Project Sanguine - Project ELF

Project ELF

The scaled-down system the Navy eventually constructed, called Project ELF, began testing in 1982 and became operational in 1989. It consisted of two transmitter facilities, one at Clam Lake, Wisconsin and one at Republic, Michigan. with a total of 84 miles of above-ground transmission line antenna. The two transmitters normally operated synchronized together as one antenna for greater range, but could also operate independently. The scaled down system was not designed to survive a nuclear attack.

The Clam Lake facility, which served as the test site and was originally called the Wisconsin Test Facility (WTF) consisted of two 14-mile (24 km) transmission line antennas (called ground dipoles) in the shape of a cross, with the transmitter station at their intersection. The Republic facility consisted of three transmission lines, two 14-mile and one 28-mile, in the shape of the letter "F" (the shape is not significant and was dictated by land availability). The lines, made of 1.5 cm aluminum cable supported on insulators on 40 ft. wooden utility poles, resembled ordinary power transmission lines. The ends of the transmission lines were grounded by 1 to 3 miles of buried copper cable and ground rods, later replaced by arrays of electrodes in deep 300 ft. boreholes The transmitters sent alternating currents of 300 amperes through the lines, which passed through the buried electrodes deep into the Earth.

The transmitters operated at a frequency of 76 Hz in the extremely low frequency band, with an alternate capability at 45 Hz and used a combined power of 2.6 megawatts. They were able to communicate with submarines over about half the world's surface. The system transmitted continuously, 24 hours a day, sending an "idle" message when it was not being used.

Because of the extremely small bandwidth of the ELF band, the transmitters had a very slow data rate. They couldn't transmit voice (audio) but only short coded text messages of a few letters. Reportedly it took 15 minutes to transmit a single 3 letter code group. Therefore the system was not used to relay operational orders, but served a "bell-ringer" function, ordering specific submarines to the surface to receive detailed orders by ordinary radio and satellite communications links.

The system was controversial, and was the target of legal attacks, suits and protests throughout its operating life. On five occasions protesters cut down transmission line poles, interrupting operation briefly.

In 2004 the Navy shut down both transmitters, with the explanation that very low frequency (VLF) communication systems had improved to the point that the ELF system was unnecessary.