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Stefan Johansson

The answer is in fact aviable at The Alexander association website however only in swedish.

After having selected using the swedish language website then in the “Grimeton Radiostation” menu under
the entry “Så fungerar Alexanderson-sändaren” and at the end there is an excerpt from the DVD-movie
“SAQ, Varbergs Radiostation – Grimeton”. This excerpt contains many details that are very useful
for anyone that is interested in the Alexanderson antenna!

At about 11:40 is the following sentense: “längs symetriaxelns löper en 6,5 mm koppartåd som förbinder
trådarna med varandra och tornens stålkonstruktioner”

This can be translated as that the steel towers are electricaly connected to the ground network.

After having selected using the english language website then in the “Grimeton Radiostation” menu under
the entry “Make a virtual visit to SAQ – Grimeton” and at the end there is “– Antenna tower no 1 from below.”
Zooming in on the tower leg that is closest to the transformer building and power distribution substation
there is visible a metall ribbon bolted to the tower leg and that likely extends into the ground.

From https://de.wikipedia.org/wiki/Alexanderson-Antenne
“Sie besteht normalerweise aus geerdeten Türmen”

This can be translated as that the towers are grounded.

From https://sv.wikipedia.org/wiki/Radiostationen_i_Grimeton
“Denna antennkombination är i praktiken rundstrålande, eftersom den trots sin längd på 2,2 km är kort i
förhållande till våglängden. Till någon del gynnas ändå den nordvästliga – sydostliga riktning som raden
av torn vänder sin bredsida mot i och med att strålningsdiagrammet är svagt elliptiskt.”

However the above text is missing in the english language wikipedia article.
The the text can be translated as that the antenna radiation pattern is weakly elleptical.

A few of the many other useful references aviable:
Patent US1360167 efw alexanderson. – antenna. – application filed sept. 13, 1917. (Use Google!)

“The Electrical Plant of Transocean Radio Telegraphy”

“The alexanderson 200 kw high-frequency alternator transmitter”

Obviously antenna modeling and simulation software was not aviable
to Alexanderson when he filed the patent in 1917. However the design
with the grounded towers apears to have been invented after 1917.

From https://en.wikipedia.org/wiki/T-antenna
“The antenna was used in the powerful radio stations of the wireless telegraphy era
but has fallen out of favor due to the expense of multiple loading coils.”

Umbrella antenna:

References possibly useful for modeling and simulation:

“ELF/VLF/LF Radio Propagation and Systems Aspects” (Use Google to find it!)

Best Regards,
Stefan Johansson