Hello, I am going to build a ground plane for the helical antenna to see if it improves the signal acquisition. I am thinking the plate should be in contact with the sma connector shield/outer shroud. is this correct?
No - the word āgroundā in this case isnāt referring to electrical grounding, but rather the physical groundā¦the ground plate/plane is meant to prevent reflected signals from bouncing off the ground and making their way to the antenna; it acts as a shield for interference, blocking signals from below
You donāt need to worry about actually grounding it 
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It is not quite clear what you are intending to do, but depending on the antenna design, a ground plane can help quite a bit to improve range and directionality. Without knowing the details of your helical antenna, there is no point in making any claims.
For example, a straight, 1/4 wavelength whip (straight wire) will perform about as a well as a 1/2 wave dipole, if a ground plane perpendicular to the base at the antenna feed point is present. And yes, the ground plane is grounded with respect to RF (the outer woven shield of coaxial cable leading the the whip).
Plenty of info on antenna design can be found on the web, mostly hosted by amateur radio operators. Example of ground plane theory and modeling
@jremington - In the GNSS world, ground planes are used a bit differently. Itās important that signals travel only directly from the satelliteās antenna to the receiverās antenna, not impacting anything along the way. Signals that bounce off buildings, trees, or up from the ground travel farther than those that travel directly, and the combination of line-of-sight and non-line-of-sight signals can result in significant performance degradation in the receiver. A metal plate under the antenna helps block signals bouncing up from the ground, as well as those very low on the horizon.
Here are a couple of good resources if you want to learn more:
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Thank for the links, I searched around yesterday for some info but came up short. This helps a lot.
Perfect thank you. This response plus the links millerjs2 added are very helpful.
Thanks for the links.
The use of the phrase āground planeā in GNSS is unfortunate and confusing, as it has a completely different function than the ground plane concept used in practical antenna design. In fact, in GNSS usage it describes the exact opposite concept!
[the ground plane] is made of any material that attenuates (or totally blocks or reflects) RF signals. It creates a shadow area for the antenna to hide in.
While that makes perfect sense, in antenna design, efficient reflection of RF by a conductive surface is used to extend the effective antenna length.
Very interesting and thanks for pointing this out. Yes, itās backward from convention. The GNSS use seems to be a barrier occlusive to RF: shielding, and doesnāt itself influence the transmitters or receivers.
In traditional, two element antenna design for terrestrial distance and fidelity, ground planes are sought and improved to āpullā signals toward the plane, to flatten the patterns toward the horizons and away from wasted UP and DOWN directions.
For example, those very large and visible AM radio broadcast antennas have acres of wire or mesh buried at their bases to form something like an RF disk so that the output pattern is more like a sliced bagel crown, the top half a toroid. Itās not always a plane, sometimes just a single element (like old tv rabbit ears) or bumpy structural member (like the bridge and deck of a ship) completes the path at the expense of that nice hemibagel shape. The better term counterpoise is also used. When I key a walkie talkie, the antenna radiates against the counterpoise that is made up of the mass that makes up the rest of the radio electronics, the battery, even my own body might couple a little bit.