In article ,
Greg Esres wrote:

A student recently installed a Garmin 430. It will not pick up a
nearby VOR on the ground, while his old 170B will.

Say what you want about the miracle of modern electronics, but the
KX-170 was a hell of a fine radio.

The needle comes
alive just after liftoff, but it does seem to have a lot of course
roughness.

His localizer also exhibits a lot of course roughness when far out on
the localizer, say, 15 miles. In visual conditions, I could see the
airport off to our left, but the needle was centered. Shortly
thereafter,the needle moved left and he corrected to what appeared to
be truly the extended centerline of the runway.

I'm not comfortable with this aircraft in IMC until I'm assured the
course guidance is rock solid. Any thoughts as to what might be
causing these indications?

I'm going to guess the antenna. One of my club's CNX-80's had one of
the legs of the nav antenna (V-style on the vertical fin) fall off. It
exhibited similar symptoms to what you're describing, until the antenna
was repaired.

I agree with you about not taking it into IMC until it's fixed, for two
reasons. First is the obvious (you might get killed). Second is that I
think a lot of what an instructor teaches is attitude and judgment, and
you do that by demonstrating, not by talking.