For many years the ARRL Antenna Book has provided a table of conductivities and dielectric constants for common types of earth. Antenna analysis programs have adopted the values and they are widely used. However, ARRL never explicitly stated that they were for the AM broadcast band. Since ground parameters vary greatly with frequency, the ARRL values are not suitable for HF where they are commonly employed.
The ARRL data originally appeared in Standards of Good Engineering Practice Concerning Standard Broadcast Stations, which the FCC published in 1939.
I extrapolated the FCC ground parameters to the HF ham bands using the Messier soil model. The extrapolated values, while very approximate, should be more realistic at HF than the 1 MHz FCC values.
1.0 1.8 3.7 5.3 7.1 10.1 14.2 18.1 21.2 24.9 28.5
20.0 30.0 15.0 30.4 10.6 31.0 8.9 31.4 7.7 31.8 6.5 32.4 5.6 33.0 5.0 33.6 4.6 33.9 4.3 34.4 4.0 34.7
14.0 10.0 10.6 10.3 7.5 10.7 6.4 11.0 5.6 11.2 4.8 11.6 4.1 12.1 3.7 12.4 3.5 12.7 3.2 13.0 3.1 13.2
12.0 7.5 9.1 7.7 6.5 8.1 5.5 8.3 4.8 8.6 4.1 8.9 3.6 9.3 3.2 9.6 3.0 9.8 2.8 10.0 2.7 10.3
13.0 6.0 9.9 6.2 7.1 6.6 6.1 6.9 5.4 7.1 4.6 7.5 4.0 7.9 3.7 8.2 3.4 8.5 3.2 8.7 3.1 8.9
13.0 4.0 10.0 4.2 7.3 4.6 6.3 4.9 5.6 5.1 4.9 5.4 4.3 5.8 3.9 6.1 3.7 6.4 3.5 6.6 3.4 6.9
14.0 2.0 11.1 2.2 8.5 2.6 7.6 2.8 6.9 3.1 6.2 3.4 5.6 3.8 5.3 4.1 5.1 4.3 4.9 4.5 4.8 4.7
10.0 2.0 7.8 2.2 5.9 2.4 5.1 2.6 4.6 2.8 4.1 3.0 3.7 3.3 3.4 3.6 3.2 3.7 3.1 3.9 3.0 4.1
5.0 1.0 3.9 1.1 2.9 1.2 2.6 1.3 2.3 1.4 2.0 1.5 1.8 1.7 1.7 1.8 1.6 1.9 1.5 2.0 1.5 2.0
3.0 0.1 2.7 .12 2.4 .17 2.3 .19 2.2 .22 2.1 .26 2.0 .30 2.0 .34 2.0 .36 2.0 .39 1.9 .41
The figures are relative permittivity followed by conductivity in mS/m.
These are the Messier equations. σ is conductivity, εr is relative permittivity, σ0 is conductivity at low frequencies, ε∞ is permittivity at high frequencies, ε0 is the vacuum permittivity, and f is frequency. For each pair of FCC σ and εr values, I solved the equations for σ0 and ε∞ at 1 MHz and then evaluated them at HF.
Relative permittivity is simply permittivity below.
Seawater permittivity and conductivity are constant over HF but vary with salinity and temperature. In nonpolar regions, permittivity ranges from 70 to 80 and conductivity from 3000 to 6000 mS/m. Maps here and here show ocean conductivity but do not resolve coastal values. This map shows seawater conductivity along the U.S. coast (10 µS/cm = 1 mS/m). Use this map to find local salinity and temperature. Then download this program to calculate permittivity. Absent local data, 75 and 4500 mS/m are reasonable generic values.
ARRL lists freshwater permittivity as 80. It is constant over HF but varies with temperature:
°C °F Permittivity 0 32 87.7 5 41 85.8 10 50 83.8 15 59 81.9 20 68 80.1 25 77 78.3 30 86 76.6
ARRL lists freshwater conductivity as 1 mS/m, a low value. It is constant over HF but varies with temperature and location, e.g., 4 to 29 mS/m for individual Great Lakes and 20 to 100 mS/m for major rivers. This map shows local U.S. values (10 µS/cm = 1 mS/m). Absent local data, 15 mS/m is a reasonable generic value for a lake.
George Hagn of SRI International developed these curves in the 1980s based on ground measurements made in the 1960s.
1.8 3.7 5.3 7.1 10.1 14.2 18.1 21.2 24.9 28.5
■ 86.3 119 63.9 128 55.0 133 48.7 137 42.0 142 36.5 148 33.0 152 30.9 154 28.9 157 27.3 159
■ 59.8 40.2 43.0 46.9 36.4 50.7 31.9 54.0 27.1 58.2 23.2 62.6 20.7 65.9 19.3 68.2 17.9 70.6 16.8 72.6
■ 19.8 3.6 17.2 5.0 16.1 5.9 15.2 6.8 14.2 8.0 13.3 9.3 12.7 10.4 12.3 11.2 11.9 12.0 11.6 12.8
■ 13.4 .83 12.2 1.2 11.6 1.5 11.2 1.8 10.7 2.2 10.3 2.6 10.0 3.0 9.8 3.3 9.6 3.6 9.4 3.9
■ 11.0 .44 9.5 .61 8.9 .72 8.4 .82 7.8 .96 7.3 1.1 6.9 1.2 6.7 1.3 6.5 1.4 6.3 1.5
■ 4.7 .071 4.1 .10 3.8 .12 3.6 .14 3.3 .17 3.1 .20 3.0 .22 2.9 .24 2.8 .26 2.7 .28
Since it can be difficult to read precise values from the curves, the table lists permittivity followed by conductivity in mS/m for the ham bands. The 1.8 MHz values are extrapolations below the original 2 MHz limit.
Extrapolated FCC and Hagn values differ widely for similar terrain. At 14.2 MHz for example, FCC rich soil is 5.6/33.0 or 4.1/12.1 while Hagn rich agricultural land is 23.2/62.6. An average of 20 N6LF measurements for Oregon bottomland yielded 42.8/35.0. OE1CGS measurement of very good Viennese garden soil one day after rain was 31.6/32.3. FCC for pastoral, medium hills is 4.0/7.9 or 4.3/5.8 while Hagn is 13.3/9.3. FCC for rocky soil, steep hills is 5.6/3.8. Hagn is 7.3/1.1, not far from the 5.9/1.3 average of two AE5CZ measurements in a sandy wash in New Mexico. The wash was at the foot of rocky, steep hills. The hillside electrical properties seem to have washed down with the sand. FCC sandy is 3.7/3.3. FCC city is 1.8/1.7 or 2.0/0.3 while Hagn is 3.1/0.2.
For best antenna modeling accuracy, use a ground probe to measure your soil. Otherwise use the Hagn values.
88–108 MHz