Ground resistance measurements



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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