Place the GPS antenna directly on the ground plane?

[Q]

I have Trimble embedded 3.3V GPS unpackaged antenna
and a home-made ground plane (60x60x1.3mm sheet metal);

Can I put the GPS antenna directly on the ground plane
(than the ground plane would contact with antenna's GND)
or place some dielectric between?
(what kind and size of dielectric?)

I have oem GPS receiver Lassen SQ;
Can I put that GPS antenna directly on it?

ps.
I read "Basic Guidelines for the use of the
Ultra-Compact Embedded Antenna",
but I didn't find there any info .