The following report on the WW2 SO-7M truck-mounted surface search radar was published in the September 1944 issue of C.I.C. (Combat Information Center) published by the U.S. Office of the Chief of Naval Operations.
What the SO-7M can do…
The SO-7M—a truck mounted surface search radar with PPI presentation—is being furnished to Marine Corps Units and Naval Surface Search units. A performance test of the set tinder typical conditions was conducted by the Pacific Fleet Radar Center.
The SO is mobile.
The SO-7M was sited on the shoreline with its antenna 20 feet above sea level. A 100 degree sector to seaward, with no line-of-sight obstacles, provided adequate area for the test. No difficulty was experienced in putting the equipment into operation. The time required for two men to do this was only about 15 minutes. The set appeared to be in excellent materiel condition.
A compact set.
At any time during the day, 5 to 10 plane contacts could be seen. Most of these gave E2 to E3 contacts out to 30,000 to 35,000 yards, and one even gave an E4 echo at 40,000 yards. The maximum range on large ships was about line of sight distance. Several masts were detected while the ship targets were hull down. Minimum range was checked on flying boats that taxied near-by and on small buoys that stood a foot out of the water. The actual minimum range was definitely less than the theoretical minimum. The ranges were over water and could not be checked but could not have been much over 100 yards. Echoes of E4 strength gave contacts about 7 to 8 degrees in intercept and bearing resolution was good.
The following performance data was compiled:
Type of Target Range Target Angle E Strength Tug 15,000 Yd. 3 CVE 30,000 Yd. 3 2 DD’s 30,000 Yd. 2 CVE & 2 DD’s 18,000 Yd. 4 AK 15,000 Yd. 2-3 CV (?) 37,000 Yd. 1 LST 15,000 Yd. 3 Tug 26,500 Yd. 1 2 Seagoing Tugs 19,000 Yd. 135 2 2 LST’s 10,000 Yd. 135 3 DE 14,000 Yd. 270 2 DE 9,500 Yd. 270 2-3 DE 10,000 Yd. 180 2 AO 19,000 Yd. 270 4 LST 6,000 Yd. 090 4 PT 4,300 Yd. 090 3 PT 4,500 Yd. 135 2-3 Tug 8,000 Yd. 220 3 AK 30,000 Yd. 080 3 (?) 54,000 Yd. … 1-2 Plane (S) 36,000 Yd. … 1-2-3 “ 10,000 Yd. … 1
The SO-7M/N was used by USMC Anti-aircraft battalions landed on Okinawa at a rate of one per Battalion.