A revised attempt at simulating the Miracle Whip on top of a 20m 1/4 wave bottom half of a dipole, employing an emulation of the impedance transforming, base loading and inherent loss of the CVAT autotransformer using parameters looked up in the table in "EZNEC Simulation of Miracle Whip Antenna and Extensions". The MW acts as the shortened half of a vertical dipole. The lower half of the dipole is the radiating braid of the coax feedline with a common-mode choke at the 1/4 wave distance from the transformer.

The reader is directed to the aforementioned article and to the Antenna Notes associated with the EZNEC model "MiracleWhip on transmitter.ez" for more information on the CVAT emulation.

Wire #1 is the 57" whip, increased to 63" to compensate for the L-networks object insertion (see below) and simplified to a constant 1/4" diameter. Wire 2 is the 1/4 wave 20m counter-poise or lower half of the dipole and is nominally 16 ft. The simulated length below the insertion feedpoint is increased by ~6" split off from Wire 1. EZNEC 5.0 Demo is limited to 20 segments so the whip was allocated 5 and the 20m 1/4 wave below was given 15. Each segment is on the order of 1ft. The model starts with the bottom end of the dipole at 18" above ground, thus the dipole feedpoint is 18 ft. above ground, representing a practical portable configuration.

The L-networks object cannot be attached to the very end of a wire. It is inserted into the end segment of the whip "wire", in this case the first of 5 segments offset from the end by 10% or approximately 6". The length of the vertical was increased from 57" to 63" to compensate; there's nothing we can do about the 6" tail but allow it to be part of the lower pole of the dipole.

No claim can be made for the accuracy of the model. It has been neither sanctioned by nor validated by Miracle Antennas, the manufacturer of the Miracle Whip. The model is purely the invention of the author who shall not be held liable for any loss or damage that may ensue from anyone's use of the model or from the application of changes to the Miracle Whip antenna that may appear to work in the model. 

Tom Holden
VE3MEO
4 Feb 2009