Topband: How to determine impedance

[Mike Waters]

Hello Martin,

I have other equations here:
www.w0btu.com/bev_ant_impedance-math.html

Other charts, matching transformer ratios, etc. are on
www.w0btu.com/Beverage_antennas.html

73, Mike
www.w0btu.com


On Wed, Jan 24, 2018 at 5:27 AM, Martin <dm4im at t-online.de> wrote:

> Topbanders,
> for the construction of the beverage ( a 2 wire reversible beverage, that
> is) from my post a few days ago i wanted to know how to measure or
> determine the impedance of the open wire. I stumbled across a very simple
> method some of of you might know , some might not. Anyway, here is the
> method. It works for coaxial cable or open wire.
> You need no fancy measurement gear-  rule, pocket calculator and LC meter
> will do. For really long runs you might need the help of a tape rule or
> even google maps.
>
> Measure the length of the unknown coaxial cable or open wire (DUT Device
> under test) in meters m.
>
> With both ends open, measure capacitance C of DUT, divide it by it's
> length ( C' = C/m) .
>
> Shorten one end, measure inductance of DUT, divide it by length ( L' =
> L/m) .
>
> Now calculate
>
> Z= 1000 * squareroot(L'/C')
>
> Voila.
>
> It may also help to determine if and where your cable or 2 wire beverage
> has an intermittance when you already know it's impedance it had before the
> failure. Transform the formula accordingly.
> I think it should also help to determine the impedance of the beverage (
> single wire or 2 wire) measured against ground(?).
>
>
> --
>
> Ohne CW ist es nur CB..
>
> 73, Martin DM4iM
> ____
>