There are quite a few radar sites and ground threats in the valleys and hills south and west of Cedar Gate Road, as well as mobile radar sites around the gate itself. Two of them are unusually large, considering there is no regular air traffic anywhere around. At least none that we know about...
As it turns out these radar sites are mostly Russian models. They are part of a test range for new stealth developments that operate out of Area 51 or in a later stage out of TTR. The location, between Area 51 and TTR and almost in a straight line with the north end of the Groom runways, in an uninhabited valley makes this an ideal spot for such tests. There are similar mobile sites near the Area 51 North Gate (see link below). On several occasions we have observed tests at night, involving both radar locations. The sites are also used as threat simulators during Red Flag exercises.
Update 4/2006: A Russian Fan Song radar site for Fire Control and Target Tracking. It can track up to six targets simultaneously at a range of 60-120km. Its typical use is in connection with an SA-2 SAM site and a SPOON REST target acquisition radar. Photo by Hank Shaw, with friendly permission.
This one is a Russian "PRV-11 SIDE NET" height finding radar, similar to the one at the Area 51 North Gate. It was designed for use with the Russian "S-200 SA-5 GAMMON", which is a medium to high altitude surface-to-air missile system. It is also used with the SA-2/3 SAM. It has a range of 28 km and a max. altitude of 32 km. The radar operates in the E-band.
The red and blue warning lights on top of the ramp indicate when the site is active. Thanks to our reader Bryan Coish for identifying the system.
More radar sites in the vicinity of Cedar Gate, photographed in September 2001. Both are located in the northern Kawich Valley, southeast of Cedar Gate.
Update 03/2020: A massive new 6-story antenna tower was constructed at the Ragged Ridge radio site in late 2019 or early 2020. As of 03/2020 it only has some vertical dipole antennas on top, most of which have been moved up there from the top of the building. But due to its size it is likely designed to hold new microwave dishes or other equipment in the future.
The radar to the left and below is very similar to the one above, but located north of Tonopah. The site there is on public land, but marked: "US Government Property. No Trespassing". The dish there is pointed southeast, again towards TTR.
This is of course an interesting design: Imagine a ring of antennas, each one directional, facing away from the center of the circle. If you poll them with the electronics box in the center doing a time multiplex, you essentially have a very fast rotating 360 degree radar without any moving parts, and with a high resolution and fault tolerance due to overlap of the segments.
This design appears to be a Doppler Direction Finder. A Doppler Direction Finder works by quickly switching between receiving elements, thus virtually rotating an antenna. By doing this, and measuring the shift in the received frequency, it is possible to calculate the direction of an incoming signal. By linking several of these systems in different locations it is possible to calculate a positon fix for a transmission. Most likely the units are tuned to UHF transmissions of military aircraft. They may be used to test the susceptibility of (test-)aircraft to passive radiolocation techniques.
Any further input on these systems is greatly appreciated. All photos taken in September 2001.