Cargo Containers

[RickM15752]

Anyone have experience installing low voltage wiring in outdoor cargo containers being used for storage? I've been asked to install a security system in an outdoor cargo container that has "electrical" already installed. I've not seen the job site yet. My only issue of concern is installing a small GSM cellular antenna on the outside to handle alarm reporting and I'm not sure what grounding I'll find when I go look at the job. I usually put an outdoor bell in tampered box on the exterior of a building to sound the alarm and would do the same on a cargo container. I'm not sure about grounding for the GSM antenna. It's similar to a car antenna and some folks say a separate ground is not needed while others say a separate ground is required.

This area is in California in an area that is not prone to lightning storms. My thought is that if the container has electrical, and that was done properly, then it has a grounding electrode bonding the container itself, and installing something like a mobile antenna would be sufficient ground where it penetrates the container, like a mobile install.

Or, am I missing something?

 

[GoldDigger]

Two different reasons for a "ground" in relation to the antenna:

1. The antenna, particularly if it is single pole type, may be designed to be located tight against a conductive surface which will affect the impedance and sensitivity pattern of the antenna. A connection to that metal plane at the base of the antenna is required for the signal going down the coaxial cable from the antenna base to be as designed.
For this is does not matter (except for directionality) whether the large metal plane is the ungrounded roof of a car or the grounded or ungrounded face of a shipping container.
2. There may be a provision for dealing with static electric or lightning induced voltages imposed on the antenna. As long as the body of the receiver and the rest of the system wiring is ungrounded or referenced to the body of the shipping container, it does not matter whether the container itself is connected to actual earth ground.

Discaimer: This is just theory, not experience.