[TenTec] Wet ladderline

[Jim Brown]

Private email.

Quoting from your webpage, "I tried various methods to measure changes 
in loss, including driving the line with a known power and measuring 
changes in the current delivered to a load resistor. However, I found 
that the most repeatable method was to measure the line loss directly as 
an S21 measurement in a 50Ω system using a VNA2180 2-port Vector Network 
Analyser; then, having measured the input impedance of the line, to 
correct the S21 figure for the source mismatch loss."

It would appear from this that you did not correct for the excess 
attenuation due to the mismatch of the load to the line. Or did you make 
that correction and not notate it? That would certainly account for the 
difference. Remember that Dan's parameters are for a matched line, and 
are the same that Times uses to describe their cables.

Several years ago, I made point-by-point measurements of more than 1,000 
ft of some very good RG8 that is rather similar to LMR400, except that 
it has a solid copper center and a plenum-rated dielectric and outer 
jacket. That long length is gone, but I just made up a couple of 135 ft 
lengths for Field Day. I should measure those with my VNWA (I have that 
German one, very nice) and feed the data to Zplots and see how it 
correlates.

73, Jim K9YC

On 8/9/2013 1:56 PM, Steve Hunt wrote:
> Jim,
>
> Thanks for pointing me in the direction of Zplots - I'd not 
> appreciated what it can do, although I'm a big fan of AC6LA's TLD 
> software.
>
> I just downloaded Zplots and ran open and short S11 tests on the line. 
> I plugged the values Zplots gave me for Zo, Vf, K0, K1 and K2 into 
> TLD, however it then predicts losses very different from my measured 
> losses. But, interestingly, if I use TLD's default parameters for 
> Wireman 551 it predicts losses very close to what I measure!
>
> It's not clear to me yet why Zplots would give me line parameters so 
> different from TLD's parameters for Wireman 551.
>
> I need to explore this some more because if Zplots can produce 
> believable results it would save me a lot of number crunching :)
>
> Steve G3TXQ
>
>
> On 09/08/2013 16:55, Jim Brown wrote:
>> Another way to get transmission line parameters from VNA or VIA 
>> measurements is to measure S11 with the far end open and shorted, or 
>> to measure S21 and export the data to AC6LA's Zplots spreadsheet. 
>> I've used this with good results for 50 and 75 ohm coax, and for 
>> closely spaced parallel wire line in the range of 90 ohms.
>>
>> Although S21 data and S11 data should produce the same results, Dan 
>> told me that users of his spreadsheet reported more consistent 
>> results when S11 data sets were used. I've tried both, and agree that 
>> the S11 data sets are the better way.
>>
>> There's a lot of useful stuff on Dan's website. http://www.ac6la.com/
>>
>> 73, Jim K9YC
>>
>> On 8/8/2013 2:59 PM, Steve Hunt wrote:
>>> I managed to find time today to produce a web page on my measurements.
>>>
>>> For anyone interested:
>>> http://www.karinya.net/g3txq/wet_ll/
>>
>>
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>
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