Ground resistance measurements

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160-meter Ground Connection Resistance at W8JI

Clay soil, dry conditions, 20-foot tall hat element resonant on 160 meters. All radials 50 ft long except for test radial, which is 1/4 wl electrical insulated counterpoise.

 

Ground

Ground Resistance Ω

Antenna Resonance MHz

System change with resonant test radial

System change adding one additional  rod

Two 5 rods

85

1.944

Large over 50%

Rod has large effect

One radial NE

80

1.905

Large

Rod has large effect

One radial SE

80

1.905

Large

Rod has large effect

One radial NW

77

1.931

Large

Rod has large effect

Four radials

42

1.819

Moderate 50%

Rod has large effect

Three radials and two rods

50

1.819

Moderate 50%

Rod has moderate effect

Four radials three rods

54

1.820

Low 25%

Rod has noticeable but small effect

Seven radials three rods

29

1.875

Very low <10%

Rod makes very little difference

Eight radials three rods

27

1.880

Very low

Rod makes very little difference

 

Performance Indications of Test

Ground systems are reactive. Poor grounds can add reactance. This is shown by the resonant frequency shift as the ground system is altered.

In slightly moist clay pastureland soil it takes about 8 short (1/8th wl) radials to stabilize the ground impedance.

In slightly moist clay pastureland soil, two or three rods make a poor RF ground for low impedance antennas.

If you use four short radials on a vertical, it is almost like no ground at all.

With small radial systems, ground rods can actually increase feed resistance. Use this particular phenomena with some caution, since I did not sweep frequency!  

 

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