Sunday, January 15, 2012

Station Grounding: An Introduction

Properly grounding a radio station is far more important than is usually discussed in most ham radio license classes.  A number of problems may arise from a lack of, improper, or poor grounding.  First, there are two kinds of grounding to be managed in a radio station, signal ground and safety ground.  These are not one and the same, but they are integral parts essential parts of any station installation.  This discussion will not go into detail of grounding techniques.  It will discuss, however briefly, some things that may result from grounding problems. 

First, Safety Ground

There are two aspects to safety ground.  Most importantly it protects you, your house, and others from electrical shock or possible fire due to faulty equipment.  It provides the path by which fuses are blown should a dangerous condition occur in any piece of electrical equipment.  Secondly, it provides a path to dissipate high voltage that may happen due to a lightning event.  Notice I did not say lightning strike.  In truth there is almost nothing one can do to prevent damage from a direct lightning strike.  The best we can hope to do is mitigate the circumstances that lead to a lightning strike.  In other words we make high objects less attractive to lightning by providing pathways to dissipate static electricity to ground before it can build to critical levels. 

Second, Radio Frequency Ground

Turns out RF ground can be much more complicated to manage than safety ground.  However, the lack of or a poor safety ground can almost assure that a station will have RF ground problems.  This is particularly but not exclusively true to frequencies below 30 MHz.  So what are some of the problems you may encounter? 

You may have or develop RF in the shack.  That is a condition where the metal surfaces of some or all of your equipment may exhibit radio frequency radiation.  This is most often noticed when you touch the metal parts of your station equipment and get a RF burn or at least it feels hot as in temperature not an electrical shock.  In less severe cases you may notice that your SWR changes when you touch the station equipment.  In fact you may not even have to come in direct contact to see the SWR fluctuate some.  Another indication is you may have someone tell you that your audio sounds bad or is poor quality[1].  It may show up as a buzz or distortion.  RF in the shack can manifest in a number of ways, but the ones listed are the most common.  In any case RF in the shack is to be avoided.

Details and references to help with grounding issues will come in other postings found under the Grounding label on this blog.

ARRL has a number of references that can be reach by starting with this link.

[1] - On VHF/UHF a condition called multipath may also cause very poor or unreadable audio.  However, this condition will cause both your transmitted and received signals to sound bad.  And it usually only happens in a single direction.  Other stations in different directions will be just fine.

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