The Naval Radio Transmitting Facility Annapolis, Maryland (on salty
Chesapeake Bay) had a similar system in use up till about 1976.
It was used for broadcast only to the Mid-Atlantic Navy Sub fleet.
Apparently, there were at least a dozen of these
type stations constructed around the globe to facilitate world wide sub
communications. The Annapolis station
was tuned to 38Khz, if I remember correctly. Had a 1200ft tower and nine
600ft support towers, with a TOPHAT antenna
array. The LF transmitting equipment consisted of (three each) keyers,
Intermediate Power Amplifiers, Power Amplifiers,
A Delta Matrix antenna switch assembly, one 800 foot tower and one
Marconi (Triatic) array. The final output was about
1M watts but by the tine it go to the tower it was down to about 300Kw.
The Helix house had three feeders that coupled RF directly to the 1200ft
tower at 300ft, 600ft, and 900ft. The feed lines were composed
of cable made from number 22 gauge enameled wires bundled to create
cables that were about 6 inches thick. Each of
the feeders was composed of four of these 6 inch cables. The download
weight of the TOPHAT was about the same as that
of a fully loaded US Battle ship. All that a state on top a array of
insulators at the base of the 1200ft tower. The input impedance was
also very low and in fact the Navy had to go to narrow shift keying
because the bandwidth of the antenna was so narrow.
That station is still in tack and EPA regulations will not allow for the
demolition (too much lead paint --Chesapeake Protection Act)
so the Navy is entertaining ideas which include leasing the facility to
Cellular companies and creating a historical site which may include
the option for amateurs to hook up to the Marconi antenna and operate
portable! Might be a hell of a 160 ant, HAHA.
later,
dave
p.s. This recantation was all from memory of a tour I took of the
facility a few years ago so please excuse if I didn't get it perfect.
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