ADVISORY MINIMUM SPECIFICATION^ FOR MARINE LORAN 

 RECEIVER-INDICATOR EQUIPMENT 



General. — These minimum advisory specifications are intended for the use 

 of mariners interested in Loran receiving equipment for all types of vessels. 



Application of Equipment. — The equipment herein specified shall be capable of 

 furnishing accurate navigational information when used aboard vessels in 

 Loran service coverage areas. It must be capable of being operated and 

 accurate readings taken by persons having had limited training in its use. 



Ala/or Items of Equipment. — The entire equipment normally shall consist of the 

 three component parts listed below : 



(a) Receiver. 



(b) Indicator. 



(c) Power supply. If a separate power unit is provided, it is necessary 



that the connecting cable not contain high current leads which 

 would limit the length of cable to a specific value. 



The first two components should be included in a single package. A sep- 

 arate power supply is optional. 



Physical Limitations. — For larger type vessels the equipment may be table, 

 bulkhead, or deck mounted. For smaller craft the equipment should be as 

 light and small as practicable, table or shelf mounting is recommended. The 

 equipment should be rugged and designed in accordance with standard prac- 

 tice for electronic equipment for shipboard installation. 



Receiver circuit. — Wideband superheterodyne capable of handling a 40 micro- 

 second pulse width minimum distortion. 



Frequency Range. — 1800-2000 kc; 2 switch-selected channels having discrete 

 frequencies of 1950 and 1850 kc. The channels shall be marked: 1-1950, 

 2-1850. At least one spare RF channel shall be provided for 1900 kc. 



Radio Frequency Tuning Stability. — The over-all radio frequency tuning stability 

 shall be such that the center of the pass band will not deviate more than plus 

 or minus 5 kc. from the channel frequency over the range of temperature 

 and humidity specified. 



Heterodyne Oscillator. — For each discrete frequency the frequency drift of the 

 oscillator shall not exceed plus or minus 1 kc. over specified ranges of supply 

 voltage, ambient temperature and relative humidity. 



Bandwidth. — 45 kc. over-all plus or minus 5 kc. at 6 db down and not more 

 than 180 kc. over-all at 60 db down on all radio frequency channels. 



Over-all Sensitivity. — Deflection On scope — 1 inch for 3-inch tube, or 1^4 inches 

 for 5-inch tube for receiver input of 8 microvolts peak or less. Ratio of signal 

 to internally generated noise — at least 3/1. At least 10 db additional gain 

 to be provided, irrespective of signal/noise ratio. 



Signal Amplitude Balance Ratio. — Continuously Variable from 1/1 to 1000/1. 



Maximum Signal Input Voltage. — Ten volts peak input to receiver terminals. 

 A switched fixed attenuator may be employed in order to obtain the required 

 range of gain. 



Interfering Frequencies. — (a) As measured at the receiver terminal, inter- 

 fering signals shall exceed the desired signal to provide equal and standard 

 outputs by at least the following values: 



Intermediate frequency 70 db 



Image frequency 75 db 



(b) At other frequencies, interfering signals shall be attenuated according 

 to the below selectivity curve: 



Total bandwidth db 



45 (plus or minus 5 kc) 6 



90 minimum 20 



130 40 



180 60 



250 80 



65 



