Explanation: The secondary stations blink to notify the user that a master secondary pair is unusable. Blink is repetitive on/off pattern of the first two pulses of the secondary signal.

Explanation: There are some Loran-C users who do not employ Loran-C in a hyperbolic mode but rather in the direct range rho-rho-rho mode. The rho-rho-rho process involves a minimum of three transmitter stations and the use of an iterative computation to obtain fix.

Explanation: Direct ranging Rho-Rho mode requires a minimum of two stations, a highly stable user frequency standard and precise knowledge of the time of transmission of the signal. The use of this mode is limited by the high cost of stable frequency standard.

Explanation: The corrections using differential Loran-C are generally valid for the co-relation distance of approximately 100 miles from the reference station. Real time co-relations remove both seasonal and diurnal errors can be broadcast.

Explanation: In Millington’s method, the signal between the transmitter and the receiver is broken down into finite segments of different conductivity levels, based on conductivity maps. The incremental phase delay is then computed as a function of range and conductivity for each path segment summed and averaged to provide an estimate of ASF.

Explanation: Each transmitter station is physically divided into two groups of units to provide system redundancy. At the appropriate interfaces switching units are provided between them.

Explanation: Dual redundant pulse amplitude and timing controllers or PATCO accept timing signals from the timer and derive from this all the signals needed by the transmitter. Signals generated by the PATCO include start triggers, charging triggers, digital amplitude reference signals, amplitude compensation signals, and megatron reference trigger.

Explanation: In the Omega system, each station transmits continuous wave signals on four common frequencies and one station unique frequency. The signal frequencies are time shared among the stations so that a given frequency is transmitted by only one station at any given time.

Explanation: Each HCG or half-cycle generators contributes to the power contained in the Loran-C pulse. 32 HCGs comprises the standard set. The basic set can be expanded in multiples of eight HCGs.

Explanation: Loran-C signal reception can be impaired by interference from other signal broadcast on slightly different frequencies. To avoid degradation of S/N associated with these interfering sources, Loran -C sets are equipped with notch filters.

Explanation: At each Omega station, continuous wave signals on four common frequencies and one station unique frequency. The signal frequencies are time shared among the stations so that a given frequency is transmitted by only one station at any given time.

Explanation: Since the Omega stations transmit in very low frequencies, the antennas are the largest physical structures in the stations. Three types of antennas are employed in the Omega system: grounded tower, insulated tower, and the valley span.

Explanation: The RF signal that is to be transmitted is transferred to the ‘Helix,’ a large helical coil that acts as a coarse tuning device for the antenna. The helix is equipped with separate taps for each signal frequency transmitted.

Explanation: A typical Decca chain consists of a master station and three slave stations. A station has a 2kW crystal controlled transmitter feeding a 300ft antenna.

Explanation: Chayka is a pulse phase radio navigation system similar to the Loran-C system. By using ground waves at low frequencies, the operating range is 1000mi and by using pulse techniques, sky wave contamination can be avoided.