Does an NMO mount require electrical ground?

[jsneezy]

The weather here in AZ is starting to tame down a little bit, so I'm finally getting ready to start my mobile install. I have a Midland "mirror and rollbar mount" for the NMO that I will be mounting to the side of a ladder rack I have on the truck. This mount from Midland has a pretty thick coating on it, which I'm not opposed to sanding down if need be, but I'm also not sure of how well the electrical ground between the ladder rack and the bed of the truck is. 

Does the NMO require an electrical connection to the vehicle ground through the mount, or is the ground through the cable to the radio sufficient? Every time I've tried googling the question, all I seem to come across is a bunch of answers about ground plane, which is obviously different. 

[axorlov]

1 hour ago, jsneezy said:

Does the NMO require an electrical connection to the vehicle ground through the mount, or is the ground through the cable to the radio sufficient? Every time I've tried googling the question, all I seem to come across is a bunch of answers about ground plane, which is obviously different. 

NMO mount itself does not require electrical connection, obviously. Drill the hole in plastic, tighten the nut, done! You are not going to fry the transmitter if SWR is acceptable.

But detailed answer about your install will delve into ground plane. Depends on antenna you're going to use. 1/2 wave does not need ground plane. 5/8 wave does need ground plane but works acceptably without one. 1/4 wave may work without ground plane, depending on the shape and size of your counterpoise. And when I say "ground plane" I use textbook definition: conductive surface more that 1 wavelength in diameter (plane, see it?), perpendicular to the antenna. More info here: https://en.wikipedia.org/wiki/Ground_plane 

[Sshannon]

5 hours ago, jsneezy said:

The weather here in AZ is starting to tame down a little bit, so I'm finally getting ready to start my mobile install. I have a Midland "mirror and rollbar mount" for the NMO that I will be mounting to the side of a ladder rack I have on the truck. This mount from Midland has a pretty thick coating on it, which I'm not opposed to sanding down if need be, but I'm also not sure of how well the electrical ground between the ladder rack and the bed of the truck is. 

Does the NMO require an electrical connection to the vehicle ground through the mount, or is the ground through the cable to the radio sufficient? Every time I've tried googling the question, all I seem to come across is a bunch of answers about ground plane, which is obviously different. 

The electrical ground through the cable shield is sufficient.  None of the magnetic NMO mounts require you to scrape to bare metal.

[jsneezy]

14 hours ago, Sshannon said:

The electrical ground through the cable shield is sufficient.  None of the magnetic NMO mounts require you to scrape to bare metal.

My understanding was that magnetic mounts had some kind of capacitive grounding. Maybe that's just for the ground plane. 

The ground plane in my situation is another thing to deal with altogether. I have a 1/4 wave antenna, the Tram 1126-B. There's a 12' long piece of 1x1 square steel tubing that will be running next to the antenna, but I'm not certain I'll see a great SWR. Maybe I'll get lucky, maybe I'll end up ordering a different antenna. I just can't get away with a 1/2 wave or anything taller because of some of the places I have to go like parking garages. 

[Sshannon]

3 minutes ago, jsneezy said:

My understanding was that magnetic mounts had some kind of capacitive grounding. Maybe that's just for the ground plane. 

The ground plane in my situation is another thing to deal with altogether. I have a 1/4 wave antenna, the Tram 1126-B. There's a 12' long piece of 1x1 square steel tubing that will be running next to the antenna, but I'm not certain I'll see a great SWR. Maybe I'll get lucky, maybe I'll end up ordering a different antenna. I just can't get away with a 1/2 wave or anything taller because of some of the places I have to go like parking garages.

Capacitive coupling is only for the AC of RF. Capacitors block DC. No DC ground for your antenna is needed. 
However, poor electrical connections between body parts can be a cause of noise so people frequently bond body parts together with copper braids.