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X-Dipole: Simulations for 500KHz (600m).
(Calculations performed using EZNEC+ v5.0)
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Simple dipole feed: N and S wires driven. E and W wires unconnected. Model: x45_dipole_600m.ez . |
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Polarisation is horizontal from broadside direction and vertical
from end-on. Radiation pattern is typical for a low electrically short horizontal wire. |
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Eficiency is low but acceptable. Zin = 6 - j1400 W at 500KHz A large series loading inductance will be required in the antenna matching network (further reducing the efficiency). |
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Splayed dipole feed: Field strength pattern is practically identical to simple dipole but rotated through 45°. Model: x45_splay_600m . Zin = 3 - j700 W at 500KHz Max gain: -13dBi. |
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| N+W driven against S+E gives vertical polarisation in NW - SE Direction (end on) and horizontal polarisation in SW-NE direction (broadside). |
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Double-T feed: Strapping the antenna to make two long wires which cross at the centre, and driving the two wires in opposition, produces a null in the vertical direction. Model: x45_2T_600m.ez . Zin = 2.4 - j730 W at 500KHz The disadvantage of this configuration for 500KHz working is extremely low efficiency (max gain: -37.4dBi). |
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| Polarisation is vertical in N-S and E-W directions (looking end-on to either wire), and Horizontal in NE-SW and NW-SE directions. |
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© D W Knight 2008.
David Knight asserts the right to be recognised as the author of this work.
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