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Re: HI-Z EVALUATUTION - MEASURED DATA COMPARISON with HP 8753C

 

Robert,

please take a look at my 9.8k Ohm measurements. With the S21 method, the
results are acceptable.
/g/nanovna-users/message/11027

For a lower resistor, results are much better (S21 method):
[image: image.png]

Using an external bridge with a reference higher than 50 OHm would improve
measurements, but some difficult calculations are needed.
/g/nanovna-users/topic/64426024#8601

Ady YO2NAA

On Tue, Feb 18, 2020 at 4:53 PM W1RS <Deflatermaus@...> wrote:

Nels, I should have said Hi-Z broadband transmission lines. Of course the
tube amp situation is as Dave stated. I went to
to calculate the spacing
for the ladder line.
I was amazed at how rapidly it increases with the impedance. The
line-to-line capacitance requirements just get really small. According to
the equations presented,

300 Ohms --> 0.3 "
450 Ohms --> 1"
700 Ohms --> 8.5 "
1000 Ohms --> 105"

I'm very impressed with the nanoVNA, but with the 50 Ohm bridge design, I
would not expect to achieve good accuracy at measuring at greater than 10
times the bridge Z, especially at higher frequencies.



image.png

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