Reg Edwards wrote:
For example, in a large number of cases the single output quantity is
related to line loss, such as insertion loss in dB, or load power in watts,
or transmission efficiency in percent, or percent of input power lost in the
line itself.

But before this can be calculated it is essential to calculate input
impedance Rin+jXin for given attenuation in dB or nepers, given phase shift
in radians and given terminating impedance Rt+jXt. Then include generator
impedance Rg+jXg and internal generator volts. Having done this you are
half-way through.

Well Reg, I have a question about transmission line losses expressed in dB.
As you know, furnishing line losses in dB implies a power ratio. For a matched
line, transmission line losses in dB will be based on the ratio of power
not delivered to the load Vs the power being sourced. For instance, if
100 watts is being sourced and 95 watts are accepted by the load, then
5 watts of the 100 watts are line losses, or ~0.21 dB.

But to what power are the transmission losses referenced when reflected
power is allowed to be incident upon the source. For instance, assume
that at the source, we are reading 100 watts forward power and 85 watts
reflected power. That means the source is supplying a NET power of
15 watts to the system. If 10 watts of the total NET power of 15 watts
is being accepted by the load (implying 5 watts of line losses) does
that mean the power ratio for line losses is 33%, or 1.25 dB of losses?

Note from the matched line example above where 5 watts of line losses are
0.21 dB to the mismatched line example where 5 watts of line losses are
1.25 dB (for the same forward power of 100w), the same magnitude of loss
appears much higher as a dB value referenced to NET source power.
--
73, Cecil http://www.qsl.net/w5dxp