SP-600 DESIGNATION'S PRODUCTION    SUFFIX #         NOTES DATE Sept. 1951            SP-600-JX-1         Std. frequency range 540 Khz - 54 Mhz.                                                                Also designated R-274A/FRR (family of                                                                Radios) Signal Corps order no.                                                                             1689-Phila-51-01. Sept. 1951            SP-600-JLX-2        Std. frequency range 100 - 400 Khz,                                                                     1.35 - 29.7 Mhz. Sept. 1951            SP-600-J-3            Std. frequency range, 540 Khz - 54                                                                        Mhz. No Xtal frequency  control. Sept. 1951            SP-600-JX-4          Std. frequency range 540 Khz - 54                                                                        Mhz. No Xtal frequency control. Signal                                                                  Corps. R-320A/FRR. Order no.                                                                             19474-Phila-50-06. Also has separate                                                                    IF gain control. Nov. 1951             SP-600-J-5            Std. frequency range, 540 Khz - 54Mhz.                                                                equipped with 25 cycle(hertz) power                                                                      supply. Signal Corps. R-483/FRR.                                                                         Order no. 21478-Phila-50. Sept. 1951            SP-600-JX-6          Std. frequency range, 540Khz - 54Mhz.                                                                  BFO range 0-10Khz. U.S. Navy model                                          R-274B/FRR. Order no. Nobsr-52039. Sept. 1951            SP-600-JX-7          Std. frequency range. 540Khz - 54 Mhz. Sept. 1951            SP-600-JX-8          Std. frequency range .540Khz - 54Mhz.                                                                  Manufactured for Welch contract no.                                                                     -XG-479. Sept. 1951            SP-600-JL-9           Std. frequency range, 100 - 400Khz,                                                                      1.35 - 29.7Mhz. No Xtal  frequency                                                                        control. Sept. 1951            SP-600-JX-10         Std. frequency range, 540Khz -                                                                             54Mhz. Replaces JX-7. Nov. 1951             SP-600-J-11            Std. frequency range 540Khz - 54Mhz.                                                                  No Xtal frequency control. Note: This                                                                    model made to complete NAVY order,                                                                  without the  changes per ECN1156 as                                                                   standard J series. Replaces J-3. Nov.  9,  1951       SP-600-JX-12          Std. frequency range, 540Khz -                                                                              54Mhz. Signal Corps. R274A/FRR,                                                                       order no. 3376-Phila-52. Replace JX-1. Nov. 26, 1951       SP-600-J-13             Std. frequency range, 540Khz -                                                                              54Mhz. No Xtal frequency control.                                                                         Signal Corps. order no. 16838-Phila-                                                                     51. Serial no's 52 - 67 inclusive. 25                                                                        cycle power supply. Replaces J-5. April 23,  1952       SP-600-JX-14          Std. frequency range, 540Khz -                                                                              54Mhz. Signal Corps. R274C/FRR,                                                                       order no. 3376-Phila-52. Replaces                                                                         J-10. June 17, 1952       SP-600-JLX-15         Std. frequency range, 100 - 400Khz,                                                                      1.35 - 29.7Mhz. Replace JLX-2. June 17, 1952       SP-600-JL-16            Std frequency range, 100 - 400Khz,                                                                       1.35 - 29.7Mhz. No Xtal frequency                                                                         control. Replaces JL-9. June 17, 1952       SP-600-JX-17            Std. frequency range, 540Khz -                                                                              54Mhz. Diversity receiver                                                                                       manufactured for Air Material                                                                                 Command. Note: easily  identified by                                                                    " Red Knobs." June 26, 1952       SP-600-JX-18            Std. frequency range, 540Khz -                                                                              54Mhz. Made for "GAUVREAU"                                                                           contract. Replaces JX-10. Aug. 27, 1952        SP-600-J-19             Std. frequency range, 540Khz -                                                                              54Mhz. No Xtal frequency control.                                                                         Equipped  with 25 cycle power supply.                                                                   Replaces  J-5, J-13. Aug.  1952             SP-600-JX-20           Std. frequency range, 540Khz -                                                                              54Mhz. No Xtal frequency control.                                                                         Same as J-19. Signal Corps.                                                                                 R483A/FRR, order no. 3479-Phila-52.                                                                   Equipped with 25 cycle power supply.                                                                    Replaces J-19. Feb. 13, 1953        SP-600-JX-21           Std. frequency range, 540Khz -                                                                              54Mhz. Replaces JX-10. Feb.  1953             SP-600-J-22              Std. frequency range, 540Khz -                                                                              54Mhz. No Xtal frequency control.                                                                         Replaces J-11. Feb. 1953              SP-600-JLX-23          Std. frequency range, 100 - 400Khz,                                                                      1.35 - 29.7Mhz.  Replaces JLX-15. Feb. 1953              SP-600-JL-24            Std. frequency range, 100 - 400Khz,                                                                      1.35 - 29.7Mhz. No Xtal frequency                                                                         control. Replaces JL-19. Feb. 1953                 SP-600-J-25            Std. frequency range, 540Khz -                                                                              54Mhz. Equipped with 25 cycle                                                                              power supply. Replaces J-19.                         CONTINUE