How to ground FM antenna?

I think this is the antenna I'm installing. The previous one was just a length of that flat dipole wire laying in the ceiling cavity. It performed OK, but not great. I'm guessing my aluminum siding may have hindered it some. At any rate it got mostly pulled out when I was replacing the stereo. I thought it would be less challenging and more rewarding to install an antenna that actually stood above the trailer. I'm not so sure the ground plane is really that necessary for an antenna that's only receiving.

If the antenna reqires a ground plane, the FM band is roughly 3 meters (100 MHZ is 3 meters) so your ground plane needs to have a 1/4 meter radius,

So a simple disc of window screen, foil or other metal (Copper screen is best, well Silver or gold is best but, hey, let's be reasonable) roughly 19-20" in diamater with the antenna mounted in it's center. lay a thin layer of Dicore caulk on the roof, mount the antenna, press the screen into the Dicore and add a 2nd layer to smooth it down.

What is the antenna for? What configuration is it? Pic?

You may be able to add an artificial ground plane.

You can use your Winegard Batwing and a splitter.

You say "real" FM antenna... I assume that it's a folded dipole residential antenna? If thats the case it will have a 75 ohm output.. Plug coax into it and call it good

The major drawback of using a signal wire to ground is that the ground plane is then in reference to the plane of the device, not in reference from antenna, directly to ground. This may cause problems and may not. If it's easier to install, try it and see if you have a problem. If not, carry on and many happy tunes in your future.

I use a J pole for my stereo and have the shaft of the copper J pole attached to a holder on the aluminum siding, essentially a path to ground. The J-pole is a good design, it can be tuned for frequency and is fairly sensitive. I don't have the gear to measure the gain but my experience at my home location shows a great improvement.

We could discuss the topic of lightning regarding antenna ground but that is a can of worms.

You'd get the best results from using a non ground plane antenna up there like a dipole or other design. It will work to hook it to the vehicle frame through the 12v ground, but not as well as if it were on at least a quarter wavelength of metal or radial system that then hooked to the ground.

Jim