[Roadsters] Jumping jack tac

[stan]

Hello all,
I seem to have a tac that jumps all over the place from low idle to
about 2500 RPM.  It just bounces up and down.
Once I rev it up past 2500-3000 it smoothens out and gives me an
accurate reading.
 
I have a 69-1600.  Is this normal?  If not, what could possibly be the
cause(s)?
 
I would appreciate any help.
Cheers!
 
Stan
Coquitlam (just outside of Vancouver), BC