I make here reference to the well-known chart, shown in almost all the ARRL
Antenna Handbooks, setting the relationship among the real SWR (i.e. that
measured at antenna), the SWR measured at transmitter and the "line loss".

In the text they explain that the "line loss" to be considered when using the
chart is the line loss under matched conditions (i.e. that given by the line
manufacturer), that is without taking into account the extra loss caused by SWR.

They make the example of a line having a (matched) loss of 1.0dB with an SWR of
4.5 at antenna. The graph shows that the corresponding SWR at transmitter is
3.0.

Unless I am wrong, a simple calculation shows that, in the considered example,
the SWR at transmitter is about 2.3 rather than 3.0.

Here it goes (please note that, for the assumed SWR at antenna of 4.5, the extra
loss caused by SWR is just 1.0dB):

- actual loss on the forward wave: 1.0dB (matched) + 1.0dB (extra by SWR), for a
total of 2.0dB
- return loss corresponding to an SWR at antenna of 4.5: 4.0dB
- actual loss on the reflected wave: 1.0dB (matched) + 1.0dB (extra by SWR), for
a total of 2.0dB
- return loss at transmitter: 8.0dB
- SWR measured at transmitter (corresponding to a return loss of 8.0dB): about
2.3

It is interesting to note that the chart would give an identical result if by
"line loss" they would mean the total line loss (that is also including the
extra loss due to SWR) rather than just the matched line loss (as they state in
the text).

Any comment?

Thanks and 73

Tony I0JX