[TenTec] Wet ladderline

[Steve Hunt]

Well, I just spent two hours re-calibrating everything; results using 
Zplots were marginally better, but still not acceptable.

Re-reading Dan's notes on Zplots'  "Measure Transmission Line 
Parameters" feature, he describes two methods: the first uses only S11 
measurements taken with open and shorted lines; the second method uses 
both S11 and S21 data in Touchstone s2p format files - presumably taken 
with the line terminated in 50 Ohms - on which he comments: "This method 
may be used for lines of any characteristic impedance; it is not 
restricted to just "50 ohm" type lines."

That comment seems to apply *only* to the second method, which means my 
attempts to use the first method on 450 Ohm line were doomed to failure!

In retrospect, I'm not too surprised that you can't extract the TL 
coefficients for high impedance line easily using S11 S/C and O/C 
measurements; you'd need to accurately measure impedances as high as 
30,000 Ohms!

The method I have been implementing manually looks similar to Dan's 
"second method"; but unfortunately the VNA2180 can't produce Touchstone 
s2p files, so I can't use Zplots to automate the process.

Looks like I'll have to revert to the manual number crunching :)

Steve G3TXQ





On 10/08/2013 09:36, Steve Hunt wrote:
> Jim,
>
> I'm comparing like for like: TLD's loss predictions for the line with 
> a 50 Ohm load, vs my measured results with a 50 Ohm load.
>
> I'm pretty sure my line is equivalent to Wireman 551, and therefore 
> would expect Zplots should deliver similar K0,K1 and K2 coefficients 
> to those Dan has for 551.
>
> I have a couple of hours free this morning so will re-run the open and 
> short circuit tests.
>
> 73,
> Steve G3TXQ
>
>
>