# capacitance of transmissionline (magnifier)

`Original poster: =?iso-8859-1?Q?"Dieter_Böckeler"?= <Dieter.Boeckeler@xxxxxxxxxxx>`

Hi all,
I´ve calculated the capacitance of the transmissionline conductors in magnifiers
and I found a high value for the capacity.
I used the formula: C=2*Pi*E0*Er*L/ln(2*a/r)
E0=0,8854*10^-12 constant
Er for air=1
L=length of conductor (in metres)
a=distance to earth (in metres)
With the dimensions:
L=5 metres
a=1 metres
r=0,014 metres
I´ve calculated a value of 56pF.another formula gives a 10pf higher value.
rather high I guess.(is this formula correct?)
I calculated the surface of the conductor,and I got the same surface than a 14,7" ball,
but more capacitance.
On some magnifier sites is written about the fine tuning with transmissionline capacity.
But with such high values you can´t say fine tuning.
Another question is about coupling coefficient and effective coupling:
Keff=Kd*sqrt(L2/L2+L3)
and Kd=M/sqrt(L1xL2)
I read somwhere that the problem with fast quenching only occurs from the effective k.
Is this true?
best regards
alex