[TenTec] Wet ladderline

[Steve Hunt]

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



On 10/08/2013 00:55, Jim Brown wrote:
> 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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