You asked about 198kc Droitwich, This is a Marconi "T" supported by two masts, 180 mtrs apart(590 foot)
The 4 wire vertical cage radiator, is around 213 mtrs high (700 foot),
connecting to a 4 wire Capacity hat, that goes out 90 mtrs(300 foot) in each direction
So the vertical height, plus half of Capacity hat, is nearly a quarter wave, for resonance
The Vertical part, is well over an Eighth wave, but nowhere near a Full quarter wave.
(unlike 252kc that is nearly a quarter wave, with part of top set of stays, as a small capacity hat)
With Any Low freq. antenna, The worst place for a lossy loading coil, is at the feedpoint,
you can end up with more current flowing in the coil, than in the aerial itself= lossy
With a short vertical, the bit that's actually missing, is Not the Top bit, its the Lower bit,
So a huge base loading coil, is like the majority of the aerial, coiled up, with a short vertical just above it.
A radio ham in Ireland, Finbar, I think holds record for longest LF 136khz contact, using a spiral capacity hat.
As 70 percent of the output from a full quarter wave, comes from the lower down, higher current half,
the Droitwich 198 being over half the size of a full quarter wave, works really well
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