I have applied the suggestions and still can't manage to "tame the beast".

As long as the cap to ground from drain is in circuit the amp becomes
unstable at oscillates close to the centre frequency.

If I remove the cap the amp settles down but I loose tuning of the drain
circuit and the gain drops down.

I have a picture of the layout and schematic if anyone would be prepared
to take a look and see if there is something obvious.

The shield is placed right across the top of the BF998 to separate input
from output.
All component leads are cut as close to the component body as possible.

I also added another shield between G2 and the input circuit so the
input now is totally isolated from the rest of the ckt

Regards

David

Roy Lewallen wrote:
Your bypasses from G2 to ground and from the top of the drain inductor
to ground should be physically small, have very nearly zero lead length,
and connect directly to the drain or the bottom of the drain resistor if
used.

Roy Lewallen, W7EL