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Loran-C station equipment in the the U.S. West Chain 9940 Lorsta "Searchlight". This is one of several  "dual rated" stations in the Loran chain.The USCG prefixes its Loran station names with Lorsta which is a contraction of the words Loran and station (Photos courtesy USCG).


Some transmitters in a Loran chain have only one function. That means they either serve as dedicated master or dedicated secondary station in a particular chain.  Many transmitters, however are dual rated,  meaning that these can serve one function in one chain and yet another in a neighboring chain. For example, the Lorsta Searchlight  (Nevada) facility has a transmitter which serves as the secondary (Y) station in the 9440 chain and it also serves as the secondary (W) station in the neighbouring chain 9610. Dual rating is desirable because, other things being equal, land acquisition costs and siting difficulties are reduced.

In a dual rated environment, the operations/timing room has dual timing systems which are common to one transmitter. Both timing systems operate from the same cesium frequency standard, thus helping to reduce equipment cost. There is not one but two electronic timers for each rate. For each rate, one timer is always on-line while the other serves as a standby unit.

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DUAL RATES: These maps of chain 9610 (left) and 9940 (right) serve to illustrate their coverage area. The dual rated station Lorsta Searchlight (Nevada) is used as the secondary (W) in chain 9610 and secondary (Y) in chain 9440. (Graphics courtesy of USCG).

The Canadian East Coast chain 5930 has one master and three secondaries. All four stations are dual rated.

Here is an example of a current (2001), state-of-the-art solid state Loran-C transmitter. This is the Model A6500 manufactured by Megapulse Inc (Photo courtesy of Megapulse Inc).


Coverage: This map illustrates the global coverage of Loran-C. (Graphic courtesy of Eurofix web page).


Back to Loran-C Intro Page

Sept 24/06