two newbie questions (radar and navigation)

[Stealhead]

It is aid that the SJ could read planes if they where at low level 500oft or less but they also had to be pretty close about 8 miles but that just happened sometimes you could not rely that the SJ would pick up a plane at low level. I dont belive though that the SD or SV would have read ships ever unless they where in the sky they where desigined to send the radar beams skyward.