Hi Puddle,
 As far as I have been able to ascertain the ELF system initially used for signalling Submarines in Deepwater, was a forerunner of the HAARP system using the same principals of bouncing signals off the D layer of the Ionosphere.But also able to use the Earths natural magnetic field/Van Allen Belt to increase the range. I believe that it was not a blanket effect Radar where the signal would encompass a wide range at any given time but it was able to be concentrated, directed in effect, in a narrow beam. This is where the possiblity of it being turned into a weapon rather than just Radar came about.
Obviously a concentrated radar beam isn't going to knock out dozens of Aircraft but it was probable that it could have been used on experimental Drones or Enemy aircraft. The HAARP system which followed on from this used several different frequencies including ELF., As below:
http://foia.abovetopsecret.com/ultimate ... ations.pdfJust released in the States under the FOIA.
The Radar was  also reputedly used in Beam Weapon and Plasma Weapon technology which is now apparently old hat.
See the Contents Page.for list of Board members
Project Leader Paul Berhardt. Active Project Leader. Beam Physics Branch. Naval Research Laboratory.
It can also be used in all frequencies including Infra red and Visible.
There was a very big push for Anti Satellite weapons at that time. 140 had been launched in 1980 alone, mostly Soviet and any technology would be trialled to counter them. This was relatively cheap technology which would have appealed to the Military who had been constrained under the Carter Administration. 
And Two other Projects they were trying out.You might appreciate the second one! 
Project SPIKE was a 1970's suborbital conventional warhead ASAT air-launched from an F-106 interceptor. Considerable work was done from the early 1970s under the Missile and Space Defense Program. Research centered on the miniature homing vehicle (MHV) with nonnuclear kill capability. It seems to have lead to the 1980's F-15 launched ASAT of the same concept
Project Early Spring was a conventional ASAT launched by Polaris missiles from US Navy ballistic missile submarines. 
Class: Military. Type: ASAT. Nation: USA. Manufacturer: Lockheed, NRL.
The principle was that the submarine could take a position under the path of the satellite. As it passed overhead, a Polaris missile would be launched with a peak altitude close to that of the target. The ASAT used a restartable upper stage to 'hover' for up to 90 seconds awaiting the satellite. An optical homing system would first locate, then track the target satellite. A datalink was provided to the submarine for control. Once committed, the ASAT would put itself on a collision course with the target. A proximity fuse would detonate a warhead with thousands of steel pellets. To assure a kill, more than one ASAT could be launched simultaneously by the submarine.
Early Spring was first presented to Congress in March 1961. By 1964 several alternate configurations were evaluated, and by the late 1960's the optical tracker was showing good results in tests. The project was officially cancelled in the late 1960's. However the same concept can be found in the Navy's manned Space Cruiser concepts of the early 1970's and 1980's.