A Review and Applications of VLF and LF Transmissions for Navigation and Tracking

Abstract

a review of existing Very Low Frequency and Low Frequency transmissions that can be used for navigation, position and location, tracking and rendezvous is given. This includes the USSR Loran–C system, the USSR Very Low Frequency navigational aid (VLF), the international Omega system, the U. S. Navy VLF communications system, and those transmissions employed in the international time dissemination network. The characteristics of these various systems are discussed in relation to various applications. The potential and limitations to accuracy of the various systems are presented. A number of applications are described. In particular, the use of retransmission techniques for positioning of remote objects and differential techniques for enhancing accuracy are discussed. A piece of equipment is described which has been designed to utilize signals transmitted by the various navigation systems and an intermix of these transmissions. The simultaneous use of two or more systems to remove ambiguity and determine absolute position is described. The paper concludes that the VLF and LF transmissions are compatible and should co‐exist and are not necessarily redundant. Several references are given which include descriptions of the various systems and studies that have been performed analyzing and comparing performance.

Omega Windfinding and GATE

“…The third source of phase error is unwanted signals from other transmitters. Beukers (1973) detected transmitters radiating at about 11.9, 12.6, 14.9, 15.1, and 16.0 kHz in Dakar. Most of these are much stronger than the Omega signals and care must be exercised in dealing with them.…”

“…However, the basic analytical ideas developed below can be applied to utilize other transmitters in the VLF band, DECCA, or LORAN-C near 100 kHz. Beukers (1973a) established the VLF signal strength environment in Dakar. Of particular interest for windfinding during GATE, there are the Omega transmitters between 10.2 and 13.6 kHz, a USSR transmitter in Krasnodar at 11.905,12.649,and 14.881 kHz, and the very powerful transmitters in Rugby, England (16 kHz), Cutler, Maine (17.8 kHz), Jim Creek, Wash. (18.6 kHz), and Balboa, C.Z.…”

Low-Frequency Correlation Phase Detectors Using Hard Limiting

“…Detector circuitry can often be further simplified by using signals other than sinusoids as the locally generated reference signal in a correlationtype phase detector. Consequently, several quasi-correlation concepts [1][2][3][4][5][6][7][8][9] have been developed for use in lowcost radio navigation receivers and in retransmitters for remote position finding and tracking [10,11] . Similar detectors are used in sonar [12] , phaselock, synchroniza;tion, and other [13] applications.…”