Saglek BMEWS Communications AN/FRC-39 Antennas

Billboard Antennas

The antennas used for transmission and reception were known as "Billboard" or "Sail" antennas. The antennas pointing south toward Hopedale were 120 feet in diameter and those pointing north toward Resolution Island were 60 feet in diameter - indicative of the relative distances to those sites. The antennas were roughly square in appearance although the reflecting surface was in fact parabolic. The antennas were fully enclosed and the interior was heated by an oil furnace to keep ice from forming on the reflecting surfaces. Feed horns (electrically heated) were mounted on separate towers in front of the antennas. Close-up pictures of the antenna surfaces are rare because the radio frequency power being radiated was at least ten times higher than a microwave oven and so the most sensible of us stayed at a respectable distance.

The first picture shows all four of the Saglek antennas. North is to the right. The second picture shows the face of one of the 120 foot antennas, and the third picture shows one of the 120 foot antenna feed horns and the waveguide enclosure conveying the transmitted and received signals.

The following technical description (corrected for one small error) was contributed by David Davies who also served at Saglek in the 1960's and 1970's:

The sail antennas (at Saglek) faced Hopedale and Resolution, there were two in each direction. Each sail was fed from a 10KW transmitter, One was polarized horizontally and the other vertically. Each transmitter was on a different frequency, and the sails were placed at least 100 wavelengths apart. Each station therefore had quadruple diversity reception, space diversity, frequency diversity. polar diversity, and scatter angle diversity. This ensured good reception most of the time as each of the four parametric amplifiers was receiving a different phase.