William E. Sabin wrote:
....

The coil in a CLC tee-type tuner can have a Q as high as 400, and stray
coupling to the metal cabinet or ground plane can easily cut the Q in half.
What effect that has depends on the load impedance of the antenna
feedpoint. If the load is highly reactive (high X, low R) the coil can get
quite hot.

I believe it is important that the open ends of the coil should be at least
one coil diameter away from any metal surface. The sides of the coil are
less critical, but the mechanical design should do a pretty reasonable job
of reducing that stray coupling to a low value also.

....
Hi Bill,

In practical tuner applications the unused part of the coil is usually
shorted. The reasoning is that it prevents the generation of high RF
voltages. Shorting part of the coil should ruin the Q quite a bit.
Any comment on this practice?

Thanks, Peter