If I use the VNA with direct input of ladder line, say nominal 450 ohm Zo, but
with measured parameters more near 400 ohms, should I not run OSL calibration
with a 400 ohm load prior to running the sweep?
The response below seems to imply that calibration with a 50 ohm load will
yield “good results for coax and two-wire line of any impedance?”
Or does the creation of a reference plane with 50 ohms in the OSL calibration
yield results for a wide varieties of feed line?
Basic question.
Best from the West
AG6CX
Sent from my iPhone
>> On Nov 28, 2020, at 11:27 AM, jimlux <jimlux@earthlink.net> wrote:
>>
>>> On 11/28/20 11:08 AM, Jim Brown wrote:
>>> On 11/28/2020 3:43 AM, Kirk Kleinschmidt via TowerTalk wrote:
>>> I'm trying to characterize some coaxial cables and various connectors, and
>>> the results from my two measuring methods aren't reconciling well. My
>>> understanding of the tools is also less than complete.
>> First, make sure that your VNA is well calibrated. For cailbration, you will
>> need standard Open, Short, and 50 ohm parts.
>> Then, use it to make S11 measurements over the frequency range of interest.
>> I'd go with 1-50 MHz. Then download a copy of AC6LA's ZPlots Excel
>> spreadsheet, export your data to it, and follow his instructions for
>> characterizing the cable.
>> This will give good results for coax and two wire line of any impedance.
>> 73, Jim K9YC
>
>
> A bit of background: AC6LA's spreadsheet does the renormalization for the
> different impedance, if your VNA doesn't have that feature.
>
>
> (you're not using the NanoVNA, but for those who are, the NanoVNA-Saver
> python program also has the "change characteristic impedance" feature)
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