Малая радарная система
The first Small Radar built puts one unit in your bases's "Short Range Detection" meter, and helps with UFO Detection. Further Small Radars also add to the meter, but do not increase the detection rate.
Every thirty minutes of game time, each base with a Small Radar has a 10% chance of detecting a UFO within an approximate 1300-1500 mile radius (this may also vary based on UFO size), and can track existing contacts up 2000 mile radius. If you advance the time an hour or day at a time, it will make multiple checks and interrupt if a UFO is detected, setting the time to be at whatever point the detection happened (even if it is only five seconds after the last update).
Whether these chances are affected by the size of the UFO is unknown, the UFOpedia suggest that it does play a part, but the description text is wrong about all the other details.
You cannot gain increased detection by building more Small Radar facilities at the same base, but you can add a single Large Radar System to boost your total detection rate from the base to 30% at short range and 20% at long range. Any more radars of either type have no game effect, except on the detection meters on the Base Information page. Both types of Radar become redundant once a Hyper-wave Decoder has been installed at a base.
Please only use the following as a guide, you may find that just inside or outside the circle you can get/maintain detections. Remember once you have spotted a UFO you can normally only lose tracking of it on the stroke of a half hour, so fast UFOs might sometimes still be visible when outside this radius by a significant margin (i.e. they can get to Nigeria, India, and similar extents in some cases)
Note the base in the image is located slightly SE of Budapest (at the base between the E and S when zoomed in the maximum). Note that the outer ring is based on the extents that a UFO can be tracked to, the detection radius seems to be only 67-75% or so of this range, but this may vary according to the UFO size (needs determining). Ranges may also vary according to the latitude that bases are built at (needs checking).
Construction Time: 12 days
Construction Cost: $500,000
Maintenance Cost: $10,000/month
The above detection abilities are one-time-bonuses per base. The base detection values are recalculated every time a new building is completed on a base.