Thanks Jim:
But not sure which your “yes” addresses, part 1 or part 2?
1. “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?”
2. “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?”
Appreciate the clarification.
For example, Sark-110 allows you to select Zo, calibrate for 50 ohms, then add
or subtract feed line, with a menu of 50 to 450 ohm feed lines.
Thanks!
Ed McCann
AG6CX
Sent from my iPhone
> On Nov 28, 2020, at 2:02 PM, jimlux <jimlux@earthlink.net> wrote:
>
>> On 11/28/20 11:47 AM, Edward Mccann wrote:
>> 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?”
>
> Yes, if you use AC6LA's spreadsheet. It takes care of the 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?
>
> Yes, you can test anything with a 50 ohm reference cal, you just have to
> adjust for the non 50 ohm system you're testing.
>
> (one can spend a lot of time arguing about whether you'd be better off doing
> a cal with an impedance closer to your system impedance, but ultimately, it's
> the same measurement, just different math)
>
>
>
>> 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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>
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