de WB2CPN Never saw 90/150 on an ILS Marker, 3000 maybe. What was name of CAA Localizer, and their VAR? By then all L/R Blue/Yellow was 90/150, wasn't it? Freqs chosen because of the relations of their harmonics. Also, 90 was made by a three-bladed chopper, 150 used a five-bladed chopper. Talking coax bridges. EOT (End of Trivia); 73 Clete