RadioBanter - View Single Post - where does the power when using an antenna-tuner go to ?

Ralph Mowery · July 11th 20, 03:14 PM posted to rec.radio.amateur.antenna

In article , says...

The reason I kind-of ignored resistive loss as that component is not
relative to frequency while the efficiency of an antenna+antenna-tuner
system is clearly frequency dependent.

It is however an interesting thought that power-dissipation due to
resistance can be frequency-dependent via its current.

But would this not mean that the efficiency of tuned antenna would be
dependent of the design of the tuner and that a theoretical
antenna-tuner without resistance would have 100 % efficiency.

The loss in the tuner is the loss in the components, mostly the
resistance of the coil. It could be some in the capacitors if they are
not a air or vacuum variatables ( switched in capacitors sometimes used)
It could also be in the internal wiring.

Tuners are only optimised over a small band of frequencies and
impedances. If one designs the tuner to be the best at 14 MHz, then the
coil and capacitors will be too large or too small at other frequencies
for optimen power transfer. That is often referred to the Q of the
circuit. YOu start to get larger and larger circulating currents in the
tuner and the losses go up due to the resistance of the coil and wires
in the tuner.

Look at transmitters of the old tube circuits. The plate circuit is
designed for a Q of around 10 to 12. That seems to be the best
compromise between the harmonic reduction and efficency. Go one way and
the losses go down, but the harmonics go up. Go the other way you
reduce the harmonics but the efficeny goes down.