[TowerTalk] K9YC Choke Cookbook Question

[Jim Brown]

And with the easy availability of powerful test gear at relatively low 
cost, combined with AC6LA's fine Excel spreadsheets, it's easier than 
ever to get good data for VF and Zo vs frequency from a few measurements.

The procedure is pretty simple. Make swept vector impedance (that is, 
complex, magnitude and phase) of a convenient length of the line, one 
with the far end open, again with it shorted. Export that data to the 
spreadsheet, which will then compute and plot curves of VF, Zo, and 
attenuation vs frequency. The AIM family of analyzers will do this, and 
I believe the SARK will too.  My weapon of choice is the VNWA 3e, 
designed by German university EE prof DG8SAQ and built by some hams in 
the UK.

The effect of a CCS conductor is clearly seen by comparing plots of mfr 
data for CCS cables on the same graph as for cables with a solid copper 
center. CCS line has more loss below 10 MHz than copper.

73, Jim K9YC

On Sun,2/5/2017 7:24 PM, Wes Stewart wrote:
> If you follow this link http://k6mhe.com/n7ws/Ladder_Line.pdf to my 
> paper and look at Table 1, it gives the measured values of four 
> different Wireman P/Ns.
>
> Note that these are 50 MHz values and transmission line Zo and Vp are 
> anything but constant at lower frequencies.  Likewise, these 
> particular lines use copper-clad steel conductors that "misbehave" at 
> lower frequencies so Eq 4 somewhat falls apart when the conductors do 
> not have a well-developed skin effect. I mentioned this in the paper 
> but did not account for it in the equation.
>
> Wes  N7WS
>
>  On 2/5/2017 5:11 PM, Hardy Landskov wrote:
>> Hi Jim and all,
>> The email below reminds me of a problem I had some years ago with 
>> "450 ohm
>> window line". Nothing seemed to work. I then found an article that 
>> explained
>> how to measure the Zo of coax/ladder line. I measured a piece of 
>> window line
>> and it was 374 ohms! I found out in the archives that W8JI had 
>> measured 377
>> ohms with a piece of window line. We exchanged emails and he was 
>> elated that
>> I had verified his results.
>> Here you have two different sets of equipments, two different runs of 
>> ladder
>> line, and different times. I was very happy myself. I have an HP8753B 
>> so it
>> was no problem to run through the numbers. It was a very eye opening
>> exercise!!
>> Bottom line: Use 375 ohms for matching tuners and other things when 
>> using
>> this line.
>> 73 Hardy N7RT/4
>>
>
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