LORAN

There is a limit to the accuracy with which the relative timing of radio pulses can be measured. For greater precision, pulses need to have a very steep wavefront. That is, they must start very quickly. Pulses with steep wavefronts must have a high harmonic content, and this means that the transmitted signals will have sideband components far to either side of the assigned frequency. The LORAN signals must be confined within a fairly-narrow band of frequencies to avoid interference with other services, and this limitation blurs the definition of the start of each pulse. The result is a compromise in the accuracy of measurements of pulse timing.

There is less variation in the radio-signal propagation path taken by LORAN C signals at 100 kHz, but there are path variations that cannot be measured. The effect is to further reduce the quality of the information available to the LORAN computer. These effects are small, but they nevertheless set a limit on the available precision of navigation information that can be obtained from LORAN techniques.