JRC

Appendix 2
Published Radar Parameters

         This Appendix summarizes the published behavioral characteristics of the JRC product line, principally as publicized by the manufacturer.

Table 1 lists the systems in the present-day product catalog, with a grid showing which listed pulsing rates may used by the system,  and what PD or PDs may be used with that tabulated pulse rate. It should be borne in mind, when viewing this table, that:  

  • The system names are not exhaustive; product-line designations have been condensed, replacing the last two digits of their nomenclatures with 'xx';     
  • Where multiple PDs are shown for a given PRF, these represent factory-determined settings for individual systems, rather than operator-selectable alternatives. Ordinarily, individual systems will have no more than four PDs available, in the range 0.07 to 1.2 uS, and selection of PD is by changing range-scales.
  • There may be more PRFs listed for a product line than are available to any one specific installation.   
Table 2 summarizes the antenna behaviors of the JRC product line by cross-indexing scan rate with antenna system. Liberties have been taken in compiling this table, for the sake of readability.  The following should be borne in mind:
  • Documentation is inconsistent. In some cases, a scan rate of either 21 or 26 rpm is given, for either 50 or 60 Hz ship's power-supply frequency; in some other cases, the scan rate may be reported only as "26 rpm (60 Hz)." In the latter instance, this has been taken to imply that a 21-rpm rate would be used when a 50-Hz power supply is used.      
  • Similarly, in one instance (the JMA-7736), a 17-rpm scan is reported with a 60 Hz mains supply frequency. In this case, a 14-rpm scan is assumed for a 50-Hz mains supply frequency. 
  • There is both documentary and anecdotal evidence that some smaller systems (i.e. 6-kW radars) have several unpublished scan rates:  

o   Installation manuals allude to 'slow', 'normal' and 'fast' rotation speeds, associating them with radar range-scale selection, but without providing any figures.            

o    "Powerboat Reports," a consumer magazine for power-craft owners, in its May 2006 edition, discusses a disabled 'S Buoy' mode in which non-radome JRC antennas may rotate substantially more slowly than normal, to increase detection ranges on small buoys.      

o   The control for the 'S Buoy' mode is mentioned in some instructional literature developed by JRC, without providing any specific data.  In some of this literature, reference is also made to a 'fishing-net' mode, designed to improve detection ranges of the small floats commonly used in demersal fishing.

Taking these into account, and also the manufacturer's explicit statement (in materials for the JMA-5104), that antenna-speed switching is "disabled because it uses a radome," it is projected that the JMA-5106 has at least two other unpublished scan-rates, as may the JMA-2344, JMA 3806 and the JMA-3910.

Table 1
Transmission Characteristics

Table 2
Antenna Systems