[TowerTalk] Understanding Coax Loss Measurements

jimlux jimlux at earthlink.net
Sat Nov 28 14:27:26 EST 2020


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)


More information about the TowerTalk mailing list