Dan wondered, in part:
"I have always wondered if antenna tuners really accomplished
anything. Even if the impedance of the rig is now matched to
the load does the swr between the tuner and the antenna just
eat up all the power in the form of heat?......."
Yes, the tuner does accomplish something; it matches the
Z's of the rig set up to the antenna system set up. The result
becomes the transfer of ALL the power from the rig output
into the antenna system. VSWR within the transmission line
up to the mis-matched antenna does not "eat up all the power".
The real part of the impedance of the line, which is pure R,
will "eat up" some power, in fact I-squared-R of it. But this
will amount to a small imperceptible loss. For example, on 20
meters, 14 mHz, 100 feet of RG-8 has a loss (due to the
Resistance of the conductor) of about 0.7 dB. Now, were
this line being used on 20 meters, and the VSWR on the line,
after the tuner, which cannot change the line VSWR, is,
say 3:1, the added loss, due to the multiple reflections caused
by the mismatch/vswr is an added, about, 1 dB. Or a total
line loss to all of your rig output power of 1.7 dB.
No one, anywhere in the world, would ever be able to tell
the delta between your rcvd signal were the system perfect,
or were you using an antenna tuner to cause full rig output
power into the antenna system with the 3:1 vswr.
For all the details about this, see the ARRL Antenna Book,
or even better yet, the soon to be published by Worldradio,
2nd Edition of Walt Maxwell's wonderful book, "Reflections."
Maybe a great Christmas present, if they get it out in time, hi.
Good luck and 73, Jim, KH7M
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