Proper grounding at communications sites is essential for reliable, error-free operations and for safety issues
related to both shock hazards and lightning strikes. Many sources of advice exist for how to best collect equipment
and power source grounds in order to mitigate crosstalk and power supply noise. As with any time a group of equally
qualified 'experts' expound on opinions regarding best practices, some information you find will be contradictory.
One of the most highly regarded guidelines is a 518-page document published by Motorola (Publication R56) titled
"Standards and Guidelines for Communication
Sites." Many essential topics have been included like site design and development, communication site building
and installation, internal and external grounding, power sources, surge protection devices, soil resistivity, and
electromagnetic interference. There are plenty of diagrams included to help explain installation techniques. It
is all worth reviewing by anyone involved with radio transmitters, receivers, antennas, power supplies, RF switches,
etc.
Motorola R56 Equipment Rack Grounding
Appendix A, "Electromagnetic Energy Information," discusses intentional and unintentional EM radiation, including
environmental evaluation, exposure standards and limits, and compliance analysis. It also contains engineering considerations
like antenna elevation, collocated broadcast transmitters, location of directional antennas, antenna selection,
and mounting density of antennas.
Appendix B covers soil resistivity measurements that determine what kind of grounding system is required for
optimal operation. It outlines measurement procedures and calculation of results, which is used in Appendix D for
actually installing ground rods, metal mesh, and wires.
Appendix C gives a lot of insight into electrostatic discharge (ESD) causes and mitigation techniques including
wrist straps, flooring (ESD tiles and mats), chairs, operator equipment, relative humidity control, and how to develop
an effective implementation and monitoring plan.
This document has a current copyright on it and does not appear to be available directly from Motorola. I did
an online chat with a Moto rep and he could not find a location on the Motorola website where it can be publically
downloaded. He was aware, however, of the couple places on private websites where it can be accessed
(such as the one I have
hyperlinked) and did
not appear to be concerned about it.
I have to give credit to the ARRL's
QST columnist Joel R. Hallas (W1ZR) for bringing this
document to my attention.
Posted September 15, 2015
