Topband: How to determine impedance

[Martin]

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