Brian Beezley:
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When considering a VNA calibration load for various projects, I used to specify two 100-ohm 1% resistors in parallel, which halves stray inductance. Of course it also doubles stray capacitance, which may be a worse problem. So I started specifying a single 49.9-ohm 1% resistor. I was surprised to discover that 50-ohm 1% resistors are available. I was really surprised when I noticed the price for 0.1% parts:
It's unlikely a NanoVNA application needs 0.1% accuracy, but the parts are so cheap, why not? If you look at the Vishay datasheet for the first part,
you'll see graphs for resistance magnitude and phase angle for several part sizes, most to 3 GHz. The curves look pretty good.
I've never actually used these parts, but they look good on paper. Maybe others can comment on their experience with various noncoaxial VNA loads.
Brian
