Hi Pistoliero,
With map contacts on, as I recall radar contacts show up on the map as gray square icons. You can test this at the beginning of a mission while sitting in harbor.
http://uboat.net/technical/radar.htm
The early radar array was fixed and mounted to the front of the conning tower. It could "see" about a 60 degree arc in front of the uboat.
In Silent Hunter 3, radar is virtually useless.
First of all, it turns off every time water hits it. So in low visibility, such as bad weather, when you want to use it most of all, it is getting hit by crashing waves and turning off.
The upgraded set with the rotating antenna is better in this regard, being higher above the water, but it is still useless.
With map contacts
on, you will get directional arrows pointing to radar
sources far sooner and with more accuracy than you will get radar
contacts from your own radar set. You basically get little gray lines pointing to the source of the radar source, just like you get for sonar contacts. So with map contacts on, your radar warning device actually acts almost like radar except it is far more accurate.
Also, your own radar, as you note, gives away your position and will have escorts come looking for you.
With map contacts
off, the radar is super-useless.
Only on very, very rare occasion have I had my radar operator tell me, "Radar contact, bearing XXX!" Most of the time he is completely silent about any radar contacts. I think this is probably a bug.
And, unlike the sonar man, you cannot ask the radar man for "nearest contact".
And with radar, it is the one tool where you would expect to get accurate range and bearing information and, logically, display this on the map. Of course, with map contacts off, you don't get that information.
So the only way to get any radar data is to operate the equipment manually by pressing the R key.
Unfortunately, it is VERY hard to operate and get a contact, though it can be done. All of the radar sets in SH3 have oscilloscope displays. The Type XXI is supposed to have a PPI display (the sweeping line and dots) but it does not.
With the oscilloscope display, you have to first turn on the unit. You then see a vertical band of squiggly lines (background noise). You can change the range of the unit to long or short range. When you get a "hit", a "spike" appears in the squiggly lines. This is your radar return. It's position indicates range according to the displayed scale.
You turn the radar by using the wheel and clicking on either the left or right side of the wheel to turn the radar left and right. Unfortunately it is hard to see the bearing indicator when doing this. Also, frustratingly, it is very, very hard to turn the wheel left and right and get it to actually stop on a contact.
Try it. Sit in your harbor and try and get contact information on the ships you see around you. It's very hard. I figure by the time I get any useful information from it I've already broadcast my presence and then some.
Steve