my reason was make narrow-band antenna. For reject all out of band
noise.

That is a very worthwhile objective. All that noise adds to the
intermod noise and the sooner you can stop it, the better.

In my youth I recall calling CQ on 42 mhz for a couple of weeks.
Fortunately, a very sharp yagi and very low power saved me from a
violation.

John Ferrell W8CCW
Beware of the dopeler effect (pronounced dope-ler).
That's where bad ideas seem good if they come at you
fast enough.