Measurement Tables for Spiral Load Aerial evolution (1)

The first table is the measurement for the basic spiral aerial. The spiral inductance was 169uH and the downlead was about 30 feet long. The natural resonance of this assembly was at 1741kHz..

Frequency

in kHz

 Capacitance

in pF

 Resistance

in ohms
122 147.7 83.1
150 143.8 57.6
220 146.5 37.7
300 144.8 27.4
400 148.5 23.5
500 147 21.1
600 149.5 19.4
700 154.6 19.6
800 160.5 18.5
900 165.6 19.6
1000 174.3 24.9
1200 197 34.8
1400 243 56.9
1600 410 90.9
1700 956 98.8

The following table gives the measurements for the basic spiral with the inductance short circuited, so that the spiral just ascts as an extended capacity 'hat'. The natural resonant frequency of this configuration was 3502 kHz..

Frequency
in kHz		 Capacitance
in pF		 Resistance
in ohms
122 143.6 82.2
150 143.8 66.2
220 142 44.2
300 142 33.4
400 146.2 26.4
500 145 23.2
600 149.4 21.5
700 150.8 20.0
800 153.8 19.1
900 155 18.7
1000 155.8 20.7
1200 163.8 29.8
1400 173.8 53.5
1600 177.7 58.9
1700 173 65.7
1750 180.5 65.7
1800 181.0 64.4
1900 189 56.8
2000 194 57.2
2400 224 34
2522 242 34
3168 607 35
3300 1029 34.4
3400 1849 35.5

The next configuaration measured was the basic spiral inductor with a meander wire of total length 36 feet (11m) added as a capacity 'hat'. This addition reduced the natural resonance to 1348 kHz.

Frequency
in kHz		 Capacitance
in pF		 Resistance
in ohms
122 164.4 100
150 163.3 63.1
220 164.5 43.3
300 165.2 39.4
400 168.9 36.6
500 172.4 36.9
600 178.5 36.6
700 186 39.7
800 196.6 43.1
900 210 42.8
1000 236 40.5
1200 391 50.9
1300 862 69.9
1325 1339 74.6
1340 4930 70.3

The next configuration was to make a neated job of the capacity loading, and to that end 16 wires were connected from the peak, 4 to each side of the spiral periphery, terminating well clear of the spiral wire to avoid any corona effects if the aerial was powered up. The natural resonance dropped to 1147 kHz.

Frequency
in kHz		 Capacitance
in pF		 Resistance
in ohms
122 178.3 66.4
150 177.5 54.2
220 179.5 38.3
300 183 31.4
400 187.1 26.9
500 195.1 25.5
600 203 24.9
700 219 25.6
800 244 25.1
900 294 27.8
1000 409 34.3
1100 980 31.0
1120 1584 45.5
1136 2940 49.2

Click here for the next table with measurements of the double spiral version.

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