Grounding Information

 

When we discuss grounding, we are not talking about a simple electrical ground provided by an eight foot pipe in the soil.  When working with RF vertically oriented antennas, a robust RF ground system must be employed.  This will include the necessary radial wire system discussed at this site.

Grounding Theory 

ground rodWhen operating on 160 a single ground rod will not work. You need to install a grounding system consisting of many radials all tied to a common point. This will provide excellent ground for RF and also can be part of your lightning protection. (An exception to this rule is if you are able to install a dipole or similar antenna that does not work against ground as a vertical does). Refer to the manuals and hand books shown below for more details on building your ground system for 160 meters.

We feel proper grounding (actually a comprehensive  ground system) is most important and most overlooked part of your 160 meter station. Hams often spend much time on their antenna and neglect their ground system. When working the higher frequency HF bands, the ground system may not be as essential as we find here on 160 meters. Thus hams become somewhat casual regarding the importance of a suitable ground system.  It is fortunate that when working on your ground system you can work on the ground!   Unlike some antenna system installations that may find you in a tree or up a tower.

The following links contain a wealth of information regarding grounding and your ground radial system necessary for your antenna system. Notice that we always include the grounding system as a main part of your antenna system. A pair of 8 foot ground rods will not suffice on 160 meters!


Example of a MINIMUM electrical grounding configuration (notice: RF radial system is not shown)

tower-grounding-dwg

The long radials for RF counterpoise attach to the tower base and could replace the shorter lightening protection wires shown in RED.  Of course the length and number of radials depends on the location and the performance tradeoffs.  See discussion below to evaluate what you might wish to install.


Your Grounding System: How Many Radials Do you Need?

The following data is from the 2005 ARRL Handbook. The article is by John Stanley, K4ERO, in his December 1976 QST article. This will give you the trade offs when designing your 160 meter grounding system.

Notice that case #6
(*)is deemed as the best configuration, one that is used by commercial AM radio stations (120 radials and over 4 miles of wire!) Note that the minimal configuration has 16 52 foot long radials has a 3 db signal loss over the
perfect situation – half your power is lost in the vertical antenna system (don’t forget losses in your feed line and antenna tuner!)

Configuration
1
2
3
4
5
6
Number of radials
16
24
36
60
90
120
Radial Length in feet
52
65
98
103
130
207
Spacing in degrees
22.5
15
10
6
4
3
Total radial length in feet
832
1554
2797
6216
11,655
24,864
Feed point impedance
52
46
43
40
37
35
Power loss related to #6
3 db
2 db
1.5 db
1 db
0.5 db
0 *

*this is deemed as the best configuration – set as the standard of comparison (this chart is valid for 160 meters only)

Summary: a configuration of 16 radials each 50 feet long should be considered the minimum acceptable ground system.



Smart Talk – RF Grounding by SGC.  Here are some general RF grounding tips for use with an SGC Smartuner (or any similar automatic or manual tuner):

  • Balanced antennas, such as a center-fed dipole or loop, do NOT require an RF ground.
  • Unbalanced antennas (verticals, whips, longwires, random wires or invered Ls) should have enough additional grounding to carry most of the RF current that might otherwise be returned by the lossy ground paths, so to minimize ground losses put down as much wire as you have room for.

 

  • If the grounding system will be mounted above the ground, a ground plane can be created with chicken wire or other grid material.
  • Unbalanced antennas mounted high in the air require a radial system or ground plane mouned below the antenna and connected to the Smartuner (or other matching device such as inductive matching) is just below the ground plane.
  • Indoors, ground wires can be run under carpets, along walls, or out of windows. But be very careful to isolate these eelments due to the potential high voltages.
  • We recommend a minimum of six to eight radials, but efficiency will increase with more. (See chart above) Remember to arrange them symmetrically to keep them from radiating.

Used by permission SGC, Inc.

 sgclogo


Installing radial wires

Polyphaser Lightning protection

W8JI web on grounding

Building a ground connection tester

Grounding Devices and Equipment

 

 Posted by at 4:45 pm