TABLE #2
(2) Values for distributed constants. Values for
distributed constants of commonly open-wire lines and
nonloaded cables are given in Table #2 below. Note that
as the wire diameter of an open-wire line increases the
series resistance decreases appreciably and the series
inductance decreases only slightly.
The shunt
capacitance increases slightly and the shunt conductance
does not change. This is because the shunt conductance
is actually leakage conductance and depends only on
the nature of the insulating material separating the wires. In the case of cables, only the series resistance decreases as the
wire size increases (lower gage number), the other constants remaining essentially constant.
59.
Characteristic Impedance.
The characteristic impedance, ZO, of
a network is the value of load impedance which
makes the impedance at the input terminals
of the network equal to the load impedance.
The tee and pi sections of figure 55 help
to explain this. For example, in the tee section
of A, the load impedance, ZR, is 600 ohms.
This resistor is in series with the right-hand
FIGURE 55. Tee and pi Sections Terminated in Zo.
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