Clarifying a typo, "antenna tuners" like the KAT500 are networks that
transform the impedance presented by the transmission line to 50 ohms,
allowing the output stage to provide power to the line. This has NO
effect on loss in the line, which is determined solely by the match
between the antenna and the line, as Bob correctly states.
That said, line loss due to SWR is often wildly overestimated. For 60M,
I'm using an 80M dipole fed with about 160 ft of a good RG11, which
looks like 5:1 VSWR at the transmitter. Taking line loss into account,
VSWR at the antenna is around 7:1. A good transmission line calculator
shows the excess loss in the line due to VSWR to be about 1 dB, which is
a small fraction of an S-unit. Using FT8, I've confirmed more than 70
countries on that band with 100W, and can work EU almost any night from
my QTH near San Francisco.
73, Jim K9YC
On 12/4/2023 7:16 AM, Bob McGraw wrote:
The KPA500 at the station only matches the transmitter to the
transmission line and likewise for the receiver. It does not change
the match between the antenna and transmission line, thus the SWR and
related loss from SWR remains.
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